GATE IT 2004 | Question: 61

Question

Consider the following C program:

#include <stdio.h>
typedef struct {
    char *a;
    char *b;
    } t;
void f1 (t s);
void f2 (t *p);
main()
{
    static t s = {"A", "B"};
    printf ("%s %s\n", s.a, s.b);
    f1(s);
    printf ("%s %s\n", s.a, s.b);
    f2(&s);
}
void f1 (t s)
{
    s.a = "U";
    s.b = "V";
    printf ("%s %s\n", s.a, s.b);
    return;
}
void f2(t *p)
{
    p -> a  = "V";
    p -> b = "W";
    printf("%s %s\n", p -> a, p -> b);
    return;
}

What is the output generated by the program ?

• A. $A \ B$
  $U \ V$
  $V \ W$
  $V \ W$
• B. $A \ B$
  $U \ V$
  $A \ B$
  $V \ W$
• C. $A \ B$
  $U \ V$
  $U \ V$
  $V \ W$
• D. $A \ B$
  $U \ V$
  $V \ W$
  $U \ V$

Comments

In c programming whenever we pass something using "call by value" the value of the variable is passed to a new variable of same data type(whether it is an integer, pointer or structure).

Answer 1

First print $\text{A  B}$

$\textsf{f1}$ is call by value the changes applicable only for local

from $\textsf{f1},  \text{U V}$ is printed

back in main $\text{A B}$ is printed

then in $\textsf{f2}, \text{V W}$ is printed

Hence, answer is (B).

Comments

@Arjun Sir

I am not getting any error(but you have commented, we will get an error  (see your previous comment in this section )

)

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Try using “-Wall” parameter to gcc.

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@gatecse

What is the purpose of -Wall

 (no effect here)

Answer 2

A B
U V
A B
V W