💾 Archived View for mirrors.apple2.org.za › archive › www.textfiles.com › apple › ANATOMY › cmdread.… captured on 2024-08-19 at 03:01:52.

View Raw

More Information

⬅️ Previous capture (2023-01-29)

-=-=-=-=-=-=-

	
:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=*

	
NOTE:  Normally, execution flows back into Applesoft.  When    *

	
Applesoft picks up a subsequent INPUT or GET statement, *

	
data is retrieved from the disk because the READ cmd    *

	
was exited with OPUTCOND: $00 and CONDFLG: $01.  An     *

	
example of program flow is shown below for an INPUT     *

	
statement.  Our illustrative disassembly begins in      *

	
Applesoft after it has recognized the INPUT tolen and   *

	
jumped to the beginning of that routine.  Not that      *

	
this disasseembly is over simplified and not complete.  *

	
(For instance, it does not include multiple variable    *

	
input.)  Furthermore, it is definitely NOT meant to     *

	
describe the inner workings of Applesoft.  Instead the, *

	
intent is merely to provide a specific example of how   *

	
an INPUT statement becomes interconnected to, and is    *

	
processed by, those nebulous DOS creatures called       *

	
condition handlers.  Assembly language programmers who  *

	
use GETLN ($FD6A) to retrieve data from the disk may be *

	
particularly interested in the non-Applesoft portions   *

	
of this disassembly.                                    *

	
:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=:=*




(DBB2)
INPUT    CMP #' '     ;Is there an optional input string?
                      ;(Such as in: '100 INPUT "WHAT IS YOUR NAME";A


)
(DBB4)   BNE NOPTNSTR ;Branch if no optional input string.
         JSR STRTXT   ;Make text from the string.
         LDA #';'     ;Make sure that there is a semicolon after
         JSR SYNCHR   ;the optional string, else issue error message.
(DBBE)   JSR STRPRT   ;Print the optional string prompt.
                      ;Note:  Goes through DOS hooks via OPUTINCP and OPUTHNDL0.
(DBC1)   JMP CKDIFRD  ;Bypass printing of the "?" prompt when
         -----------  ;using optional string prompt instead.

(DBC4)
NOPTNSTR JSR OUTQUES

                      * CONDITIONALLY PRINT THE INPUT "?" PROMPT.
                      (DB5A)
                      OUTQUES  LDA #'?'
                      OUTDO    ORA #$80     ;Convert to neg ASCII.
                               CMP #" "     ;Is it a ctrl char.
                               BCC GODOPUT  ;Branch if ctrl char.
                               ORA FLSHMSK  ;$40 for FLASH, $00 for INVERSE or NORMAL.
                      GODOPUT  JSR COUT     ;Go to output handling routine.
                      (DB64)

                                            (FDED)
                                            COUT     JMP (CSW)
                                                     ---------

                                            * DOS'S output intercept routine.
                                            (9EBD)
                                            OPUTINCP JSR PREP4DOS

                                                                  * Prepare for processing by DOS.
                                                                  (9ED1)
                                                                  PREP4DOS STA ASAVED   ;Save (a), (y) & (x) registers.
                                                                           STX XSAVED
                                                                           STY YSAVED
                                                                           TSX          ;Adjust stack pointer and save it so that
                                                                           INX          ;when later restore it and hit an "RTS",
                                                                           INX          ;we can return to the routine that
                                                                  (9EDD)   STX STKSAVED ;called the routine that contained
                                                                                        ;the "JSR PREP4DOS" instruction.
                                                                                        ;(In this case, set to rtn to $DB67.)
                                                                  (9EE0)
                                                                  UNCONDOS LDX #3       ;Handy entry point frequently used by
                                                                                        ;assembly language programmers to
                                                                  (9EE2)                ;disconnect DOS completely.
                                                                  SETRUHKS LDA CSWTRUE,X ;Restore the I/O hooks to point to the
                                                                           STA CSW,X    ;true I/O handlers, ex:
                                                                           DEX          ;   KSWTRUE: KEYIN --> KSW: KEYIN.
                                                                           BPL SETRUHKS ;   CSWTRUE: COUT1 --> CSW: COUT1.
                                                                  (9EEA)   RTS          ;4 bytes (0 to 3) to move.

                                            * Use current OPUTCOND value to index table containing
                                            * address of output condition handlers.  Do a "stack jump"
                                            * to the appropriate condition handler entry point.
                                            (9EC0)   LDA OPUTCOND
                                                     ASL          ;Times 2 cause 2 bytes per address.
                                                     TAX          ;Set (x) to index table of entry point addresses.
                                                     LDA OUTHNDTB+1,X ;Put adr of output handler on stack
                                                     PHA          ;(hi byte first) and then do a "stack jump"
                                                     LDA OUTHNDTB,X ;to the appropriate entry point.
                                                     PHA
                                                     LDA ASAVED   ;Get char to be printed.
                                            (9ED0)   RTS          ;Execute the "stack jump"

                                                     .
                                                     .
                                            STACK JUMP TO OPUTHDL0
                                                     .
                                                     .
                                            * Output handler 0.
                                            * (Evaluate start of line.)
                                            (9EEB)
                                            OPUTHDL0 LDX RUNTRUPT ;Was a RUN interrupted?
                                            (9EEE)   BEQ NONTRUPT ;Branch if not.
 
                                            (9EF3)
                                            NONTRUPT LDX CONDNFLG ;Are we doing a warmstart ($00), coldstart ($80),
                                                                  ;using A(RAM) ($C0) or doing a READ ($01)?
                                            (9EF6)   BEQ SETIGNOR ;Branch if warmstarting.

