Programming

Question 1
Consider the following C program:
#include <stdio.h>
int counter = 0;
int calc (int a, int b) {
int c;
counter++;
if (b==3) return (a*a*a) ;
else {
c = calc (a, b/3) ;
return (c*c*c) ;
}
}
int main () {
calc (4, 81);
printf (“%d”, counter) ;
}
The output of this program is ______.
A
4
B
5
C
6
D
7
       Programming       Programming       GATE 2018       Video-Explanation
Question 1 Explanation: 
Question 2

Consider the following C program.

#include <stdio.h>
struct Outnode { 
    char x, y, z ; 
};

int main () { 
    struct Outnode p = {'1', '0', 'a'+2} ; 
    struct Outnode *q = &p ; 
    printf ("%c, %c", *((char*)q+1), *((char*)q+2)) ; 
    return 0 ; 
} 

The output of this program is

A
0, c
B
0, a+2
C
‘0’, ‘a+2’
D
‘0’, ‘c’
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Question 2 Explanation: 
char x = ‘a’+2;
The x variable here stores a character ‘c’ in it.
Because +2 will increment ascii value of a from 92 to 95.
Hence the structure p contains 3 character values and they are ‘1’, ‘0’, and ‘c’.
q is a pointer pointing to structure p.
Hence q is pointing to ‘1’, q+1 pointing to ‘0’ and q+2 pointing to ‘c’.
Option d cannot be correct, as though they are characters, printf will not print them in single quotes.
Question 3

Consider the following C program:

#include<stdio.h> 

void fun1(char *s1, char *s2)  { 
     char *tmp;  
     tmp = s1; 
     s1 = s2; 
     s2 = tmp; 
} 

void fun2(char **s2, char **s2)  { 
     char *tmp; 
     tmp = *s1; 
     *s1 = *s2; 
     *s2 = tmp; 
}

int main ()  { 
     char *str1 = "Hi", *str2 = "Bye"; 
     fun1(str1, str2);     printf("%s %s", str1, str2); 
     fun2(&str1, &str2);   printf("%s %s", str1, str2); 
     return 0; 
} 

The output of the program above is

A
Hi Bye Bye Hi
B
Hi Bye Hi Bye
C
Bye Hi Hi Bye
D
Bye Hi Bye Hi
       Programming       Programming       GATE 2018       Video-Explanation
Question 3 Explanation: 
The first call to the function ‘func1(str1, str2);’ is call by value.
Hence, any change in the formal parameters are NOT reflected in actual parameters.
Hence, str1 points at “hi” and str2 points at “bye”.
The second call to the function ‘func2(&str1, &str2);’ is call by reference.
Hence, any change in formal parameters are reflected in actual parameters.
Hence, str1 now points at “bye” and str2 points at “hi”.
Hence answer is “hi bye bye hi”.
Question 4

Consider the following C code. Assume that unsigned long int type length is 64 bits.

        unsigned long int fun(unsigned long int n)  { 
            unsigned long int i, j, j=0, sum = 0; 
            for (i = n; i > 1; i = i/2) j++; 
            for ( ; j > 1; j = j/2) sum++; 
            return sum; 
        } 

The value returned when we call fun with the input 240 is

A
4
B
5
C
6
D
40
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Question 4 Explanation: 
Since 240 is the input, so first loop will make j = 40.
Next for loop will divide j value (which is 40) by 2, each time until j>1.
j loop starts:
j=40 & sum=1
j=20 & sum=2
j=10 & sum=3
j=5 & sum=4
j=2 & sum=5
j=1 & break
So, sum = 5.
Question 5

Consider the following program written in pseudo-code. Assume that x and y are integers.

Count (x, y)  {
    if (y != 1)  {
        if (x != 1)  {
            print("*") ;
            Count (x/2, y) ;
        }
        else  {
             y = y - 1 ; 
             Count (1024, y) ; 
        }
    }
}

The number of times that the print statement is executed by the call Count(1024, 1024) is ______.

A
10230
B
10231
C
10232
D
10233
       Programming       PRogramming       GATE 2018       Video-Explanation
Question 5 Explanation: 
#include
int count=0;
Count(x,y){
if(y!=1){
if(x!=1){
printf(“*”);
count = count +1;
Count(x/2,y);
}
else{
y=y-1;
Count(1024,y);
}
}
}
void main()
{
Count(1024,1024);
printf(“\n%d\n”,count);
}


Count ( ) is called recursively for every (y = 1023) & for every y, Count ( ) is called (x = 10) times = 1023 × 10 = 10230
Question 6

Consider the following C code:

             #include <stdio.h>
             int *assignval(int *x, int val)   {
                  *x = val;
                  return x;
             }

             void main ( )  {
                  int  *x = malloc(sizeof(int));
                  if(NULL == x)  return;
                     x = assignval(x, 0);
                     if(x)  {
                           x = (int *)malloc(size of(int));
                           if(NULL == x)  return;
                              x = assignval(x, 10);
                     }
                     printf("%dn",  *x);
                     free(x);
              }

