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-=-=-=-=-=-=-
- *****************************************************************
- *
- DOS's coldstart routine *
- *
- ----------------------------------------------------------------*
- *
- The DOS cold- and warmstart routines represent the focal *
- points from which DOS begins processing information. It *
- therefore seems logical that the novice should launch his trek *
- into DOS from these routines. However, the cold- and warm- *
- start routines are difficult to understand because: *
- 1) Program execution bounces back and forth between DOS, *
- BASIC and monitor ROM. *
- 2) Both the cold- and warmstart routines are riddled with *
- references to an obscure version of Applesoft that most *
- people don't even realize exists. *
- 3) The DOS coldstart routine uses part of the warmstart *
- routine. In order to distinguish between these two *
- execution patterns, it is important to pay close *
- attention to the condition of the status register and *
- several different flags. *
- *
- ABOUT PROGRAM EXECUTION AND THE I/O HOOKS. *
- The interconnection between DOS, BASIC and monitor ROM is *
- accomplished by DOS's control over the input (KSW: $36,$37) *
- and output (CSW; $38,$39) hooks. (These hooks are collectively*
- referred to as the I/O hooks, the KSW/CSW hooks or the *
- keyboard/character switches.) In order to understand how DOS *
- controls these hooks, lets first see what happens when DOS is *
- NOT present: *
- - Ordinarily, data output flows through a monitor ROM routine *
- called "COUT" ($FDED). COUT contains a "JMP (CSW)" instruc- *
- tion. CSW points to the address of the peripheral to which *
- output should be sent. For instance, if output is destined *
- for the screen, CSW points to a monitor routine called *
- "COUT1" ($FDF0). After COUT1 does some homework, it sends *
- the character to the screen. Similarly, input normally *
- flows through the "RDKEY" ($FD0C) routine located in monitor *
- ROM. This routine contains a "JMP (KSW)" instruction. KSW *
- normaly points to the monitor routine known as "KEYIN" *
- ($FD1D). KEYIN accepts input from the keyboard. *
- Now, let's put DOS back into the picture: *
- - When a coldstart is done, the INITIOHK ($A851) routine in *
- DOS initializes the I/O hooks to point at DOS's own input *
- (INPTINCP, $9E8A) and output (OPUTINCP, $9E8D) handlers. *
- Therefore, when DOS is up, any routine that requests input *
- or output, must go through DOS'S own I/O handlers to be *
- screened. The I/O handlers decide whether the input is to *
- be taken from the keyboard or the disk and whether output *
- should be sent to the screen, the disk, the printer or any *
- other output device. For example, let's assume that we are *
- running a BASIC program that calls for a character to be *
- printed on the screen. When BASIC's "PRINT" statement is *
- encountered, execution flows to the "JMP (CSW)" instruction *
- in the monitor at COUT ($FDED). Because the output hook *
- (CSW) points to DOS'S output handler, execution flows to *
- OPUTINCP ($9E8D). OPUTINCP looks at the command line and *
- discovers that the character is to be sent to the screen. *
- It then calls PREP4DOS ($9ED1) to repoint the output hook at *
- the true output handler (COUT1, $FDF0) and JSR's to COUT1. *
- After COUT1 puts the character on the screen, execution *
- returns to DOS. DOS does some homework and then execution *
- flows back to BASIC. Before DOS is exited however, it again *
- calls the INITIOHK routine to reset the I/O hooks to point *
- at DOS's own I/O handlers. *
- In otherwords, DOS acts like an omnipotent peeping Tom. He *
- screens all input and output and then takes whatever action he *
- deems appropriate. *
- *
- PARLEZ VOUS APPLESOFT? *
- The first three models of Apple II computers were based *
- on two different versions of ROM. Old Apples II's contained *
- Integer basic in ROM whereas the newer Apple II+/IIe's were *
- built with Applesoft basic in ROM. In order to accommodate *
- both types of machines and their hapless programmers, Apple *
- made the DOS Master disk bilingual. When you boot with this *
- disk, DOS determines what kind of machine you're using and *
- what language to load on the RAM card. For example, if you *
- are using a II+ or IIe, the system master disk automatically *
- runs the "HELLO" program. The "HELLO" program then loads a *
- file called "INTBASIC" onto the RAM card. (INTBASIC is a *
