9hello.c

/* 9hello.c */
/* http://doc.cat-v.org/plan_9/programming/c_programming_in_plan_9 */

#include <u.h>
#include <libc.h>

void main()
{
    print("hello, world\n");
    exits(0);
}

Uh... What is your question?

none
just showing this neat little piece of code

/* why.c */

#include <stdio.h>

int main()
{
    printf("Why?\n");
    return 0;
}