The code suffers from which one of the following problems:

A
compiler error as the return of malloc is not typecast approximately
B
compiler error because the comparison should be made as x==NULL and not as shown
C
compiles successfully but execution may result in dangling pointer
D
compiles successfully but execution may result in memory leak
       Programming       Programming       GATE 2017 [Set-1]       Video-Explanation
Question 6 Explanation: 
Option A:
In C++, we need to perform type casting, but in C Implicit type casting is done automatically, so there is no compile time error, it prints10 as output.
Option B:
NULL means address 0, if (a == 0) or (0 == a) no problem, though we can neglect this, as it prints 10.
Option C:
x points to a valid memory location. Dangling Pointer means if it points to a memory location which is freed/ deleted.
int*ptr = (int*)malloc(sizeof(int));
free(ptr); //ptr becomes a dangling pointer
ptr = NULL; //Removing Dangling pointers condition
Option D:
x is assigned to some memory location
int*x = malloc(sizeof(int));
→ (int*)malloc(sizeof(int)) again assigns some other location to x, previous memory location is lost because no new reference to that location, resulting in Memory Leak.
Hence, Option D.
Question 7

Consider the following two functions.

void fun1(int n)   {                 void fun2(int n)   {
        if(n == 0)  return;                  if(n == 0)  return;
        printf("%d", n);                     printf("%d", n);
        fun2(n - 2);                         fun1(++n);
        printf("%d", n);                     printf("%d", n);
}                                    }

The output printed when fun1(5) is called is

A
53423122233445
B
53423120112233
C
53423122132435
D
53423120213243
       Programming       Programming       GATE 2017 [Set-1]       Video-Explanation
Question 7 Explanation: 


In fun2, we increment (pre) the value of n, but in fun1, we are not modifying the value.
Hence increment in value in recursion (back).
Hence, 5 3 4 2 3 1 2 2 2 3 3 4 4 5.
Question 8

Consider the C functions foo and bar given below:

         int foo(int val)   {
                 int x = 0;
                 while (val>0)   {
                    x = x + foo(val--); 
                 }
                 return val;
               }

               int bar(int val)   {
                  int x = 0;
                  while (val>0)   {
                      x = x + bar(val-1);
                  }
                  return val;
               }

Invocations of foo(3) and bar(3) will result in:

A
Return of 6 and 6 respectively.
B
Infinite loop and abnormal termination respectively.
C
Abnormal termination and infinite loop respectively.
D
Both terminating abnormally.
       Programming       Programming       GATE 2017 [Set-1]       Video-Explanation
Question 8 Explanation: 
while(val>0)
{
x = x + foo(val–);
}
In this case foo(val–) is same as foo(val) & val– ;
Because the recursive function call is made without changing the passing argument and there is no Base condition which can stop it.
It goes on calling with the same value ‘val’ & the system will run out of memory and hits the segmentation fault or will be terminated abnormally.
The loop will not make any difference here.
while(val>0)
{
x = x + bar(val-1);
}
bar(3) calls bar(2)
bar(2) calls bar(1)
bar(1) calls bar(0) ⇾ Here bar(0) will return 0.
bar(1) calls bar(0)
bar(1) calls bar(0)……..
This will continue.
Here is a problem of infinite loop but not abrupt termination.
Some compilers will forcefully preempt the execution.
Question 9

Consider the following C program.

#include <stdio.h>
#include <string.h>

void printlength (char*s, char*t)   {
   unsigned int c = 0;
   int len = ((strlen(s) - strlen(t)) > c) ? strlen(s):strlen(t);
   printf("%d\n", len);
}

void main ()  { 
   char*x = "abc";
   char*y = "defgh";
   printlength(x,y);
}

Recall that strlen is defined in string.h as returning a value of type size_t, which is an unsigned int. The output of the program is _________.

A
3
B
4
C
5
D
6
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Question 9 Explanation: 
main ( )
{
char*x = “abc”;
char*y = “defgh”;
printlength(x,y);
}
printlength(char*3, char*t)
{
unsigned int c = 0;
int len = ((strlen(s) – strlen(t))> c) ? strlen(s) : strlen(t);
printf(“%d”, len);
}
Here strlen(s) – strlen(t) = 3 – 5 = -2
But in C programming, when we do operations with two unsigned integers, result is also unsigned. (strlen returns size_t which is unsigned in most of the systems).
So this result ‘-2’ is treated as unsigned and its value is INT_MAX-2.
Now the comparison is in between large number & another unsigned number c, which is 0.
So the comparison returns TRUE here.
Hence (strlen(s) – strlen(t))>0 will return TRUE, on executing, the conditional operator will return strlen(s)
⇒ strlen(abc) = 3
Question 10

The output of executing the following C program is __________.