- binary file which represents an image of the Integer basic *
- language.) Similarly, if you're using an old Apple II *
- machine, the system master will run an Integer program *
- (confusingly called, "APPLESOFT") which loads a file called *
- "FPBASIC" onto the language card. (FPBASIC is a binary file *
- which represents an image of Applesoft Floating Point Basic.) *
- Because this ram-resident version of Applesoft has gone *
- through several evolutionary stages, it is referred to in the *
- literature by several different names: disk-based Applesoft, *
- Applesoft RAM, cassette Applesoft, RAM Applesoft and A(RAM). *
- Therefore, because the language card can contain a *
- different language than the motherboard, the cold- and warm- *
- start routines must determine not only which language is *
- presently active, but also if the active language is on the *
- card or motherboard. *
- *
- FLAGS AND EXECUTION PATTERNS. *
- The status register is used to distinguish between the *
- cold- and warmstart execution patterns. In some cases (ex. *
- CMWRMCLD, $9DD1), the carry flag is used to determine if a *
- cold- or warmstart is being executed. However, in other cases *
- (ex. OPUTINCP, $9E8D) and INPTINCPT, $9E81), a specific memory *
- location is used as a flag. Because several flags appear to *
- have similar connotations but are set and tested at different *
- times, one must keep close tabs on the different flag *
- conditions: *
- (AA51) *
- CONDNFLG = I/O condition flag. *
- = $00 = warmstart. *
- = $01 = reading a file. *
- = $C0 = using A(RAM). *
- (AA52) *
- OPUTCOND = character output condition flag. *
- = $00 = evaluate start of input line. *
- = $01 = got a DOS control character, so collect *
- the DOS command. *
- = $02 = not a DOS command, so just print a <cr> *
- and return to the caller. *
- = $03 = get ready to process an INPUT statement. *
- = $04 = writing data to the disk. *
- = $05 = evaluate the first char of the data line *
- read from the disk. *
- = $06 = ignore a question mark prompt & reset to *
- condition 0. *
- (AAB3) *
- EXECFLAG = non-zero value (actually first char of the *
- name of the exec file) = presently EXECing. *
- = $00 = not execing a file. *
- (AAB6) *
- ACTBSFLG = active basic flag. *
- = $00 = integer. *
- = $40 = A(ROM). *
- = $80 = A(RAM). *
- (AAB7) *
- RUNTRUPT = run intercept flag. *
- = $00 = RUN command was NOT interrupted. *
- = $40 = RUN command was interrupted to load *
- a file when using A(ROM). *
- = $80 = RUN command was interrupted to load *
- a file when using A(RAM). *
- (E000) *
- BASICCLD = BASIC's coldstart routine. *
- (First byte distinguishes type of ROM used.) *
- = $20 = opcode for "JSR", denotes Integer. *
- = $40 = opcode for "JMP", denotes A(ROM). *
- *
- To help keep things in perspective, the general features *
- of the cold- and warmstart routines are described below: *
- *
- COLDSTART - determine what language & ROM is being used *
- and fill in the active basic entry point *
- vector table accordingly. *
- - reset the I/O hooks so that DOS can intercept *
- all input & output. *
- - simulate a "NOMON" command. *
- - rebuild the DOS buffers (resetting HIMEM, *
- discarding strings and wiping out the prgm). *
- - print a prompt and wait for input. *
- WARMSTART - reset the language card to the language used *
- when DOS was last cold started. *
- - reset the I/O hooks so DOS can intercept all *
- input and output. *
- - simulate a "NOMON" command. *
- - (note that the program and variables are left *
- intact.) *
- *
- ================================================================*
- DOS's coldstart routine.
- (P.S. Don't confuse with basic's coldstart
- routine (BASICCLD, $E000).)
(9D84)
DOSCOLD LDA IBSLOT ;Slot * 16 from RWTS's IOB table.
LSR ;Divide by 16.
LSR
LSR
LSR
STA SLOTPRSD ;Put slot in parsed table.
LDA IBDRVN ;Drive # from RWTS's IOB.
(9D91) STA DRVPRSD ;Put drive in parsed table.
- Check which basic is in ROM.
(9D94) LDA BASICCLD ;Get identifying byte: $20 = integer
EOR #$20 ; $40 = A(ROM).
(9D99) BNE ISFPROM ;Branch if FP is in ROM.
(9D9B)
ISINT STA ACTBSFLG ;Set active basic flag to denote
;integer ($00).
- Copy image of INTEGER basic's entry point vector
- table to the active entry point vector table.
(9D9E) LDX #10
INT2BSIC LDA IMGINTV-1,X
STA CHAINTRY-1,X
DEX
BNE INT2BSIC
(9DA9) JMP BYPASWRM
------------
- Copy image of APPLESOFT's entry point vector
- table to the active entry point vector table.