                                            * Not doing a warmstart, so check (a) to see
                                            * if using "?" associated with READing an
                                            * INPUT statement.
                                            (9EF8)   CMP #"?"
                                            (9EFA)   BEQ OPUTHDL6 ;Branch if doing a READ.
 
                                            * Output handler 6.
                                            * (Skip the question mark prompt.)
                                            (9F71)
                                            OPUTHDL6 LDA #0       ;RESET TO CONDITION 0.
                                                     STA OPUTCOND
                                            (9F76)   BEQ DSPLYINP ;ALWAYS - go conditionally display input.

                                            (9F9D)
                                            DSPLYINP LDA #%00100000 ;Set bit pos'n 5 for test.
                                            DSPLYCHR AND CIOCUMUL ;Check if "MON I" is in effect.
                                            (9FA2)   BEQ DOSEXIT  ;Branch if display of input NOT required.

                                            * Display the char.
                                            (9FA4)
                                            DSPLYALL JSR RESTOREG

                                                                  * Restore (a), (y) & (x) registers.
                                                                  (9FBA)
                                                                  RESTOREG LDA ASAVED
                                                                           LDY YSAVED
                                                                           LDX XSAVED
                                                                           SEC          ;Why???
                                                                  (9FC4)   RTS

                                            (9FA7)   JSR GODSPLY

                                                                  (9FC5)
                                                                  GODSPLY  JMP (CSW)
                                                                           ---------

                                                                  (FDF0)
                                                                  COUT1    .
                                                                           .
                                                                  PRINT "?" CHAR THRU TRUE OUTPUT HANDLER.
                                                                  (See dis'mbly in APPLE II REFERENCE MANUAL.)
                                                                           .
                                                                           .
                                                                           (RTS)

                                            (9FAA)   STA ASAVED   ;Save (a), (y) & (x) registers.
                                                     STY YSAVED
                                            (9FB0)   STX XSAVED

                                            * Routine to exit DOS.
                                            (9FB3)
                                            DOSEXIT  JSR INITIOHK ;Reset DOS hooks.

                                                                  * Initialize the I/O hooks so that DOS intercepts
                                                                  * all input and output.   For instance, if a routine
                                                                  * encounters a "COUT  JMP (CSW)", then execution will
                                                                  * actually flow to DOS's output routine (OPUTINCP,
                                                                  * $9EBD).  Similarly, any routine that refers to
                                                                  * "RDKEY  JMP (KSW)" will actually jump to DOS's
                                                                  * input routine (INPTINCP, $9E81).
                                                                  *
                                                                  * The true (ie. normal) hooks are saved, ex:
                                                                  *   KSW: KEYIN --> KSWTRUE: KEYIN.
                                                                  *   CSW: COUT1 --> CSWTRUE: COUT1.
                                                                  * The intercepts are then set as follows:
                                                                  *   ADINPTCP: INPTINCP --> KSW: INPTINCP.
                                                                  *   ADOPUTCP: OPUTINCP --> CSW: OPUTINCP.

                                                                  * Check if input hook needs to be reset.
                                                                  (A851)
                                                                  INITIOHK LDA KSW+1
                                                                           CMP ADINPTCP+1
                                                                  (A856)   BEQ CKOUTHK  ;Input hook already points to DOS'S
                                                                                        ;input handler, so go check output hook.

                                                                  * Reset the input hook to point to DOS.
                                                                  (A858)   STA KSWTRUE+1 ;KSW: KEYIN --> KSWTRUE: KEYIN.
                                                                           LDA KSW
                                                                           STA KSWTRUE
                                                                           LDA ADINPTCP ;ADINPTCP: INPTINCP --> KSW: INPTINCP.
                                                                           STA KSW
                                                                           LDA ADINPTCP+1
                                                                  (A868)   STA KSW+1

                                                                  * Check if output hook needs to be reset.
                                                                  (A86A)
                                                                  CKOUTHK  LDA CSW+1
                                                                           CMP ADOPUTCP+1
                                                                  (A86F)   BEQ SETHKRTN ;Output hook already points to DOS's
                                                                                        ;output handler, so go exit.

                                                                  * Reset the output hook to point to DOS.
                                                                  (A871)   STA CSWTRUE+1 ;CSW: COUT1 --> CSWTRUE: COUT1.
                                                                           LDA CSW
                                                                           STA CSWTRUE
                                                                           LDA ADOPUTCP ;ADOPUTCP: OPUTINCP --> CSW: OPUTINCP.
                                                                           STA CSW
                                                                           LDA ADOPUTCP+1
                                                                           STA CSW+1
                                                                  SETHKRTN RTS
                                                                  (A883)

                                            (9FB6)   LDX STKSAVED ;Retrieve the saved stack pointer value and
                                                     TXS          ;reset the stack to return to caller.
                                            RESTOREG LDA ASAVED   ;Restore (a), (y) & (x) registers.
                                                     LDY YSAVED
                                                     LDX XSAVED
                                                     SEC          ;Return to the routine that called the routine
                                            (9FC4)   RTS          ;that contined the "JSR PREP4DOS" instruction.