           #include<stdio.h>
           int total (int v)   {
               static int count=0;
               while(v)   {
                   count += v&1;
                   v ≫= 1;
               }     
               return count;
           }

           void main()    {
               static int x = 0;
               int i = 5;
               for(; 1> 0; i--)    {
                  x = x + total(i);
               }
               printf("%d\n", x);
           }
A
23
B
24
C
25
D
26
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Question 10 Explanation: 
Arithmetic operators have least priority in this case, as count+=v & 1, we first compute v& 1 and then adds to count variable.

Question 11

Match the following:

 
A
P→(ii), Q→(iv), R→(i), S→(iii)
B
P→(ii), Q→(i), R→(iv), S→(iii)
C
P→(ii), Q→(iv), R→(iii), S→(i)
D
P→(iii), Q→(iv), R→(i), S→(ii)
       Programming       Match-the-Following       GATE 2017 [Set-2]       Video-Explanation
Question 11 Explanation: 
Static char var:
⇾ A variable located in Data Section of memory

P→(ii), Q→(iv), R→(i), S→(iii)
Question 12

Consider the following function implemented in C:

void printxy (int x, int y)   {
      int *ptr;
      x = 0;
      ptr = &x;
      y = *ptr;
      *ptr = 1;
      printf("%d,%d",x,y);
}

The output of invoking printxy(1, 1) is

A
0, 0
B
0, 1
C
1, 0
D
1, 1
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Question 12 Explanation: 
printxy (int x, int y)
{
int *ptr;
x = 0;
ptr = &x;
y = *ptr;
*ptr = 1;

}
printxy (1, 1)
Question 13

Consider the C program fragment below which is meant to divide x and y using repeated subtractions. The variables x, y, q and r are all unsigned int.

          while (r >= y)  {
              r = r - y;
              q = q + 1;
          }

Which of the following conditions on the variables x, y, q and r before the execution of the fragment will ensure that the loop terminates in a state satisfying the condition x == (y*q + r)?

A
(q == r) && (r == 0)
B
(x > 0) && (r == x) && (y > 0)
C
(q == 0) && (r == x) && (y > 0)
D
(q == 0) && (y > 0)
       Programming       Programming       GATE 2017 [Set-2]       Video-Explanation
Question 13 Explanation: 
Divide x by y.
x, y, q, r are unsigned integers.
while (r >= y)
{
r = r – y;
q = q + 1;
}
Loop terminates in a state satisfying the condition
x == (y * q + r)
y ⇒ Dividend = Divisor * Quotient + Remainder
So, to divide a number with repeated subtractions, the Quotient should be initialized to 0 and it must be incremented for every subtraction.
So initially q=0 which represents
x = 0 + r ⇒ x = r
and y must be a positive value (>0).
Question 14

Consider the following snippet of a C program. Assume that swap(&x, &y)  exchanges the contents of x and y.

int main ()  {
      int array[] = {3, 5, 1, 4, 6, 2};
      int done = 0;
      int i;

      while (done == 0)  {
           done = 1;
           for (i=0; i<=4; i++)  {
                if (array[i] < array[i+1])  {
                       swap (&array[i], &array[i+1]);
                       done = 0;
                }
           }
           for (i=5; i>=1; i--)  {
                if (array[i] > array[i-1])   {
                      swap(&array[i], &array[i-1]);
                      done=0;
                }
           }
       }
       printf("%d", array[3]);
}

The output of the program is ___________.

A
3
B
4
C
5
D
6
       Programming       Programming       GATE 2017 [Set-2]       Video-Explanation
Question 14 Explanation: 
Swap (&x, &y) exchanges the contents of x & y.

(1) ⇒ 1st for i = 0 <= 4
a[0] < a[1] ≃ 3<5 so perform swapping
done =

(1) ⇒ no swap (3, 1)
(2) ⇾ perform swap (1, 4)

(1) ⇒ perform swap (1, 6)

(1) ⇒ perform swap (1, 2)

(1) ⇒ (done is still 0)
for i = 5 >= 1 a[5] > a[4] ≃ 1>2 – false. So, no swapping to be done
(2) ⇾ no swap (6, 2)
(3) ⇾ swap (4, 6)

(1) ⇒ Swap (3, 6)

(1) ⇒ Swap (5, 6)

⇒ Done is still 0. So while loop executes again.
(1) ⇾ no swap (6, 5)
done = 1
(2) ⇾ No swap (5, 3)
(3) ⇾Swap (3, 4)

So, array [3] = 3
Question 15

Consider the following C program:

#include <stdio.h>
int main()
{
    int m = 10;
    int n, n1;
    n = ++m;
    n1 = m++;
    n--;
    --n1;
    n -= n1;
    printf("%d",n);
    return 0;
}

The output of the program is _______.