(9DAC)
ISFPROM LDA #$40 ;Set active basic flag to #$40 to
STA ACTBSFLG ;signal using Applesoft ROM.
LDX #12
AROM2BSC LDA IMGFPV-1,X
STA CHAINTRY-1,X
DEX
BNE AROM2BSC
BYPASWRM SEC ;(c) = 1, signal for coldstart.
(9DBC) ;(c) = 0, signal for warmstart.
(9DBD) BCS CMWRMCLD ;Force branch to bypass part of the
;warmstart routine.
(9DD1)
CMWRMCLD PHP ;Save (c) denoting if warm or cold starting.
JSR INITIOHK ;Initialize the I/O hooks.
* Initialize the I/O hooks so that DOS intercepts
* all input & 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 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 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)
(9DD5) LDA #0
(9DD7) STA CIOCUMUL ;Simulate a "NOMON" command. Note that we
;can "NOP" out this instruction to defeat
;"NOMONCIO" when cold- or warmstarting.
(9DDA) STA OPUTCOND ;Set condition 0.
PLP ;Get status back off the stack.
ROR ;Use it to set CONDNFLG=$00 for warmstart
STA CONDNFLG ;or =$80 for coldstart.
(9DE2) BMI LANGCOLD ;Branch if doing coldstart.
(9DE7)
LANGCOLD JMP (TOCLDVEC) ;Jumps to BASIC's coldstart routine
------------ ;(BASICCLD) at $E000.
- NOTE: YOU ARE LEAVING THE COMFORTABLE WORLD
- OF DOS AND ENTERING THE MURKY REALM OF BASIC.
(E000)
BASICCLD JMP BSCOLDST ;Go to basic's main coldstart.
------------
- Basic's MAIN coldstart routine.
(F128)
BSCOLDST LDX #$FF ;Set hi byte of current line # to $FF to
STX CURLIN+1 ;signal immediate (direct) mode.
LDX #$FB ;RESET STACK POINTER to point to $1FB so
(F12E) TXS ;enough space is left on stack for the first
;set of link pointers & line number associated
;with an Applesoft program line.
- Set GOWARM & GOSTROUT jump vectors to point to
- coldstart, so no matter what happens, we will
- always come back to do a coldstart. (Later, once
- the coldstart is completed, the jump vectors will
- be changed.)
(F12F) LDA #<BSCOLDST
LDY #>BSCOLDST
STA GOWARM+1 ; GOWARM: JMP BSCOLDST
STA GOWARM+2
STA GOSTROUT+1 ; GOSTROUT: JMP BSCOLDST
STY GOSTROUT+2
(F13B) JSR NORMAL ;Simulate a "NORMAL" statement.
* Set the normal mode.
* (INVFLG: #$FF and FLSHMSK: #$00 for normal mode.)
(F273)
NORMAL LDA #$FF
BNE NORMINV ;ALWAYS.
INVERSE LDA #$3F
NORMINV LDX #0
SETINV STA INVFLG
STX FLSHMSK
(F27F) RTS
- Put a "JMP" opcode in GOWARM, GOSTROUT,
- JMPADRS & USR jump vectors.
(F13E) LDA #$4C ;Opcode for "JMP" instruction.
STA GOWARM
STA GOSTROUT
STA JMPADRS
(F146) STA USR
- Finish setting up the USR jump vector.
(F148) LDA #<IQERR ;Point the USR at illegal-quantity-error routine.
LDY #>IQERR
STA USR+1
(F14E) STY USR+2
- Copy the image of the CHRGET routine and
- the random number seed into page zero.
- (NOTE: There is a bug in this routine
- because it doesn't copy all of the random
- number seed. One byte is left behind!)
(F150) LDX #$1C ;BUG - should be #$1D.
MV2ZPG LDA CHRGETFP-1,X ;Get byte of orignal and copy it to
STA CHRGET-1,X ;to its zero page location.
STX SPEEDFLG ;On the last pass, set speed to 255 (SPEEDFLG=1).
DEX
(F15A) BNE MV2ZPG
- Set up more zero-page locations.
(F15C) STX TRCFLG ;Simulate a "NOTRACE" statement.
TXA
STA TEMPRY ;Contains a #$00 expect during INIT routine.
STA LASTPT+1 ;Always equals $00.
PHA ;Put a $00 on the stack at $1FB (not used).
LDA #3 ;Set the length for the temporary string
STA DSCLEN ;descriptor for use by garbage subroutines.
(F168) JSR CRDO ;Go print a <cr>.
(DAFB)
CRDO LDA #$0D ;Positive ASCII for <cr>.
