Question

After commenting Line 2 “Hello” is printed nine times but commenting Line 1 outputs “Hello” more than nine times. My question is what’s the role of ‘\n’ in this?

#include<stdio.h>
#include<stdlib.h>

int main()
{
    int tmp[10], i, n=0;

    for(i=0;i<9;i++)
    {
        tmp[i]=fork();
        if(tmp[i]>0)
            break;
        else
        {
            printf("Hello\n");  //      ---- Line 1
            printf("Hello ");   //      ---- Line 2
        }
    }
}

Answer 1

\n also flushes the standard output buffer. If it is not present, it is possible that you have previously entered data in it. Flushing also means it forces printf to print on the screen as soon as \n is processed. Otherwise it is buffered output and you can never predict how long would OS buffer your output and when precisely it chooses to actually print.