A
0
B
1
C
2
D
3
       Programming       C-Programming       GATE 2017 [Set-2]       Video-Explanation
Question 15 Explanation: 
Question 16

Consider the following C program.

#include<stdio.h>
#include<string.h>
int main ()  {
  char* c = "GATECSIT2017";
  char* p = c;
  printf("%d", (int) strlen (c + 2[p] - 6[p] - 1));
  return 0;
}

The output of the program is __________.

A
1
B
2
C
4
D
6
       Programming       Programming       GATE 2017 [Set-2]       Video-Explanation
Question 16 Explanation: 
char * C = “GATECSIT2017”;
char * P = C;
(int) strlen (C + 2[P] – 6[P] – 1)

C + 2[P] – 6[P] – 1
     ∵2[P] ≃ P[2]
100 + P[2] – P[6] – 1
100 + T – I – 1
100 + 84 – 73 – 1
     ASCII values: T – 84, I – 73
100 + 11 – 1
= 110
(int) strlen (110)
strlen (17) ≃ 2
Question 17

Consider the following C program.

void f(int, short);
void main ()
{
     int i = 100;
     short s = 12;
     short *p = &s;
     __________ ;         // call to f()
}

Which one of the following expressions, when placed in the blank above, will NOT result in a type checking error?

A
f(s, *s)
B
i = f(i, s)
C
f(i, *s)
D
f(i, *p)
       Programming       Programming       GATE 2016 [Set-1]       Video-Explanation
Question 17 Explanation: 
int i = 100;
short s = 12;
short *p = &s;
_______ // call to f ( ) :: (void f(int,short);)
It is clearly mentioned the return type of f is void.
By doing option elimination
(A) & (C) can be eliminated as s is short variable and not a pointer variable.
(B) i = f(i, s) is false because f’s return type is void, but here shown as int.
(D) f(i, *p)
i = 100
*p = 12
Hence TRUE
Question 18

Consider the following C program.

#include<stdio.h>
void mystery(int *ptra, int *ptrb) {
      int *temp;
      temp = ptrb;
      ptrb = ptra;
      ptra = temp;
}
int main() {
      int a=2016, b=0, c=4, d=42;
      mystery(&a, &b);
      if (a < c)
             mystery(&c, &a);
      mystery(&a, &d);
      printf("%d\n", a);
}

The output of the program is ________.

A
2016
B
2017
C
2018
D
2019
       Programming       Programming       GATE 2016 [Set-1]       Video-Explanation
Question 18 Explanation: 

For the first mystery (&a, &b);

temp = ptr b
ptr b = ptr a
ptr a = temp
If (a The function mystery (int *ptra, int *ptrb) does not change the value of variables pointed by pointers, instead it only changes the addresses inside the pointers, which is in no way going to modify the values of a, b, c, d.
Hence, a = 2016 will be printed.
Question 19

The following function computes the maximum value contained in an integer array p[] of size n (n >= 1).

       int max(int *p, int n) {
           int a=0, b=n-1;
           
           while (__________) {
               if (p[a] <= p[b]) {a = a+1;}
               else                 {b = b-1;}
           }

           return p[a];
       }

The missing loop condition is

A
a != n
B
b != 0
C
b > (a + 1)
D
b != a
       Programming       Programming       GATE 2016 [Set-1]       Video-Explanation
Question 19 Explanation: 
main ( )
{
int arr [ ] = {3, 2, 1, 5, 4};
int n = sizeof(arr) / sizeof (arr[0]);
printf (max(arr, 5));
}
int max (int *p, int n)
{
int a = 0, b = n – 1;
(while (a!=b))
{
if (p[a] <= p[b])
{
a = a + 1;
}
else
{
b =b – 1;
}
}
return p[a];
}
The function computes the maximum value contained in an integer array p[ ] of size n (n >= 1).
If a = = b, means both are at same location & comparison ends.
Question 20

What will be the output of the following C program?

void count(int n)  {
     static int d=1;

     printf("%d ", n);
     printf("%d ", d);
     d++;
     if(n>1) count(n-1);
     printf("%d ", d);
}

void main() {
     count(3);
}
A
3 1 2 2 1 3 4 4 4
B
3 1 2 1 1 1 2 2 2
C
3 1 2 2 1 3 4
D
3 1 2 1 1 1 2
       Programming       Programming       GATE 2016 [Set-1]       Video-Explanation
Question 20 Explanation: 

Count (3)
static int d = 1
It prints 3, 1
d++; //d = 2
n>1, count(2)
prints 2, 2
d++; // d = 3
n>1, count(1)
prints 1, 3 → Here n = 1, so condition failed & printf (last statement) executes thrice & prints d
d++; //d=4 value as 4. For three function calls, static value retains.
∴ 312213444
Question 21

What will be the output of the following pseudo-code when parameters are passed by reference and dynamic scoping is assumed?