(DAFD) JSR OUTDO
(DB5C)
OUTDO ORA #$80 ;Convert to neg ASCII.
CMP #" " ;Is it a ctrl char?
BCC GODOPUT ;Branch if ctrl char.
ORA FLSHMSK ;$40 for FLASH, $00 for INVERSE or NORMAL.
GODOPUT JSR COUT ;Go to output handling routine.
(DB64)
(FDED)
COUT JMP (CSW) ;DOS intercepts output via CSW hook.
------------
* DOS's output intercept routine.
(9EBD)
OPUTINCP JSR PREP4DOS
* Prepare for processing by DOS.
(9ED1)
PREP4DOS STA ASAVED ;Save (a), (y) & (x)
STX XSAVED ;registers.
STY YSAVED
TSX ;Adjust stack ptr &
INX ;save it so when we
INX ;later restore it &
(9EDD) STX STKSAVED ;then hit an "RTS"
;we will return to
;$DB67.
* Handy entry point frequently
* used by assembly language
* programmers to disconnect
* DOS completely.
(9EE0)
UNCONDOS LDX #3
SETRUHKS LDA CSWTRUE,X ;Restore the I/O
STA CSW,X ;hooks 2 pt 2 the
DEX ;true I/O handlers.
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/address.
TAX ;Set (x) to index tbl of entry pt addrs.
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.
* File not being read.
(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 warmstart, so check (a) to see
* if using "?" associated with READing an
* INPUT statement.
(9EF8) CMP #"?"
BEQ OPUTHDL6 ;Branch if doing a READ.
CMP PROMPT ;Is (a) = the prompt character?
BEQ SET2EVAL ;Branch if about to print a prompt.
SETIGNOR LDX #2 ;Set condition 2 for default to signal
STX OPUTCOND ;that non-DOS commands should be ignored.
CMP DCTRLCHR ;Is the char = DOS's control character?
(9F08) BNE OPUTHDL2 ;No.
* Output handler 2.
* (Ignore non-DOS commands.)
(9F23)
OPUTHDL2 CMP #$8D ;Is char a <rtn>?
BNE DSPLYALL ;Yes - fall thru.
SET2EVAL LDX #0 ;Set condition 0 - evaluate start
STX OPUTCOND ;of line.
(9F2C) JMP DSPLYALL ;Go display char unconditionally.
------------
* 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
* PRINT A <CR> THROUGH THE TRUE
* OUTPUT HANDLER.
(9FC5)
GODSPLY JMP (CSW)
------------
(FDF0)
COUT1 .
.
(See dis'mbly in APPLE II REFERENCE MANUAL.)
.
.
(RTS)
* Save registers.
(9FAA) STA ASAVED ;Save (a), (y) & (x) registers.
STY YSAVED
(9FB0) STX XSAVED
* Reset hooks & stack pointer.
(9FB3)
DOSEXIT JSR INITIOHK ;Reset DOS hooks.
* Initialize the I/O hooks so that DOS
* intercepts all input & output.
(A851)
INITIOHK .
.
(See dis'mbly above.)
.
.
(RTS)
* Reset stack pointer & retrieve registers.
(9FB6) LDX STKSAVED ;Retrieve the saved stack pointer value
TXS ;& reset the stack to return to caller.
RESTOREG LDA ASAVED ;Restore (a), (y) & (x) registers.
LDY YSAVED
LDX XSAVED
SEC ;Return to routine that called routine
(9FC4) RTS ;that contained "JSR PREP4DOS" instruc.
(DB67) AND #$7F ;Convert char back to positive ASCII.
PHA ;Save it on the stack.
LDA SPEEDFLG ;Delay in accordance with speed setting.
(DB6C) JSR WAIT
* Monitor ROM's main delay routine.
* Delay z number of cycles based on
* the formula:
* z = ((5 * a^2) + (27 * a) + 26) / 2
* where a = value in accumulator in entry.
(FCA8)
WAIT SEC ;Prepare for subtraction.
WAIT2 PHA ;Save (a) on the stack.
WAIT3 SBC #1 ;Keep on reducing (a)
BNE WAIT3 ;until it equals zero.
PLA ;Get original val of (a) off stack.
SBC #1 ;Reduce original (a) down to 0 again.
BNE WAIT2
(FCB3) RTS
(DB6F) PLA ;Get saved char back from stack.
(DB70) RTS
(DB00) EOR #$FF ;No reason for this?
(DB02) RTS
(F16B) .
.
- find the highest RAM location in the machine.
- put the address (plus 1) of the highest memory
location available to Applesoft in MEMSIZ ($73).
