printf just before a delay doesn't work in C

Does anyone know why if i put a printf just before a delay it waits until the delay is finished before it prints de message? Code1 with sleep(): ``` int main (void) { printf ("hi world"); system("sleep 3"); } ``` Code2 with a self implemented delay: ``` void delay(float sec) { time_t start; time_t current; time(&start); do{ time(&current); }while(difftime(current,start) < sec); } int main (void) { printf ("hi world"); delay(3); } ``` And if: ``` printf ("hi world"); delay(3); printf ("hi world"); delay(3); ``` it waits until the sum of sleeps and then it prints the messages at the same time Why does this happen? UPDATE: I writed delay("sleep 3") when i called delay, i meant delay(3). Corrected