       a=3;
       void n(x) {x = x * a; print(x);}
       void m(y) {a = 1; a = y - a; n(a); print(a);}
       void main() {m(a);}
A
6, 2
B
6, 6
C
4, 2
D
4, 4
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Question 21 Explanation: 

First m(a) is implemented, as there are no local variables in main ( ), it takes global a = 3;
m(3) is passed to m(y).
a = 1
a = 3 – 1 = 2
n(2) is passed to n(x).
Since it is dynamic scoping
x = 2 * 2 = 4 (a takes the value of its calling function not the global one).
The local x is now replaced in m(y) also.
Hence, it prints 4,4.
And we know it prints 6, 2 if static scoping is used.
It is by default in C programming.
Question 22

The value printed by the following program is __________.

     void f(int* p, int m) {
        m = m + 5;
        *p = *p + m;
        return;
     }

     void main() {
        int i=5, j=10;
        f(&i, j);
        printf("%d", i+j);
     }
A
30
B
31
C
32
D
33
       Programming       Programming       GATE 2016 [Set-2]       Video-Explanation
Question 22 Explanation: 

P is a pointer stores the address of i, & m is the formal parameter of j.
Now, m = m + 5;
*p = *p + m;

Hence, i + j will be 20 + 10 = 30.
Question 23

The following function computes XY for positive integers X and Y.

       int exp (int X, int Y) {
           int res = 1, a = X, b = Y;

           while ( b != 0 ){
               if ( b%2 == 0) { a = a*a; b = b/2; }
               else           { res = res*a; b = b-1; }
           }
           return res;

        }

Which one of the following conditions is TRUE before every iteration of the loop?

A
XY = ab
B
(res * a)Y = (res * X)b
C
XY = res * ab
D
XY = (res * a)b
       Programming       Programming       GATE 2016 [Set-2]       Video-Explanation
Question 23 Explanation: 
int exp (int X, int Y)
{
int res = 1, a = X, b = Y;
while (b != 0)
{
if (b%2 == 0)
{
a = a*a;
b = b/2;
}
else
{
res = res*a;
b = b – 1;
}
}
return res;
}
From that explanation part you can understand the exponent operation, but to check the conditions, first while iteration is enough.
x = 2, y = 3, res = 2, a = 2, b = 2.
Only (C) satisfies these values.
xy = res * ab
23 = 2 * 22 = 8
Explanation:
Will compute for smaller values.
Let X = 2, Y = 3, res = 1
while (3 != 0)
{
if(3%2 == 0) – False
else
{
res = 1*2 = 2;
b = 3 – 1 = 2;
}
For options elimination, consider
return res = 2 (but it is out of while loop so repeat while)
__________
while (2 != 0)
{
if (2%2 == 0) – True
{
a = 2*2 = 4
b = 2/2 = 1
}
__________
repeat while
while (1 != 0)
{
if (1%2 == 0) – False
else
{
res = 2 * 4 = 8
b = 1 – 1 = 0
}
__________
while (0 != 0) – False
return res = 8 (23)
Question 24

Consider the following program:

    int f(int *p, int n)
    {
       if (n <= 1) return 0;
       else return max (f(p+1,n-1),p[0]-p[1]);
    }

    int main()
    {
       int a[] = {3,5,2,6,4};
       printf("%d", f(a,5));
    }
Note: max(x,y) returns the maximum of x and y.

The value printed by this program is __________.

A
3
B
4
C
5
D
6
       Programming       Programming       GATE 2016 [Set-2]       Video-Explanation
Question 24 Explanation: 
Given

f(a, 5) ⇒ f(100, 5)
Question 25

The output of the following C program is __________.

void f1 (int a, int b)
{
  int c;
  c=a; a=b; b=c;
}
void f2 (int *a, int *b)
{
  int c;
  c=*a; *a=*b;*b=c;
}
int main()
{
  int a=4, b=5, c=6;
  f1(a, b);
  f2(&b, &c);
  printf (“%d”, c-a-b);
  return 0;
}
A
-5
B
6
C
7
D
8
       Programming       Programming       GATE 2015 [Set-1]
Question 25 Explanation: 
Function f1 will not swap the value of ‘a’ and ‘b’ because f1 is call by value.
But f2 will swap the value of ‘b’ and ‘c’ because f2 is call by reference. So finally the value of
a=4
b=6
c=5
So, answer will be
c – a – b
5 – 4 – 6 = -5
Question 26

What is the output of the following C code? Assume that the address of x is 2000 (in decimal) and an integer requires four bytes of memory.