- set end of free space/top of string storage (FRETOP, $6F).
- turn off the $D6 run protection switch.
- put a $00 in $800.
- make sure that there is at least 1 page of free
space between the start of the Applesoft program
(TXTTAB, $67) and the end of free space (FRETOP, $6F).
- simulate a NEW (& CLEAR) command. (Adjusts almost
all major zero page pointers.)
- set USR vector jump ($0A - $0C).
- set GOWARM vector jump ($00 - $02).
.
.
.
(F1D2) JMP (GOWARM+1) ;Jump to basic's main command loop
------------ ;(ie. warmstart routine) called RESTART.
- BASIC'S WARMSTART ROUTINE.
- Enter with OPUTCOND = 0 and CONDNFLG = $80
- for coldstart or $00 for warmstart.
(D43C)
RESTART JSR CRDO
* Print a <cr> through basic, DOS's
* output handler (OPUTINCP) & the monior.
(DAFB)
CRDO .
.
(See dis'mbly above.)
.
.
(DB02) RTS
- Print the Applesoft prompt through
- Basic, DOS's output handler (OPUTINCP)
- and the monitor. Then, intercept input
- through DOS's input handler (INPTINCP).
(D43F) LDX #$DD ;RH brackett for Applesoft prompt.
(D441) JSR INLINPL2
(D52E)
INLINPL2 STX PROMPT
(D530) JSR GETLN
* Get a line of input.
(FD6A)
GETLN LDA PROMPT ;Print prompt.
(FD6C) JSR COUT
(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 $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/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 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 CONDITION0 - 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)
------------
* PRINT APPLESOFT PROMPT through
* the true output handler.
(FDF0)
COUT1 .
.
- print char thru true output handler.
(See dis'mbly in APPLE II REFERENCE MANUAL.)
.
.
(RTS)
* Save registers & reset hooks.
(9FAA) STA ASAVED ;Save (a), (y) & (x) registers.
STY YSAVED
(9FB0) STX XSAVED
* Routine to exit DOS.
(9FB3)
DOSEXIT JSR INITIOHK
* Initialize the I/O hooks so that DOS
* intercepts all input & output.
(A851)
INITIOHK .
.
(See dis'mbly given above.)
.
.
(RTS)
(9FB6) LDX STKSAVED ;Retrieve the saved stack pointer val
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
(FD0C)
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 (KSW) ;Input hook still
------------ ;pointing to DOS.
(9E81)
INPTINCP JSR PREP4DOS ;Save regs & stk ptr
* Adjust & save stk
* ptr so can later
* rtn to $FD38.
* Pt hks at true
* I/O handlers.
(9ED1)
PREP4DOS .
.
(See dis'mbly
above.)
.
.
(RTS)
(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.
(9E90) BMI INPUTCLD ;Branch 4 coldstart.
* Doing a coldstart.
(9E95)
INPUTCLD JSR KEYCOLD
* Initial processing
* when 1rst keyboard
* input request is
* made by basic after
* a coldstart entry.
(9DEA)
KEYCOLD .
.
.............................................
. * Test if using A(RAM) or not.
. * On entry, (a) = contents of CONDNFLG.
. * = $00 = warmstart.
. * = $01 = reading.
. * = $80 = coldstart.
. * = $C0 = using A(RAM).
. (9DEA)
. KEYCOLD ASL ;(a) * 2 to drop out hi bit.
. (9DEB) BPL SKPDARAM ;Branch if not using A(RAM).
.
. * Using A(RAM) which was loaded via
. * Integer basic (ROM).
. (9DED) STA ACTBSFLG ;Using A(RAM), set active
. ;basic flag to #$80.
.
. * Copy image of A(RAM)'s entry pt vector
. * tbl to the active entry pt vector tbl.
. (9DF0) LDX #12
. ARAM2BSC LDA IMGARAMV-1,X
. STA CHAINTRY-1,X
. DEX
. (9DF9) BNE ARAM2BSC
.
. * Blank out the primary file name buffer
. * to make sure a "HELLO" file won't be run.
. (9DFB) LDX #29 ;30 bytes to copy (0 - 29)
. BLNKPRIM LDA SCNDFNBF,X ;Copy blank secondary
. STA PRIMFNBF,X ;to primary.
. DEX
. (9E04) BPL BLNKPRIM
.
. * Build DOS buffers and set condition.
. (9E06)
. SKPDARAM LDA MAXDFLT ;Set MXFILVAL to a default
. ;value of 3.
. (9E09) STA MXFILVAL ;Note: Default value can be
. ;changed by setting MAXFDFLT
. ;between 1 and 16 & then
. ;INITing a disk.
