Print Characters with putchar
The check-in board needs a two-letter mark. putchar writes one character at a time; character literals use single quotes. It will not add a newline for you. This example does not call getchar, which reads from stdin.
c
#include <stdio.h>
int main(void) {
putchar('O');
putchar('K');
putchar('\n');
return 0;
}
Run it to see OK on its own line. Temporarily remove putchar('\n'); and observe that the output no longer ends with a newline.