 
int main() { 
        unsigned int x[4][3] = 
          {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10, 11, 12}};
        printf("%u, %u, %u", x+3, *(x+3), *(x+2)+3);
}
A
2036, 2036, 2036
B
2012, 4, 2204
C
2036, 10, 10
D
2012, 4, 6
       Programming       Programming       GATE 2015 [Set-1]
Question 26 Explanation: 
⇒ Address of x = 2000
⇒ x [4] [3] can represents that x is a 2-dimensional array.
⇒ x+3 = (Address of x) + 3 * 4 * 3 [3×4×3 is inner dimention]
= 2000 + 36
= 2036
⇒ *(x+3) also returns the address i.e., 2036.
The ‘*’ represents 1 – D but x is starting at 2036.
⇒ *(x+3)+3 = *(Address of x + 2 * 3 * 4) + 3
= *(2000 + 24) +3
= *(2024) + 3 [‘*’ will change from 2D to 1D]
= 2024 + 3 * 4
= 2024 + 12
= 2036
Question 27

Consider the following pseudo code, where x and y are positive integers.

begin
   q := 0
   r := x
while r >= y do
   begin
      r := r – y
      q := q + 1
   end
end

The post condition that needs to be satisfied after the program terminates is

A
{r = qx+y ∧ r
B
{x = qy+r ∧ r
C
{y = qx+r ∧ 0
D
{q+10}
       Programming       Programming       GATE 2015 [Set-1]
Question 27 Explanation: 
The loop terminates when r In each iteration q is incremented by 1 and y is subtracted from ‘r’. Initial value of ‘r’ is ‘x’. So, loop iterates x/y times and q will be equal to x/y and r = x%y.
⇒ x = qy + r
Question 28

Consider the following C program segment.

while (first <= last)
{
   if (array [middle] < search)
      first = middle +1;
   else if (array [middle] == search)
      found = True;
   else last = middle – 1;
   middle = (first + last)/2;
}
if (first < last) not Present = True;

The cyclomatic complexity of the program segment is __________.

A
5
B
6
C
7
D
8
       Programming       Programming       GATE 2015 [Set-1]
Question 28 Explanation: 
Note: Out of syllabus.
Question 29

Consider the following C function.

int fun1 (int n)
{
   int i, j, k, p, q = 0;
   for (i = 1; i<n; ++i)
   {
      p = 0;
      for (j = n; j > 1; j = j/2)
         ++p;
      for (k = 1; k < p; k = k*2)
         ++q;
   }
   return q;
}

Which one of the following most closely approximates the return value of the function fun1?

A
n3
B
n(log n)2
C
nlog n
D
nlog (log n)
       Programming       Programming       GATE 2015 [Set-1]
Question 29 Explanation: 
for (i=1; i p=0;
for (j=n; j>1; j=j/2) — p = O(log n) ++p;
for (k=1; k ++q;
}
∴ The return value of the function fun1,
q = n log p
= n log log n
Question 30

Consider the following function written the C programming language.

       void foo(char *a) {
          if(*a && *a != ' ') {
              foo(a+1);
              putchar(*a);
           }
       }

The output of the above function on input “ABCD EFGH” is

A
ABCD EFGH
B
ABCD
C
HGFE DCBA
D
DCBA
       Programming       Programming       GATE 2015 [Set-2]
Question 30 Explanation: 

if condition fails
& returns controls
∴ DCBA will be pointed
Question 31

Consider the following C functions

      int fun(int n) {
          int x = 1, k;
          if(n == 1) return x;
          for(k = 1; k < n; ++k)
              x = x + fun(k) * fun(n - k);
          return x;
      }

The return value of fun(5) is _______.

A
51
B
52
C
53
D
54
       Programming       Programming       GATE 2015 [Set-2]
Question 31 Explanation: 
Recurrence Relation is
f(n) = 1; if n = 1
Question 32

Consider the C program below.

#include 
int *A, stkTop;
int stkFunc (int opcode, int val)
{
    static int size=0, stkTop=0;
    switch (opcode)
    {
    case -1:
        size = val;
        break;
    case 0:
        if (stkTop < size ) A[stkTop++]=val;
        break;
    default:
        if (stkTop) return A[--stkTop];
    }
    return -1;
}
int main()
{
    int B[20];
    A=B;
    stkTop = -1;
    stkFunc (-1, 10);
    stkFunc (0, 5);
    stkFunc (0, 10);
    printf ("%dn", stkFunc(1, 0)+ stkFunc(1, 0));
}

The value printed by the above program is ___________

A
-2
B
2
C
-1
D
15
       Programming       Programming       GATE 2015 [Set-2]
Question 32 Explanation: 
When first time stkFunc (-1,10) will be called then, inside Switch(opcode) the control will go to Case-I, where size = 10.
When next time stkFunc (0,5) is called then, inside Switch(opcode), the control will go to Case-0, where A[0] = 5 and stkTop = 0+1 = 1.
When next time stkFunc (0,10) is called then, inside Switch (opcode), the control will go to Case '0', where A[1] = 10 and stkTop = 1+1 = 2.
When next time stkFunc(1,0) is called from inside the printf statement, then inside Switch(opcode), the control will go to default and stkTop = 2-1 = 1 and value of A[1] will get returned, i.e., 10.
When next time stkFunc(1,0) is called from inside the printf statement, then inside Switch(opcode), the control will go to default and stkTop = 1-1 = 0 and value of A[0] will get returned, i.e., 5.
Finally the two values 10 & 5 will be added and printed.
Question 33

Consider the following C program segment.