. (9E0C) JSR BILDBUFS ;Go build the DOS buffers.
.
. (A7D4)
. BILDBUFS .
. .
. (Long routine, see dis'mbly
. given in the MAXFILES cmd.)
. .
. .
. (RTS)
.
. (9E0F) LDA EXECFLAG ;Chk if exec file actv.
. (9E12) BEQ SKPDEXEC ;Branch if not EXECing.
.
. (9E1D)
. SKPDEXEC JSR RESTAT0
.
. * Reset CONDNFLG & OPUTCOND
. * = 0 to signal file not
. * being read & set
. * condition to evaluate
. * start of line when we
. * return to OPUTINCP.
. (A75B)
. RESTAT0 LDY #0
. STY CONDNFLG
. STY OPUTCOND
. (A763) RTS
.
. * Check if the disk was just booted.
. * (If just booted disk, NDX2CMD contains a $00
. * which was etched on the disk when the disk
. * was originally booted.)
. (9E20) LDA NDX2CMD ;Was last command an "INIT"?
. (9E23) BNE OLDBOOT ;No.
.
. * Disk was just booted, so copy
. * the IMAGE of DOS's entry point
. * vector table to page 3.
. (9E25) LDX #47
. STOR3DOS LDA IMGDOSVT,X
. STA PG3DOSVT,X
. DEX
. (9E2E) BPL STOR3DOS
.
. * Program the reset key to point at
. * DOS's warmstart routine.
. *
. * Note that the reset key can be
. * programmed to point at any location
. * simply by putting the address of the
. * target routine (in low/hi format) in
. * #3F2/$3F3. Next, EOR the contents of
. * $3F3 with the number #$A5 and put the
. * result in $3F4. (If $3F3 EOR #$A5
. * is not equal to $3F4, then the disk
. * reboots and a coldstart is done.)
. (9E30) LDA IMGDOSVT+2
. STA RESETVEC+1
. EOR #$A5
. STA VLDBYTE
. LDA IMGDOSVT+1
. (9E3E) STA RESETVEC
.
. * Set the command index to RUN
. * the "HELLO" file.
. (9E41) LDA #6 ;Command index for RUN.
. ;(Can be changed to BRUN,
. ;etc.)
. (9E43) BNE DOPENDNG ;ALWAYS.
.
. * Go do the pending command. If the
. * disk was just booted, then RUN the
. * "HELLO" file. Note: The actual name
. * of the HELLO file resides in the primary
. * filename buffer. It was written to the
. * disk as part of the DOS image when the
. * disk was INITed. Therefore, if you want
. * to change the name of the HELLO file,
. * you must:
. * 1) change the file name in the
. * file name field section of
. * the appropriate directory
. * sector. (Easiest to use
. * the RENAME command.)
. * 2) zap the primary file name
. * buf on the disk (trk$01,
. * sec $09$, offsets $75 to $92.
. (9E4A)
. DOPENDNG STA NDX2CMD ;Set cmd index & go do cmd.
. (9E4D) JMP DODOSCMD
. ------------
.
. * Do the DOS command.
. (A180)
. DODOSCMD JSR RESTAT0 ;Reset condition 0.
.
. * Reset CONDNFLG & OPUTCOND
. * to 0 so signal file not
. * being read & set
. * condition to evaluate
. * start of line when we
. * return to OPUTINCP.
. (A75B)
. RESTAT0 LDY #0
. STY CONDNFLG
. STY OPUTCOND
. (A763) RTS
.
. (A183) JSR CLRFMPRM
.
. * Zero out the fm parm list.
. (A1AE)
. CLRFMPRM LDA #0
. LDY #$16
. ZFMPARM STA FMPRMLST-1,Y
. DEY
. BNE ZFMPARM
. (A1B8) RTS
.
. * Use the command index to get the
. * address (minus 1) of the command's
. * entry point. Stick the entry point
. * address on the stack (hi byte first)
. * & then do a funny jump to execute
. * the command.
. (A186) LDA NDX2CMD ;(a) = index to command.
. (A189) TAX ;(x) = index to table of
. ;entry points.
. (A18A) LDA CMDTBL+1,X ;Get addr of the cmd's
. (A18D) PHA ;routine & put it on the
. ;stack (hi byte first).
. (A18E) LDA CMDTBL,X
. PHA
. (A192) RTS ;Do a stack jump to process
. ;the command.
.
. .
. .
. (EXECUTE THE COMMAND, IE. RUN THE
. HELLO FILE WHEN COLDSTARTING.
. .
. .
