Question

Choose the correct option to fill?1 and?2 so that the program below prints an input string in reverse order. Assume that the input string is terminated by a newline character.
void revese (void) {
int c;
if (?1) reverse();
?2
}
main ( ) {
printf ("Enter Text"); printf("\n");
reverse ( ); printf ("\n");
}

• A. ? 1 is (getchar ( ) ! = '\n')
  ? 2 is getchar (c);
• B. ? 1 is (c = getchar ( ) ) ! = '\n')
  ? 2 is getchar (c)
• C. ? 1 is (c ! = '\n')
  ? 2 is putchar (c);
• D. ? 1 is ((c = getchar ( ) ) ! = '\n')
  ? 2 is putchar (c);

Answer 1

The correct option is D ? 1 is ((c = getchar ( ) ) ! = '\n')

? 2 is putchar (c);

• $\underset{–}{getchar\left(\right)}$ is a function which read from standard input and return integer value.
• putchar ( ) is a function which used to write a character on standard output/screen.

Here if condition need to check input is finished or not by doing ((c = getchar ( )! = '\n') i.e. when character = '\n','\n' represent end of input.
After reverse ( ) function we need to print the output by using putchar (c).