# include 
int main( )
{
    char s1[7] = "1234", *p;
    p = s1 + 2;
    *p = '0' ;
    printf ("%s", s1);
} 

What will be printed by the program?

A
12
B
120400
C
1204
D
1034
       Programming       Programming       GATE 2015 [Set-3]
Question 33 Explanation: 
p = s1+2;
p now points to third element in s1, i.e., '3'.
*p = '0', will make value of '3' as '0' in s1. And finally s1 will become 1204.
Question 34

Consider the following recursive C function. If get(6) function is being called in main() then how many times will the get() function be invoked before returning to the main()?

void get (int n)
{
   if (n < 1) return;
   get(n-1);
   get(n-3);
   printf("%d", n);
}
A
15
B
25
C
35
D
45
       Programming       Programming       GATE 2015 [Set-3]
Question 34 Explanation: 
Question 35

Consider the following C program.

# include 
int main( )
{
  static int a[] = {10, 20, 30, 40, 50};
  static int *p[] = {a, a+3, a+4, a+1, a+2};
  int **ptr = p;
  ptr++;
  printf("%d%d", ptr - p, **ptr};
}

The output of the program is _________.

A
140
B
150
C
160
D
170
       Programming       Programming       GATE 2015 [Set-3]
Question 35 Explanation: 

**ptr = 40
∴ printf (“%d%d”, p + r – p, p + r) will print 140.
Question 36

Consider the following C program:

# include 
int main( )
{
   int i, j, k = 0;
   j = 2 * 3 / 4 + 2.0 / 5 + 8 / 5;
   k  -= --j;
   for (i = 0; i < 5; i++)
   {
      switch(i + k)
      {
         case 1:
         case 2: printf("n%d", i + k);
         case 3: printf("n%d", i + k);
         default: printf("n%d", i + k);
      }
   }
   return 0;
}

The number of times printf statement is executed is __________.

A
10
B
11
C
12
D
13
       Programming       Programming       GATE 2015 [Set-3]
Question 36 Explanation: 
j = 2*3 / 4+2.0 / 5+8 / 5;
= 6 / 4+2.0 / 5+1;
= 1 + 0.4 + 1
= 2.4
But since j is integer,
j=2
Now,
k = k - (--j)
k = 0 - (1) = -1
When i=0, i+k = -1,
printf executed 1 time
When i=1, i+k = 0,
printf executed 1 time
When i=2, i+k = 1,
printf executed 3 times
When i=3, i+k = 2,
printf executed 3 times
When i=4, i+k = 3,
printf executed 2 times
∴ Total no. of times printf executed is,
1 + 1 + 3 + 3 + 2 = 10
Question 37

Consider the following C program. The output of the program is __________.

# include 
int f1(void);
int f2(void);
int f3(void);
int x = 10;
int main()
{
    int x = 1;
    x += f1() + f2() + f3() + f2();
    pirntf("%d", x);
    return 0;
}
 
int f1()
{
    int x = 25;
    x++;
    return x;
}
 
int f2( )
{
    static int x = 50;
    x++;
    return x;
}
 
int f3( )
{
    x *= 10;
    return x;
}
A
230
B
240
C
250
D
260
       Programming       Programming       GATE 2015 [Set-3]
Question 37 Explanation: 
x = x + f1( ) + f2( ) + f3( ) + f4( )
f1( ) = 25 + 1 = 26
f2( ) = 50 + 1 = 51
f3( ) = 10 × 10 = 100
f2( ) = 51 × 1 = 52 (Since here x is static variable so old value retains)
∴ x = 1+26+51+100+52 = 230
Question 38

Consider the following program in C language:

#include 
main()
{
    int i;
    int *pi = &i;
    scanf("%d", pi);
    printf("%dn", i+5);
}

Which one of the following statements is TRUE?

A
Compilation fails.
B
Execution results in a run-time error.
C
On execution, the value printed is 5 more than the address of variable i.
D
On execution, the value printed is 5 more than the integer value entered.
       Programming       Programming       GATE 2014 [Set-1]
Question 38 Explanation: 
int i; // Initially i takes the Garbage value
int *pi = &i; // pi is a pointer which stores the address of i.
scanf (pi); // pi = &i (we rewrite the garbage value with our values) say x = 2
printf (i+5); // i+5 = x+5 = 2+5 = 7
Hence on execution, the value printed is 5 more than the integer value entered.
Question 39

Consider the function func shown below:

int func(int num)
{
    int count = 0;
    while (num)
    {
        count++;
        num >>= 1;
    }
    return (count);
}

The value returned by func(435)is __________.

