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? C Programming Series: Issue 1 ?
? Released With DNA Volume 1, Issue 2 ?
? Written by Pazuzu 04-21-1993 ?
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Welcome to Issue #1 of Pazuzu's Guide to C Programming: The Fun, Easy, And
Possibly DESTRUCTIVE Way to Learn C!
You may wonder why I'm writing an article on a non-underground topic. In
truth, it's really not any of your fucking business and you should just BUTT
OUT, MIND YOUR OWN FUCKING BUSINESS, AND ENJOY THE INFO. But, since I'm in a
good mood, I'll tell you anyway.
I've been seeing posts all over the place, on nets, local BBS's, everywhere,
with people saying "hOw Do YoU pRoGrAm In C?!^%$!$!$!!!?????". So, I decided
to write a tutorial series so that even the stupidest fool who can't even use
WINDOWS will be able to program in C, without damaging his hard drive (at
least not physically anyway.). Actually, you can't be a total idiot, you DO
have to get a C compiler, and figure out how to use it, because I'm not
telling you how to use the compiler, only how to write programs. If you can't
accomplish the simple task of getting a C compiler and figuring out how to
use it (I recommend Turbo or Borland C, as some of my examples are
TC/BC-specific), then please put your computer in a suitable shipping box and
ship it to the PO box listed at the end of this article, then place a loaded
gun to your head and pull the trigger.
C programming is not particularly difficult, and I assume only a knowledge
of either BASIC or Pascal in this series. C will save you much time when
coding, just in typing alone. For example, in Pascal, to define a code block,
you have to type "Begin" and "End". This is utterly ridiculous. In C, it is
simply "{" and "}". Besides, Pascal was invented as a teaching language
anyway, while C was made BY programmers FOR programmers, and we ALL know what
BASIC is for, so WHY would you want to use anything but C?
Variables, Declarations, Type Specifiers, Etc
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In BASIC, when you need a variable, you just use it. However, in most other
languages, you must DECLARE each variable before it is used. You do this by
telling the compiler the name of the variable and what type of data it needs
to hold. Here are a few examples in C:
int i;
register int j;
char a_string[9];
unsigned char q;
The first line declares an integer variable named "i", which can hold any
value between -32,767 and +32,767 - the maximum values allowed in 16 bits.
The second line is a special case - it tells the compiler to write code that
will use a REGISTER for the variable, if one is available. You would do this
for any variables that are used for loop control, as the CPU can access a
register MUCH faster than a memory location, and any loop control variable is
going to be accessed many times. If there is no register available, the
compiler just makes it a normal variable - you don't need to worry about it.
Line 3 is a very important example. There isn't a string data type in C - you
must use arrays of char's. Line 3 defines an 8-character string. Why only 8?,
you ask... Well, in C, every string must end in a NULL (ASCII 0), and that
NULL takes up a position in memory, so you need to always make the strings
one bigger than what you really need. The NULL is handled automagically by
all of the library's string functions.
Line 4 defines an 8-bit variable which can hold either an actual ASCII
character or an integer value in the range 0 to 255 - the maximum for 8
bits. If you define an unsigned int, you can hold a value between 0 and
65,535. The reason for this is that C assumes you want a signed unless you
say unsigned. The highest bit is always used for the sign, so with a signed
int, you can have -32,767 to +32,767 (-128 thru +128 for signed char), and
with an unsigned, you get 0 thru 65,535 for int, and 0 thru 255 for char.
There's a few other type specifiers also, the most important being long. If
you apply long to an int, you get 32 bits, which is a pretty huge range, even
if it's signed. Unsigned, it's really huge. I don't remember the range off
the top of my head, and I don't want to load the compiler and check in the
help right now, so you'll just have to figure it out yourself. But trust me,
it's big enough to handle any values you could ever possibly want.
Very Basic C Programming
~~~~~~~~~~~~~~~~~~~~~~~~
With that out of the way, on to the structure of a C program...
C is a weird language in that it defines NO, that's right - NO input/output
commands... "Well then how the fuck do I do input/output???" you ask. You do
it through FUNCTION CALLS. The C language has control structures, arithmetic
operators, and logical test commands, but no i/o commands - that is the job
of the library. Every C compiler comes with a library, and it's basically
standardized - for example, printf will almost always be printf, but the
compiler writer could have just as easily called it print_the_fucking_stuff
if he really wanted to.
