An example

/* hello.c Jeff Shallit 3/29/89 */

/* This program just print some things and quits.
* It illustrates the structure of C programs, and
* how to run the compiler
*/

#include <stdio.h>

main()
{
int n;................./* an integer variable */

....printf("Hello, world\n");
....n = 10;
....printf("The value of n is %d\n", n);
}

Comments delimited by /* and */

#include <stdio.h> reads the header (interface) file for the standard I/O
....library.
Parameters to procedures enclosed in parens, main() expects no arguments.

Every program must have a procedure called main.

Procedure body delimited by {and }.

Some special characters: \n -- newline, \t -- tab, \0 -- end of string,\f
....-- form feed.

Format specifications introduced by %, one for each additional argument to
....printf. Some useful formats: %d -- decimal integer, %s -- string,
....%c -- character, %f -- floating-point, %% -- the character % itself.