[Solved] not able to understand the role of getchar and putchar here

by


Look at the below code you mentioned

int main(void){
        int c;
        c = getchar();
        while (c != EOF) {
                putchar(c);

        }
        return 0;
}

When c = getchar(); executes & if you provided input as ABC at runtime & press ENTER(\n), that time c holds first character A.
Next come to loop, your condition is c!=EOF i.e A!=EOF which always true & it will print A infinitely because you are not asking second time input so c holds A.

correct version of above code is 

int main(void){
        int c;
        while ( (c = getchar())!=EOF) { /* to stop press ctrl+d */
                putchar(c);
        }
        return 0;
}

case 2 :- Now looks at second code

int main(void){
        int c;
        c = getchar(); 
        while (c != EOF) { /*condition is true */
                putchar(c);  
                c = getchar ();/*After printing ABC, it will wait for second input like DEF, unlike case-1  */ 
        }
        return 0;
}

Can anyone please explain why it is not showing just a single A as output ? Why it should prints only A, it prints whatever input you given like ABC & so on. Just note that getchar() works with buffered input i.e when you press ENTER getchar() will read upto that & when there is nothing left to read getchar() returns EOF.

solved not able to understand the role of getchar and putchar here