Scott at 19:13, 31 January 2011

2011-01-31T19:13:31Z

New page

Reference: http://publications.gbdirect.co.uk/c_book/

==Example Program==
<source lang="c">
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char* argv[]){
printf("Enter your name: ");
char name[64] = "";
scanf("%s", name);
printf("Hi there, %s!\n", name);
}
</source>
compile with
<pre>
$ gcc test.c -o test
</pre>

==Comments==
<source lang="c">
# /* hi there
# * here is my multi-line comment
# */
</source>

==Preprocessor directives==

Include another entire file
<source lang="c">
#include <stdio.h>
</source>
Symbol replacement:
<source lang="c">
#define PI 3.1.41592
circumference = 2*PI*radius;
</source>

==Function declaration and definition==

If you want a function to be available to other files, declare its prototype in a myprogram.h file:
<source lang="c">
int make_an_int(int); /* function prototype
</source>
Define it in the myprogram.c file:
<source lang="c">
int make_an_int(int my_arg){
return my_arg + 10;
}
</source>
A function that takes no argument and returns nothing:
<source lang="c">
void do_nothing(void); /* declaration/prototype */
void do_nothing(void){} /* definition must have curly braces, no semicolon required*/
</source>
In the body of a function, all variables must be declared before any statements show up. Variable declarations may include assignment to a literal.

==The main() function==
<source lang="c">
int main(){...}
</source>
Set the return value to 0 to indicate success; set the return value to something else to specify an error.

==Strings==

Multi-line string literals:
<source lang="c">
"This would not be valid but doesn't have \
a newline in it as far as the compiler is concerned"
</source>
String literals with only white space in between are concatenated:
<source lang="c">
"All this " "comes out as "
"just one string"
</source>

C Basics - Revision history

Scott at 19:13, 31 January 2011