                      (DB67)   AND #$7F     ;Convert char back to positive ASCII.
                               PHA          ;Save it on the stack.
                               LDA SPEEDFLG ;Delay in accordance with speed setting.
                      (DB6C)   JSR WAIT

                                            * Monitor ROM's main delay routine.
                                            * Delay z number of cycles based on
                                            * the formula:
                                            * z = ((5 *a^2) + (27 * a) + 26) / 2
                                            * where a = value in accumulator on entry.
                                            (FCA8)
                                            WAIT     SEC          ;Prepare for subtraction.
                                            WAIT2    PHA          ;Save (a) on stack.
                                            WAIT3    SBC #1       ;Keep on reducing (a) until it equals 0.
                                                     BNE WAIT3
                                                     PLA          ;Retrieve original (a) from stack.
                                                     SBC #1       ;Reduce the original (a) down to 0 again.
                                                     BNE WAIT2
                                            (FCB3)   RTS

                      (DB6F)   PLA          ;Get saved char back from stack.
                      (DB70)   RTS

(DBC7)
CKDIFRD  JSR ERRDIR

                      * Check if in deferred or immediate mode
                      * (Remember, INPUT is only applicable to
                      * deferred mode.)
                      (E306)
                      ERRDIR   LDX CURLIN+1 ;Contains #$FF if in immediate mode.
                               INX          ;If $FF ==> $00 then immediate.
                      (E309)   BNE WASDEF   ;Branch if deferred mode.
                               ----------
                               .
                               .
                               - Issue not-direct-command message.
                               ============

                      WASDEF   RTS
                      (E2AC)   ============

(DBCA)   LDA #$2C     ;Throw a $2C on the bottom of the stack
         STA BUF200-1 ;for some unknown reason????
(DBCF)   JSR INLIN

                      * INPUT A LINE OF TEXT FROM THE CURRENT INPUT DEVICE.
                      (D52C)
                      INLIN    LDX #$80     ;Designate a NULL prompt.
                      INLINPL2 STX PROMPT
                      (D530)   JSR GETLN

                                            * Get a line of input.
                                            (FD6A)
                                            GETLN    LDA PROMPT   ;PRINT NULL PROMPT.
                                            (FD6C)   JSR COUT

                                                                  * Go through the motions of printing,
                                                                  * but don't actually print anything.
                                                                  * (Using a NULL prompt.)
                                                                  (FDED)
                                                                  COUT     JMP (CSW)    ;Output hook pts to DOS's output handler.
                                                                           ------------

                                                                  * DOS's output intercept routine.
                                                                  (9EBD)
                                                                  OPUTINCP JSR PREP4DOS

                                                                                        (9ED1)
                                                                                        PREP4DOS STA ASAVED   ;Save (a), (y), & (x)
                                                                                                 STX XSAVED   ;registers.
                                                                                                 STY YSAVED
                                                                                                 TSX          ;Adjust stk ptr and
                                                                                                 INX          ;save it so that
                                                                                                 INX          ;when we later
                                                                                        (9EDD)   STX STKSAVED ;restore it and hit
                                                                                                              ;an "RTS", we can
                                                                                                              ;return to routine
                                                                                                              ;that called the
                                                                                                              ;routine that
                                                                                                              ;contained the
                                                                                                              ;"JSR PREP4DOS"
                                                                                                              ;instruction.
                                                                                                              ;(In this case,
                                                                                                              ;set to return
                                                                                                              ;to $FD6F.)

                                                                                        * Restore the I/O hooks to point to the
                                                                                        * true I/O handlers, ex:
                                                                                        *    KSWTRUE: KEYIN --> KSW: KEYIN.
                                                                                        *    CSWTRUE: COUT1 --> CSW: COUT1.
                                                                                        (9EE0)
                                                                                        UNCONDOS LDX #3
                                                                                        SETRUHKS LDA CSWTRUE,X
                                                                                                 STA CSW,X
                                                                                                 DEX
                                                                                                 BPL SETRUHKS ;4 bytes to move
                                                                                        (9EEA)   RTS          ;(0 to 3).

                                                                  * Use current OPUTCOND value to index table containing
                                                                  * address of output condition handlers.  Do a "stack jump"
                                                                  * to the appropriate condition handler entry point.
                                                                  (9EC0)   LDA OPUTCOND
                                                                           ASL          ;Times 2 cause 2 bytes per address.
                                                                           TAX          ;Set (x) to index table of addresses.
                                                                           LDA OUTHNDTB+1,X ;Put adr of output handler on stack
                                                                           PHA          ;(hi byte first) and then do a "stack jump"
                                                                           LDA OUTHNDTB,X ;to the appropriate entry point.
                                                                           PHA
                                                                           LDA ASAVED   ;Get char to be printed.
                                                                  (9ED0)   RTS          ;Execute the "stack jump"

                                                                           .
                                                                           .
                                                                  STACK JUMP TO OPUTHDL0
                                                                           .
                                                                           .
                                                                  * Output handler 0.
                                                                  * (Evaluate start of line.)
                                                                  (9EEB)
                                                                  OPUTHDL0 LDX RUNTRUPT ;Was a RUN interrupted?
                                                                  (9EEE)   BEQ NONTRUPT ;Branch if not.
 
                                                                  (9EF3)
                                                                  NONTRUPT LDX CONDNFLG ;Are we doing a warmstart ($00),
                                                                                        ;coldstart ($80), using A(RAM) ($C0)
                                                                                        ;or doing a READ ($01)?
                                                                  (9EF6)   BEQ SETIGNOR ;Branch if warmstarting.

                                                                  * Not doing a warmstart, so check (a) to see
                                                                  * if using "?" associated with READing an
                                                                  * INPUT statement.
                                                                  (9EF8)   CMP #"?"
                                                                  (9EFA)   BEQ OPUTHDL6 ;Branch if getting ready
                                                                                        ;to read a text file byte.
                                                                  (9EFC)   CMP PROMPT   ;Are we printing a prompt?
                                                                  (9EFE)   BEQ SET2EVAL ;Branch if about to print prompt.

