C/stdlib.h/exit
exit: causes immediate, normal termination of a program
//Declaration: void exit(int exit_code);
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
char choice;
do {
printf("Enter names (E)\n");
printf("Delete name (D)\n");
printf("Print (P)\n");
printf("Quit (Q)\n");
choice = getchar();
} while(!strchr("EDPQ", toupper(choice)));
if(choice=="Q") exit(0);
return choice;
}