. NOTE: PARTS OF THE FOLLOWING DIS'MBLY ARE
. VERY FRAGMENTED. IT IS ONLY MEANT
. TO ILLUSTRATE THE PATTERN OF PROGRAM
. FLOW. SEE DIS'MBLY OF RUN & LOAD
. COMMANDS FOR MORE DETAIL.
.
. * Run command handler.
. (A4D1)
. CMDRUN LDA ACTBSFLG ;Check which basic is
. ;current.
. ;Contains $40 if A(ROM),
. ;$80 if A(RAM), $00 if Int.
. (A4D4) BEQ LOAD4RUN ;Branch if using Integer.
. (A4D6) STA RUNTRUPT ;SET THE RUN INTERCEPT FLAG
. ;TO DENOTE THAT A RUN CMD IS
. ;BEING INTERRUPTED TO
. ;ACCOMODATE A LOAD.
. LOAD4RUN JSR CMDLOAD
.
. (A413)
. CMDLOAD .
. .
. (Load the HELLO file.)
. .
. .
. - point I/O hooks at DOS.
. .
. .
. (A44D) JMP (RLOCNTRY)
. ------------
.
. (D4F2)
. SETLINKS .
. .
. - Set up ZERO PAGE POINTERS.
. - Adjust link pointers in
. the HELLO program (so it
. is relocatable).
.............................................
.
.
.
.
............<<< S T A C K P O I N T E R W A S R E S E T >>>.................................................
.
.
.
.
(D43C)
RESTART JSR CRDO
(DAFB)
CRDO LDA #$0D ;Positive ASCII for <cr>.
(DAFD) JSR OUTDO
(DB5C)
OUTDO ORA #$80 ;Convert to neg ASCII.
CMP #" " ;Is it a ctrl char.
BCC GODOPUT ;Branch if ctrl char.
ORA FLSHMSK ;$40 for FLASH, $00 for INVERSE or NORMAL.
GODOPUT JSR COUT ;Go to output handling routine.
(DB64)
(FDED)
COUT JMP (CSW)
------------
* DOS's output intercept routine.
(9EBD)
OPUTINCP JSR PREP4DOS
* Prepare for processing by DOS.
(9ED1)
PREP4DOS STA ASAVED ;Save (a), (y) & (x)
STX XSAVED ;registers.
STY YSAVED
TSX ;Adjust stack ptr &
INX ;save it wo when we
INX ;later restore it &
(9EDD) STX STKSAVED ;then hit an "RTS"
;we will return to
;$DB67.
* Handy entry point frequently
* used by assembly language
* programmers to disconnect
* DOS completely.
(9EE0)
UNCONDOS LDX #3
SETRUHKS LDA CSWTRUE,X ;Restore the I/O
STA CSW,X ;hooks 2 pt 2 the
DEX ;true I/O handlers.
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/address.
TAX ;Set (x) to index tbl of entry pt addrs.
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?
BEQ NONTRUPT ;Branch if not.
(9EF0) JMP FINSHRUN ;Finish off the RUN command.
------------
* Finish off the RUN command because
* it was interrupted to do a LOAD.
(9F78)
FINSHRUN LDA #0 ;Zero out the run intercept flag.
STA RUNTRUPT
(9F7D) JSR INITIOHK ;Reset I/O hooks to pt at DOS.
* Initialize the I/O hooks so that DOS
* intercepts all input & output.
(A851)
INITIOHK .
.
(See dis'mbly given above.)
.
.
(RTS)
(9F80) JMP RUNFPINT ;Jump back into the RUN command
------------ ;to finish it off.
;NOTE: The stack was reset so
;we return to the correct level.
(A4DC)
RUNFPINT JSR CRVIADOS
(9FC8)
CRVIADOS LDA #$8D ;<cr>.
(9FCA) JMP GODSPLY ;Go print the <cr>.
------------
(9FC5)
GODSPLY JMP (CSW) ;AT THIS POINT IN
------------ ;TIME, DOS INTERCEPTS
;THE OUTPUT.
* DOS's output intercept routine.
(9EBD)
OPUTINCP JSR PREP4DOS
* Save registers.
* Restore the true
* I/O hooks.
* Adjust & save the
* stk ptr so can
* later rtn to $A4DF
(9ED1)
PREP4DOS STA ASAVED
STX XSAVED
STY YSAVED
TSX
INX
INX
STX STKSAVED
UNCONDOS LDX #3
SETRUHKS LDA CSWTRUE,X
STA CSW,X
DEX
BPL SETRUHKS
(9EEA) RTS
* Use current OPUTCOND value to
* index table containing the
* address of output condition
* handlers. Do a "stack jump"
* to the appropriate condition
* handler entry point.