                                                                  (9F27)
                                                                  SET2EVAL LDX #0       ;Set condition 0 - evaluate start of line.
                                                                           STX OPUTCOND
                                                                  (9F2C)   JMP DSPLYALL ;Go display char.
                                                                           ------------

                                                                  * Display the char.
                                                                  (9FA4)
                                                                  DSPLYALL JSR RESTOREG

                                                                                        * Restore (a), (y) & (x) registers.
                                                                                        (9FBA)
                                                                                        RESTOREG LDA ASAVED
                                                                                                 LDY YSAVED
                                                                                                 LDX XSAVED
                                                                                                 SEC          ;Why???
                                                                                        (9FC4)   RTS

                                                                  (9FA7)   JSR GODSPLY

                                                                                        (9FC5)
                                                                                        GODSPLY  JMP (CSW)    ;Pts to true hks.
                                                                                                 ------------

                                                                                        (FDF0)
                                                                                        COUT1    .
                                                                                                 .
                                                                                        - print char thru true output handler.
                                                                                        - ACTUALLY DOESN'T PRINT ANYTHING CAUSE
                                                                                          CHAR IS A NULL CHARACTER ($80).
                                                                                        (See dis'mbly in APPLE II REFERENCE MANUAL.)
                                                                                                 .
                                                                                                 .
                                                                                                 (RTS)

                                                                  (9FAA)   STA ASAVED   ;Save (a), (y) & (x) registers.
                                                                           STY YSAVED
                                                                  (9FB9)   STX XSAVED

                                                                  * Routine to exit DOS.
                                                                  (9FB3)
                                                                  DOSEXIT  JSR INITIOHK ;Initialize the I/O hooks so that DOS
                                                                                        ;intercepts all input & output.
                                                                                        ;(See dis'mbly above.)
                                                                  (9FB6)   LDX STKSAVED ;Retrieve the saved stack pointer val and
                                                                           TXS          ;reset the stack to return to caller.
                                                                  RESTOREG LDA ASAVED   ;Restore (a), (y) & (x) registers.
                                                                           LDY YSAVED
                                                                           LDX XSAVED
                                                                           SEC          ;Return to the routine that called the
                                                                  (9FC4)   RTS          ;routine that contained the "JSR PREP4DOS"
                                                                                        ;instruction.

                                            * Get a single byte of input.
                                            (FD6F)   LDX #1
                                            BCKSPC   TXA          ;Force fall thru to next instruction.
                                                     BEQ GETLNZ
                                                     DEX          ;Initialize (x) = 0 as index to input buf.
                                            NXTCHAR  JSR RDCHAR
                                            (FD75)

                                                                  * Routine to read an input byte.
                                                                  (FD35)
                                                                  RDCHAR   JSR RDKEY

                                                                                        (FDC0)
                                                                                        RDKEY    LDY CH       ;Get horiz cursor
                                                                                                              ;pos'n 4 nxt char.
                                                                                        (FD0E)   LDA (BASL),Y ;Pick up char in next
                                                                                        (FD10)   PHA          ;screen pos'n & save
                                                                                                              ;it on the stack.
                                                                                        (FD11)   AND #$3F     ;Convert char to
                                                                                                 ORA #$40     ;flashing.
                                                                                        (FD15)   STA (BASL),Y ;Put flashing char
                                                                                                              ;on scrn to serve
                                                                                                              ;as cursor.
                                                                                        (FD17)   PLA          ;Get char back that
                                                                                                              ;cursor is replacing.
                                                                                                              ;(Need it in case do
                                                                                                              ;bkspc or -> and
                                                                                                              ;want to reinstate
                                                                                                              ;orig char on scrn.)
                                                                                        (FD18)   JMP (CSW)    ;Input hook still
                                                                                                 -----------  ;pointing to DOS.

                                                                                        (9E81)
                                                                                        INPTINCP JSR PREP4DOS ;Save regs & stk ptr
                                                                                                              ;(In this case, set
                                                                                                              ;saved stk ptr to
                                                                                                              ;return to $FD38.)
                                                                                                              ;Pt hks at true
                                                                                                              ;I/O handlers. (See
                                                                                                              ;dis'mbly above.)
                                                                                        (9E84)   LDA CONDNFLG ;Test if doing
                                                                                        (9E87)   BEQ INPUTWRM ;warmstart.
                                                                                                              ;Fall thru if
                                                                                                              ;reading.
                                                                                        (9E89)   PHA          ;Save condition flag.
                                                                                                 LDA ASAVED   ;Put substitute
                                                                                                 STA (BASL),Y ;cursor back on scrn.
                                                                                                 PLA          ;Get condition val.
                                                                                                 BMI INPUTCLD ;Branch 4 coldstart.
                                                                                        (9E92)   JMP READTEXT ;Read file byte.
                                                                                                 ------------

