C programming quick start

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Intro

#include <stdio.h>

The #include is a "preprocessor" directive that tells the compiler to put code from the header called stdio.h into our program before actually creating the executable. stdio.h provides input output functions like printf & scanf.

int main() { }

Main body of program. Returns integer exit status to O.S. after execution. 0 = success, non zero is an error message.

hello world example

  1. include <stdio.h>

int main() {

   printf( "Hello world!\n" );
   printf( "(hit enter to end)\n" );
   getchar();
   return 0;

}

compiling with gcc

gcc hello.c -o hello

run hello world and check exit status of last command

$ ./hello
Hello world!
(hit enter to end)

$ echo $? 0 $ ./hello Hello world! (hit enter to end) ^C $ echo $? 130 <<<--- Script terminated by Control-C exit code


variables

types Char: a single character

Integer: number without decimal place

float: number with decimal place

placement

variable declarations must come before other types of statements in the given "code block"


comment syntax

/* comment text /*


if, else if , else statement

if ( TRUE ) {
   /* Execute these statements if TRUE */
}
else if ( TRUE ) {
   /* Execute these statements if TRUE */
}
else {
   /* Execute these statements if FALSE */
}