(9EC0) LDA OPUTCOND
(9EC3) ASL ;Times 2 cause 2
;bytes/address.
(9EC4) TAX ;Set (x) to index
;tbl of entry pt
;addrs.
(9EC5) LDA OUTHNDTB+1,X ;Put adr of
PHA ;output handler on
LDA OUTHNDTB,X ;stk (hi byte 1rst)
(9ECC) PHA ;& do a "stack jump"
;to the appropriate
;entry point.
(9ECD) 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.
* RUN not interrupted.
(9EF3)
NONTRUPT LDX CONDNFLG ;Get condition.
(9EF6) BEQ SETIGNOR ;Branch for warm.
(9F00)
SETIGNOR LDX #2 ;SET CONDITION 2.
(9F02) STX OPUTCOND ;Signal ignore
;non-DOS cmds.
(9F05) CMP DCTRLCHR ;DOS's ctrl char?
(9F08) BNE OPUTHDL2 ;No.
* Output handler 2.
* (Ignore non-DOS cmds.)
(9F23)
OPUTHDL2 CMP #$8D ;<cr>?
BNE DSPLYALL ;No.
SET2EVAL LDX #0 ;SET CONDITION 0
STX OPUTCOND ;(evaluate start
(9F2C) JMP DSPLYALL ;of line).
------------
* Display the char.
(9FA4)
DSPLYALL JSR RESTOREG
* Restore registers.
(9FBA)
RESTOREG LDA ASAVED
LDY YSAVED
LDX XSAVED
SEC
(9FC4) RTS
(9FA7) JSR GODSPLY
(9FC5)
GODSPLY JMP (CSW)
-------
* PRINT A <CR> THRU
* TRUE OUTPUT HANDLER.
(FDF0)
COUT1 .
.
(See dis'mbly in APPLE
II REFERENCE MANUAL.)
.
.
(RTS)
* Save registers & reset hooks.
(9FAA) STA ASAVED
STY YSAVED
(9FB0) STX XSAVED
* Routine to exit DOS.
(9FB3)
DOSEXIT JSR INITIOHK
* Initialize I/O hks
* so DOS intercepts
* all input & output.
(A851)
INITIOHK .
.
(See dis'mbly above.)
.
.
(RTS)
(9FB6) LDX STKSAVED ;Restore stk pointer.
TXS
RESTOREG LDA ASAVED ;Restore registers.
LDY YSAVED
LDX XSAVED
SEC ;Why?????
(9FC4) RTS ;RETURN TO THE ROUTINE
;THAT CALLED THE
;ROUTINE THAT
;CONTAINED THE
;"JSR PREP4DOS"
;INSTRUCTION.
(A4DF) JSR INITIOHK
* Initialize I/O hks
* so DOS intercepts
* all input & output.
(A851)
INITIOHK .
.
(See dis'mbly above.)
.
.
(RTS)
(A4E2) JMP (RUNTRY) ;Go execute the prgm.
------------ ;(RUNTRY points to RUNFPROM if using
;A(ROM) or FPRAMRUN if using A(RAM)).
(A4FC)
RUNFPROM JSR SETZPTRS
(D665)
SETZPTRS .
.
- simulate CLEAR & RESTORE statements
- reset important zero page pointers
- REINTIALIZE THE STACK POINTER TO
POINT TO $1F8 (while retaining return
address).
.
.
(D696) RTS
.
.
............. <<< S T A C K P O I N T E R W A S R E S E T >>>.........................
.
.
(A4FF) STA PROMPT ;Zero out the prompt & on-err flag.
STA ERRFLG
(A503) JMP NEWSTT ;Jump into BASIC to execute the program.
------------
(D7D2)
NEWSTT .
.
- EXECUTES THE APPLESOFT PROGRAM.
.
.
- pops in & out of DOS whenever
a line containing a PRINT,
INPUT or GET is encountered.
.
.
BEQ RESTART
Once again the RESTART ($D43C) routine
is entered. However this time execution
flows through DOS's output (OPUTINCP, $9EBD)
and input (INPTINCP, $9E81) handlers in a manner
different than that depicted above. Because
the flags are set as shown below, the computer
eventually ends up requesting the operator to
input commands via the KEYBOARD:
CONDNFLG: $00, ACTBSFLG: $40,
RUNTRUPT: $00, and OPUTCOND: $00.
The exact execution pattern is shown in the
disassembly of the RESTART routine described
in the file titled "DOSWARMSTART".