                                                                                        * Routine to read a data byte.
                                                                                        (A626)
                                                                                        READTEXT JSR CKBSCRUN
                                                                                                              .
                                                                                                              .
                                                                  .............................................
                                                                  .        * Check if basic is running a program.
                                                                  .        * Exit with (x) = 1 if in immediate mode.
                                                                  .        (A65E)
                                                                  .        CKBSCRUN PHA
                                                                  .                 LDA ACTBSFLG ;Which basic is up?
                                                                  .        (A662)   BEQ INTBASIC ;Branch if using Integer.
                                                                  .
                                                                  .        * Using Applesoft - now if line
                                                                  .        * number > 65288 ($FF in hi byte),
                                                                  .        * then using immediate mode.
                                                                  .        (A664)   LDX CURLIN+1 ;Check hi byte of line #.
                                                                  .        (A666)   INX          ;(If $FF --> $00, then
                                                                  .                              ;number > 65288.)
                                                                  .        (A667)   BEQ IMEDMODE ;Branch if using immed mode.
                                                                  .
                                                                  .        * FP appears to be running a prgm
                                                                  .        * but maybe CURLIN+1 was zapped,
                                                                  .        * so also check prompt.
                                                                  .        (A669)   LDX PROMPT
                                                                  .                 CPX #$DD     ;Using an Applesoft prompt?
                                                                  .                 BEQ IMEDMODE ;Yes - must be in immed mode.
                                                                  .        RUNNING  PLA          ;Get saved char back from stk.
                                                                  .                 CLC          ;Signal program is running.
                                                                  .        (A671)   RTS
                                                                  .                 ============
                                                                  .
                                                                  .        (A672)
                                                                  .        INTBASIC LDA RUNMODE  ;Check Integer's run mode flag.
                                                                  .                 BMI RUNNING  ;If neg, Integer basic in deferred.
                                                                  .        IMEDMODE PLA          ;Get saved (a) back from stack.
                                                                  .                 SEC          ;Signal in immediate mode.
                                                                  .        (A678)   RTS
                                                                  .                 ============
                                                                  .
                                                                  .............................................
                                                                                                              .
                                                                                                              .
                                                                                        (A629)   BCS CLOSZERO ;Basic not running,
                                                                                                              ;so go close file.
                                                                                                              ;Reset to condition
                                                                                                              ;0 & do a warmstart.
                                                                                                              ;(Remeber, READ cmd
                                                                                                              ;is restricted to
                                                                                                              ;deferred mode.)
                                                                                                              ;See linear dis'mbly
                                                                                        (A62B)   LDA #6       ;SET CONDITION 6 to
                                                                                        (A62D                 ;ignore input prompt.
                                                                                        SETCOND  STA OPUTCOND
                                                                                        (A630)   JSR RDTXTBYT ;Go read text file
                                                                                                              ;data byte.

                                                                                                              * Set FM parm list
                                                                                                              * to read 1 byte
                                                                                                              * subfunction.
                                                                                                              (A68C)
                                                                                                              RDTXTBYT LDA #3
                                                                                                                       STA OPCODEFM
                                                                                                                       LDA #1
                                                                                                              (A693)   STA SUBCODFM

                                                                  
                                                                                                              * Use FM driver to
                                                                                                              * read a file byte.
                                                                                                              (A696)   JSR FMDRIVER
                                                                                                              - use read function
                                                                                                                & read-one-byte
                                                                                                                subfunction.
                                                                                                              (A699)   LDA ONEIOBUF
                                                                                                              - (a) = byte just
                                                                                                                      read.
                                                                                                              (A69C)   RTS

                                                                                        (A633) BNE NOTEND     ;If byte read < > 0,
                                                                                                              ;then haven't hit
                                                                                                              ;end-of-file marker
                                                                                                              ;yet.

                                                                                        * Ran out of data.  Picked up a $00
                                                                                        * byte either in partially full data
                                                                                        * sector or else a zeroed-out T/S
                                                                                        * link or zeroed-out data pair in
                                                                                        * T/S list sector.
                                                                                        (A636)   JSR CLOSEONE ;Go close file.
                                                                                                              ;(See dis'mbly given
                                                                                                              ;with close cmd.)
                                                                                        (A638)   LDA #3       ;Using condition 3?
                                                                                        (A63A)   CMP OPUTCOND ;Handling input
                                                                                                              ;statement?
                                                                                        (A63D)   BEQ DONEPOSN ;Yes - go to an "RTS"
                                                                                                              ;(At this point in
                                                                                        (A63F)                ;time, fall thru.)
                                                                                        ENDATERR LDA #5       ;Out of data error.
                                                                                        (A641)   JMP ERRHNDLR ;Go handle error.
                                                                                                 ------------ ;(See dis'mbly
                                                                                                              ;of errors.)

                                                                                        (A644)
                                                                                        NOTEND   CMP #$E0     ;Lowercase?
                                                                                                 BCC SAVIT    ;Branch if uppercase.
                                                                                        (A648)   AND #$7F     ;Convert lower to
                                                                                                              ;upper in order to
                                                                                                              ;fool the CAPTST
                                                                                                              ;routine in
                                                                                        (A64A)                ;monitor ROM.
                                                                                        SAVIT    STA ASAVED   ;Save char read.
                                                                                        (A64D)   LDX XSAVED   ;Get index to input
                                                                                                              ;buffer.
                                                                                        (A650)   BEQ TOEXIT   ;Branch if 1rst char.
                                                                                        (A652)   DEX          ;Turn hi bit on in
                                                                                                              ;previous char
                                                                                        (A653)   LDA BUF200,X ;stored in BUF200
                                                                                                 ORA #$80     ;to convert to
                                                                                        (A658)   STA BUF200,X ;lowercase if
                                                                                                              ;necessary.
                                                                                        TOEXIT   JMP DOSEXIT  ;Go to DOS's
                                                                                        (A65B)   ------------ ;exit routine.

                                                                                        * Routine to exit DOS.
                                                                                        (9FB3)
                                                                                        DOSEXIT  JSR INITIOHK ;Initialize the I/O
                                                                                                              ;hooks so that DOS
                                                                                                              ;intercepts all input
                                                                                                              ;& output.  (See
                                                                                                              ;dis'mbly given
                                                                                                              ;elsewhere in
                                                                                                              ;this listing.)
                                                                                        (9FB6)   LDX STKSAVED ;Reset stk pointer.
                                                                                                 TXS
                                                                                        RESTOREG LDA ASAVED   ;Restore regs.
                                                                                                 LDY YSAVED
                                                                                                 LDX XSAVED
                                                                                                 SEC          ;Return to routine
                                                                                        (9FC4)   RTS          ;that called the
                                                                                                 ============ ;routine that
                                                                                                              ;contained the
                                                                                                              ;"JSR PREP4DOS"
                                                                                                              ;instruction.

