Output of C programs | Set 31 (Pointers)

Prerequisite: Pointers in C/C++

1. Question 1 What will be the output?

C

#include<stdio.h>

int main()
{
    int a[] = { 1, 2, 3, 4, 5} ;
    int *ptr;
    ptr = a;
    printf(" %d ", *( ptr + 1) );

    return 0;
}

1. output

  2

1. Description: It is possible to assign an array to a pointer. so, when ptr = a; is executed the address of element a[0] is assigned to ptr and *ptr gives the value of element a[0]. When *(ptr + n) is executed the value at the nth location in the array is accessed.
2. Question 2 What will be the output?

C

#include<stdio.h>

int main()
{
    int a = 5;
    int *ptr ;
    ptr = &a;
    *ptr = *ptr * 3;
    printf("%d", a);

    return 0;
}

1. Output:

 15

1. Description: ptr = &a; copies the address of a in ptr making *ptr = a and the statement *ptr = *ptr * 3; can be written as a = a * 3; making a as 15.
2. Question 2 What will be the output?

C

#include<stdio.h>

int main()
{
    int i = 6, *j, k;
    j = &i;
    printf("%d\n", i * *j * i + *j);
    return 0;
}

1. Output:

222
    

1. Description: According to BODMAS rule multiplication is given higher priority. In the expression i * *j * i + *j;, i * *j *i will be evaluated first and gives result 216 and then adding *j i.e., i = 6 the output becomes 222.
2. Question 4 What will be the output?

C

#include<stdio.h>

int main()
{
    int x = 20, *y, *z;

    // Assume address of x is 500 and
    // integer is 4 byte size
    y = &x;
    z = y;
    *y++;
    *z++;
    x++;
    printf("x = %d, y = %d, z = %d \n", x, y, z);
    return 0;
}

1. Output:

x=21 y=504 z=504

1. Description: In the beginning, the address of x is assigned to y and then y to z, it makes y and z similar. when the pointer variables are incremented their value is added with the size of the variable, in this case, y and z are incremented by 4.
2. Question 5 What will be the output?

C

#include<stdio.h>

int main()
{
    int x = 10;
    int *y, **z;
    y = &x;
    z = &y;
    printf("x = %d, y = %d, z = %d\n", x, *y, **z);
    return 0;
}

1. Output:

x=10 y=10 z=10

1. Description: *y is a pointer variable whereas **z is a pointer to a pointer variable. *y gives the value at the address it holds and **z searches twice i.e., it first takes the value at the address it holds and then gives the value at that address.

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