A C program is made up of functions and function calls. The *MUST* be one
function, called main() which is what gets called when you first execute the
program... Here is an example of a very basic C program:
#include <stdio.h>
void main(void) {
clrscr();
printf("\n\nhElLo cReWeL, EViL, aNd WiCKED wOrLd!%$^!$!!^%$!^%$!!\n\n");
}
This illustrates several important things:
Line 1 (the #include line): The #include command isn't a C command, it's a
command to the compiler to include (I bet you would have never figured that
out!!!) another file into the compilation. In this case, we are including the
stANdARD iNPUT/oUTPUT library header file. We need to do this because without
it, the compiler won't know what the fuck we're talking about when we use any
i/o functions - they're defined in stdio.h ...
Line 2: This declares the main() function. The first void tells the compiler
that main() doesn't return any value to the caller (since there isn't one!),
while the second void tells the compiler that main() doesn't require any
parameters. The { opens the function block.
Line 3: This is a call to the library's clear screen routine.
Line 4: This prints a string. The "\n"'s are NEWLINES, they tell the function
to go to the next line. You will also notice that all statement lines and in
a ";"...
Line 5 (}): This ends main()'s function block, and also in this case the
program.
This illustrates several important points, as well as carries on the
traditional of ALWAYS making programming students write a "hello world"
program as their first. Of course, I altered the text, because I'm scum, but
ohwell.
Here is another sample program:
#include <stdio.h>
void main(void) {
register int i;
char inpstr[81];
for(i=0;i<100;i++) {
clrscr();
printf("\n\nInput a string: ");
gets(inpstr);
printf("\n\nYou typed: %s, number %i\n",inpstr,i);
gets(inpstr);
}
}
Ok, the first few lines should already be familiar for you. I'm going to
start with the "for..." line. This illustrates an important thing in C - the
for loop. Most other languages have this - in BASIC its FOR I = 1 TO 100. The
C version is a bit harder to understand, yet infinitely more powerful. The
first part ("i=0;") set the loop counter to 0. The second part ("i<100";)
specifies what condition to test when deciding if the loop is done yet. In
this case, as long as i is less than 100, the loop will execute. The last
part ("i++") specifies the increment command. This command is what gets
executed to increment the loop counter. In this case, i gets 1 added to it
every time the loop executes. The "++" operator is VERY important: In other
languages, you have to code i = i + 1 - in C, the i = i + 1 is valid -
however, it will be less efficient when compiled. The reason for the is that
the i=i+1 version compiles to an ADD instruction, while i++ would compile to
a simple INC instruction. This is far more efficient. This is called "C
SHORTHAND", and there are several others as well: i-- (subtract 1), i+=3
(i=i+3), and so on. Of course, the variable doesn't have to be i, could be
any other variable.
Another VERY important concept is demonstrated by this for loop as well - the
BLOCK STATEMENT. Any place a normal single statement is valid, a block
statement enclosed by { and } is also valid. In this example, everything
between the { and } will get executed on each iteration of the loop.
clrscr() is the Borland library function to clear the screen - other
compilers may vary.
The first printf statement should be quite obvious.
gets() is one of the Borland library functions to input a string from the
keyboard. Quite simple.
The next printf line shows off part of the true power of printf. The string
between the quotes in any printf statement is really a FORMAT STRING, and in
most cases, will just be output as is. However, if you insert any % commands,
printf will expect additional arguments to tell it what to print in their
place. The %s means put a string at this position, and %i means use an
integer. For every % command, you must have a variable, separated by commas
outside the closing quote, else you will crash your program. In this case,
printf will print "You typed: " then whatever you typed into inpstr, then ",
number " and the current value of i. This makes printf very powerful as
I'm sure you can see.
The last gets() line just makes you press enter to continue.
I've covered quite a bit here, and you can actually do quite a bit with this
small amount of knowledge, if you're creative enough. Next issue, I'll cover
pointers, bit fields, structures, and basic file accessing.
Call:
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