                                                                  (FD38)   CMP #$9B     ;Escape key pressed?
                                                                           BEQ ESC      ;Yes - go handle ESC.
                                                                  (FD3C)   RTS

                                            (FD78)   CMP #$95     ;Ctrl-U (ie. right arrow)?
                                                     BNE CAPTST   ;No.
                                            (FD7C)   LDA (BASL),Y ;Yes - take new char out & put char that
                                                                  ;was in advanced pos'n back on screen
                                            (FD7E)                ;because we just copied over it.
                                            CAPTST   CMP #$E0     ;Lowercase?
                                                     BCC ADDINP   ;No.
                                                     AND #$DF     ;Yes - change it to a cap.
                                            ADDINPT  STA UBF200,X ;***  PUT CHAR READ FROM FILE INTO INPUT BUFFER ***
                                                     CMP #$8D     ;<rtn>?
                                                     BNE NOTCR    ;No.
                                            (FD8B)   JSR CLREOL   ;Was rtn, so clear to end of screen line.

                                                                  * Clear to end of line by printing
                                                                  * space chars (blanks) on screen.
                                                                  (FC9C)
                                                                  CLREOL   LDY CH       ;Hirizon scrn pos'n.
                                                                  CLEOLZ   LDA #" "     ;Space.
                                                                  CLEOL2   STA (BASL),Y
                                                                           INY
                                                                           CPY WNDWDTH  ;Done entire window width yet?
                                                                           BCC CLEOL2   ;No.
                                                                  (FCA7)   RTS

                                            * GO PRINT A <CR> AT TERMINATION OF INPUT.
                                            (FD8E)
                                            CROUT    LDA #$8D     ;<cr>.
                                            (FD90)   BNE COUT     ;ALWAYS.
                                            ---------------------
                                            ---------------------

                                            (FD3D)
                                            NOTCR    LDA INVFLG   ;Save current inverse flag on stack.
                                                     PHA
                                                     LDA #$FF     ;ALWAYS use normal inverse flag during input.
                                                     STA INVFLG
                                                     LDA INVFLG
                                                     LDA BUF200,X ;Get char just put in input buffer back out
                                            (FD47)   JSR COUT     ;and go print it as normal char.

                                                                  * CONDITIONALLY INPUT CHAR JUST READ.
                                                                  (FDED)
                                                                  COUT     JMP (CSW)    ;Output hook points to DOS.
                                                                           ------------

                                                                  * DOS's output intercept routine.
                                                                  (9EBD)
                                                                  OPUTINCP JSR PREP4DOS

                                                                                        * Prepare to let DOS take over.
                                                                                        *
                                                                                        * Save (a), (y) & (x) registers
                                                                                        * and save the stack pointer.
                                                                                        * (In this case, saved stk  pointer
                                                                                        * is set to rtn to $FD4A.)
                                                                                        (9ED1)
                                                                                        PREP4DOS STA ASAVED
                                                                                                 STX XSAVED
                                                                                                 STY YSAVED
                                                                                                 TSX          ;Adjust and save
                                                                                                 INX          ;the stk pointer
                                                                                                 INX          ;so that when we later
                                                                                        (9EDD)   STX STKSAVED ;reinstate stk pointer
                                                                                                              ;we can return to
                                                                                                              ;the routine that
                                                                                                              ;called the routine
                                                                                                              ;that contained the
                                                                                                              ;"JSR PREP$DOS"
                                                                                                              ;instruction.

                                                                                        * Restore the I/O hooks to point to
                                                                                        * the true I/O handlers, ex:
                                                                                        *    KSWTRUE: KEYIN --> KSW: KEYIN.
                                                                                        *    CSWTRUE: COUT1 --> CSW: COUT1.
                                                                                        (9EE0)
                                                                                        UNCONDOS LDX #3
                                                                                        SETRUHKS LDA CSWTRUE,X
                                                                                                 STA CSW,X
                                                                                                 DEX
                                                                                                 BPL SETRUHKS ;4 bytes to move
                                                                                        (9EEA)   RTS          ;(0 to 3).

                                                                  * Use current OPUTCOND value to index table containing
                                                                  * address of output condition handlers.  Do a "stack jump"
                                                                  * to the appropriate condition handler entry point.
                                                                  (9EC0)   LDA OPUTCOND
                                                                           ASL          ;Times 2 cause 2 bytes per address.
                                                                           TAX          ;(x) = index to tbl of entry pt adrs.
                                                                           LDA OUTHNDTB+1,X ;Put adr of output handler on stack
                                                                           PHA          ;(hi byte first) and then do a "stack jump"
                                                                           LDA OUTHNDTB,X ;to the appropriate entry point.
                                                                           PHA
                                                                           LDA ASAVED   ;Get char to be printed.
                                                                  (9ED0)   RTS          ;Execute the "stack jump"

                                                                           .
                                                                           .
                                                                  STACK JUMP TO OPUTHDL6
                                                                           .
                                                                           .
                                                                  * Output handler 6.
                                                                  * (Skip the question mark prompt.)
                                                                  (9F71)
                                                                  OPUTHDL6 LDA #0       ;SET CONDITION 0.
                                                                           STA OPUTCOND
                                                                  (9F76)   BEQ DSPLYINP ;ALWAYS - go display input conditionally.

                                                                  (9F9D)
                                                                  DSPLYINP LDA #%00100000 ;Set bit 5 to see if using "MON I".
                                                                  DSPLYCHR AND CIOCUMUL ;Test flag - see if should display.
                                                                  (9FA2)   BEQ DOSEXIT  ;No display - specific bit was off,.
                                                                                        ;MON/NOMON CLR/SET specific bit.

                                                                  * Display the char on the screen.
                                                                  (9FA4)
                                                                  DSPLYALL JSR RESTOREG

                                                                                        (9FBA)
                                                                                        RESTOREG LDA ASAVED   ;Restore (a), (y) &
                                                                                                 LDY YSAVED   ;(x) registers.
                                                                                                 LDX XSAVED
                                                                                                 SEC          ;Why???
                                                                                        (9FC4)   RTS

                                                                  (9FA7)   JSR GODSPLY  ;Output char via true output handler.

                                                                                        (9FC5)
                                                                                        GODSPLY  JMP (CSW)
                                                                                                 ------------

                                                                                        (FDF0)
                                                                                        COUT1    .
                                                                                                 .
                                                                                        - PRINT CHAR THAT WAS JUST READ
                                                                                          (IE., INPUT) FROM THE FILE.
                                                                                        (See dis'mbly of monitor ROM in
                                                                                        the APPLE II REFERENCE MANUAL.)
                                                                                                 .
                                                                                                 .
                                                                                                 (RTS)

                                                                  (9FAA)   STA ASAVED   ;Save (a), (y) and (x) registers.
                                                                           STY YSAVED
                                                                  (9FB0)   STX XSAVED

                                                                  * Routine to exit DOS.
                                                                  (9FB3)
                                                                  DOSEXIT  JSR INITIOHK ;Reset I/O hooks to point to DOS.
                                                                                        ;(See dis'mbly given below.)
                                                                  (9FB6)   LDX STKSAVED ;Retrieve saved stack pointer.
                                                                           TXS
                                                                  RESTOREG LDA ASAVED   ;Restore (a), (y) & (x) registers.
                                                                           LDY YSAVED
                                                                           LDX XSAVED
                                                                           SEC          ;Why???
                                                                  (9FC4)   RTS

                                            (FD4A)   PLA          ;Retrieve orig val & restore inverse flag.
                                                     STA INVFLG
                                                     LDA BUF200,X ;Retrieve char.
                                                     CMP #$88     ;Was it a back space?
                                                     BEQ BCKSPC   ;Yes - go to back-space handling routine.
                                                     CMP #$9B     ;Was it a ctrl-X (used to cancel line)?
                                                     BEQ CANCEL   ;Yes - go to cancel routine.
                                                     CPX #$FB     ;Got 249 chars yet (ie. 0 to 248)?
                                                     BCC NOTCR1   ;No.
                                                     JSR BELL     ;Yes - ring warning bell.
                                            NOTCR1   INX          ;Kick up buffer counter.
                                            (FD60)   BNE NXTCHAR  ;GO BACK FOR MORE CHARS.
                                                     .
                                                     .
                                                     ============

                                            * PRINT A <CR> AT TERMINATION OF INPUT.
                                            (FDED)
                                            COUT     JMP (CSW)    ;Output hook points at DOS.
                                                     ------------

                                            (9EBD)
                                            OPUTINCP JSR PREP4DOS

                                                                  * Prepare to let DOS process info.
                                                                  * Save (a), (y) & (x) registers
                                                                  * and save the stack pointer.
                                                                  (9ED1)
                                                                  PREP4DOS STA ASAVED
                                                                           STX XSAVED
                                                                           STY YSAVED
                                                                           TSX          ;Adjust and save stk pointer so will
                                                                           INX          ;later rtn to $D533 when stk pointer
                                                                           INX          ;is reinstated & we hit an "RTS".
                                                                  (9EDD)   STX STKSAVED

                                                                  * Restore the I/O hooks to point to
                                                                  * the true I/O handlers, ex:
                                                                  *    KSWTRUE: KEYIN --> KSW: KEYIN.
                                                                  *    CSWTRUE: COUT1 --> CSW: COUT1.
                                                                  (9EE0)
                                                                  UNCONDOS LDX #3
                                                                  SETRUHKS LDA CSWTRUE,X
                                                                           STA CSW,X
                                                                           DEX
                                                                           BPL SETRUHKS ;4 bytes to move
                                                                  (9EEA)   RTS          ;(0 to 3).

                                            * Use current OPUTCOND value to index table containing
                                            * address of output condition handlers.  Do a "stack jump"
                                            * to the appropriate condition handler entry point.
                                            (9EC0)   LDA OPUTCOND
                                                     ASL          ;Times 2 cause 2 bytes per address.
                                                     TAX          ;Set (x) to index tbl of entry point adrs.
                                                     LDA OUTHNDTB+1,X ;Put adr of output handler on stack
                                                     PHA          ;(hi byte first) and then do a "stack jump"
                                                     LDA OUTHNDTB,X ;to the appropriate entry point.
                                                     PHA
                                                     LDA ASAVED   ;Get char to be printed.
                                            (9ED0)   RTS          ;Execute the "stack jump"

                                                     .
                                                     .
                                            STACK JUMP TO OPUTHDL6
                                                     .
                                                     .
                                            * Output handler 6.
                                            * (Skip the question mark prompt.)
                                            (9F71)
                                            OPUTHDL6 LDA #0       ;SET CONDITION 0.
                                                     STA OPUTCOND
                                            (9F76)   BEQ DSPLYINP ;ALWAYS - go display input conditionally.

                                            (9F9D)
                                            DSPLYINP LDA #%00100000 ;Set bit 5 to see if using "MON I".
                                            DSPLYCHR AND CIOCUMUL ;Test flag - see if should display.
                                            (9FA2)   BEQ DOSEXIT  ;No display - specific bit was off.
                                                                  ;(MON/NOMON CLR/SET specific bit.)

                                            * Display the char on the screen.
                                            (9FA4)
                                            DSPLYALL JSR RESTOREG

                                                                  (9FBA)
                                                                  RESTOREG LDA ASAVED   ;Restore (a), (y) &
                                                                           LDY YSAVED   ;(x) registers.
                                                                           LDX XSAVED
                                                                           SEC          ;Why???
                                                                  (9FC4)   RTS

                                            (9FA7)   JSR GODSPLY  ;Output char viat ture output handler.

                                                                  (9FC5)
                                                                  GODSPLY  JMP (CSW)
                                                                           ------------

                                                                  (FDF0)
                                                                  COUT1    .
                                                                           .
                                                                  - PRINT INPUT-TERMINATING <CR>.
                                                                  (See dis'mbly of monitor ROM in
                                                                  the APPLE II REFERENCE MANUAL.)
                                                                           .
                                                                           .
                                                                           (RTS)

                                            (9FAA)   STA ASAVED   ;Save (a), (y) and (x) registers.
                                                     STY YSAVED
                                            (9FB0)   STX XSAVED

                                            * Routine to exit DOS.
                                            (9FB3)
                                            DOSEXIT  JSR INITIOHK ;Reset I/O hooks to point to DOS.

                                                                  * Initialize the I/O hooks so that DOS intercepts
                                                                  * all input and output.   For instance, if a routine
                                                                  * encounters a "COUT  JMP (CSW)", then execution will
                                                                  * actually flow to DOS's output routine (OPUTINCP,
                                                                  * $9EBD).  Similarly, any routine that refers to
                                                                  * "RDKEY  JMP (KSW)" will actually jump to DOS's
                                                                  * input routine (INPTINCP, $9E81).
                                                                  *
                                                                  * The true (ie. normal) hooks are saved, ex:
                                                                  *   KSW: KEYIN --> KSWTRUE: KEYIN.
                                                                  *   CSW: COUT1 --> CSWTRUE: COUT1.
                                                                  * The intercepts are then set as follows:
                                                                  *   ADINPTCP: INPTINCP --> KSW: INPTINCP.
                                                                  *   ADOPUTCP: OPUTINCP --> CSW: OPUTINCP.

                                                                  * Check if input hook needs to be reset.
                                                                  (A851)
                                                                  INITIOHK LDA KSW+1
                                                                           CMP ADINPTCP+1
                                                                  (A856)   BEQ CKOUTHK  ;Input hook already points to DOS'S
                                                                                        ;input handler, so go check output hook.

                                                                  * Reset the input hook to point to DOS.
                                                                  (A858)   STA KSWTRUE+1 ;KSW: KEYIN --> KSWTRUE: KEYIN.
                                                                           LDA KSW
                                                                           STA KSWTRUE
                                                                           LDA ADINPTCP ;ADINPTCP: INPTINCP --> KSW: INPTINCP.
                                                                           STA KSW
                                                                           LDA ADINPTCP+1
                                                                  (A868)   STA KSW+1

                                                                  * Check if output hook needs to be reset.
                                                                  (A86A)
                                                                  CKOUTHK  LDA CSW+1
                                                                           CMP ADOPUTCP+1
                                                                  (A86F)   BEQ SETHKRTN ;Output hook already points to DOS's
                                                                                        ;output handler, so go exit.

                                                                  * Reset the output hook to point to DOS.
                                                                  (A871)   STA CSWTRUE+1 ;CSW: COUT1 --> CSWTRUE: COUT1.
                                                                           LDA CSW
                                                                           STA CSWTRUE
                                                                           LDA ADOPUTCP ;ADOPUTCP: OPUTINCP --> CSW: OPUTINCP.
                                                                           STA CSW
                                                                           LDA ADOPUTCP+1
                                                                           STA CSW+1
                                                                  SETHKRTN RTS
                                                                  (A883)

                                            (9FB6)   LDX STKSAVED ;Restore saved stack pointer.
                                                     TXS
                                            RESTOREG LDA ASAVED   ;Restore (a), (y) & (x) registers.
                                                     LDY YSAVED
                                                     LDX XSAVED
                                                     SEC          ;Why???
                                            (9FC4)   RTS          ;Return to the routine that called
                                                                  ;the routine that contained the
                                                                  ;"JSR PREP4DOS" instruction.

                      (D533)   CPX #$EF     ;Got 239 chars yet?
                               BCC TERMIN8  ;No.
                               LDX #$EF     ;End line at 239 chars maximum.
                      TERMIN8  LDA #0       ;Put in an eol marker.
                               STA BUF200,X
                               TXA
                               BEQ NEG8NPUT
                      CNVRTPOS LDA BUF200-1,X ;Convert to positive ASCII.
                               AND #$7F
                               STA BUF200-1,X
                               DEX
                               BNE CNVRTPOS
                      NEG8NPUT LDA #0
                               LDX #<BUF200-1
                               LDY #>BUF200-1
                      (D552)   RTS

(DBD2)   .
         .
         .
- build descriptor for variable
  data read via INPUT statement.
- store variable in memory.
- pick up end-of-marker & exit to
  Applesoft caller of the INPUT routine.
         .
         .
         (RTS)