A
9
B
10
C
11
D
12
       Programming       Programming       GATE 2014 [Set-2]
Question 39 Explanation: 
Shift right of 1, which means the number gets half.
Shift left of 1, which means the number gets doubled.
In program, shift right of 1 is given, means every time we enter the loop the number will get halved, and the value of count will get incremented by 1. And when the value of num will become zero then the while loop will get terminated. So,
num = 435/2 = 217/2 = 108/2 = 54/2 = 27/2= 13/2 = 6/2 = 3/2 = 1/2 = 0
Count = 9
So, the value count that will get returned is 9.
Question 40

Suppose n and p are unsigned int variables in a C program. We wish to set p to nC3. If n is large, which one of the following statements is most likely to set p  correctly?

A
p = n * (n-1) * (n-2) / 6;
B
p = n * (n-1) / 2 * (n-2) / 3;
C
p = n * (n-1) / 3 * (n-2) / 2;
D
p = n * (n-1) * (n-2) / 6.0;
       Programming       Programming       GATE 2014 [Set-2]
Question 40 Explanation: 
n & p are unsigned int variable.
From the options n*(n-1)*(n-2) will go out of range. So eliminate A & D.
n*(n-1) is always an even number. So subexpression n(n-1)/2 also an even number.
n*(n-1)/ 2*(n-2), gives a number which is a multiple of 3. So dividing with 3 will not have any loss. Hence B is option.
Question 41

Consider the following function

double f(double x){
  if (abs(x*x - 3) < 0.01) return x;
  else return f(x/2 + 1.5/x);
}

Give a value q (to 2 decimals) such that f(q) will return q:_____.

A
1.73
B
1.74
C
1.75
D
1.76
       Programming       Programming       GATE 2014 [Set-2]
Question 41 Explanation: 
f(q) will return q, if
x2 - 3 < 0.01 will become True.
So, x2 - 3 < 0.01
x2 - 3 < 0.01
x2 < 3.01
x < 1.732
Hence, x = 1.73.
Question 42

Consider the C function given below.

int f(int j)
{
  static int i = 50;
  int k;
  if (i == j)
  {
    printf(“something”);
    k = f(i);
    return 0;
  }
  else return 0;
}

Which one of the following is TRUE?

A
The function returns 0 for all values of j.
B
The function prints the string something for all values of j.
C
The function returns 0 when j = 50.
D
The function will exhaust the runtime stack or run into an infinite loop when j = 50.
       Programming       Programming       GATE 2014 [Set-2]
Question 42 Explanation: 
Let's say that value of j given inside the function is 50.
int f(int j)
{
static int i = 50;
int k;
if (i == j) // This will be True.
{
printf ("Something");
k = f(i); // Again called f(i) with value of i as 50. So, the function will run into infinite loop.
return 0;
}
else return 0;
}
Question 43

Let A be a square matrix of size n x n. Consider the following program. What is the expected output?

C = 100
for i = 1 to n do
    for j = 1 to n do
    {
        Temp = A[i][j] + C
        A[i][j] = A[j][i]
        A[j][i] = Temp - C
    } 
for i = 1 to n do
    for j = 1 to n do
        Output(A[i][j]);
A
The matrix A itself
B
Transpose of the matrix A
C
Adding 100 to the upper diagonal elements and subtracting 100 from lower diagonal elements of A
D
None of the above
       Programming       Programming       GATE 2014 [Set-3]
Question 43 Explanation: 
Let be a small matrix.
For first row iteration, it get swapped and becomes
For second row iteration, it comes to the original position
=A
So, it is the same matrix A.
Question 44

The minimum number of arithmetic operations required to evaluate the polynomial P(X) = X5 + 4X3 + 6X + 5 for a given value of X, using only one temporary variable is ________.

A
7
B
8
C
9
D
10
       Programming       Arithmetic-Expressions       GATE 2014 [Set-3]
Question 44 Explanation: 
The minimum number of arithmetic operations required to evaluate
P(X) = x5+4x3+6x+5
= x(x4+4x2+6)+5
= x(x(x3+4x)+6)+5
= x(x(x(x2+4))+6)+5
= x(x(x(x(x)+4))+6)+5
4 multiplications & 3 additions.
4 + 3 = 7
Question 45

Consider the following function:

int unknown(int n) {
    int i, j, k = 0;
    for (i  = n/2; i <= n; i++)
        for (j = 2; j <= n; j = j * 2)
            k = k + n/2;
    return k;
 }
A
Θ(n2)
B
Θ(n2 log n)
C
Θ(n3)
D
Θ(n3 logn)
       Programming       Programming       GATE 2013
Question 45 Explanation: 
Outer loop runs for (n/2) times and inner loop runs for (logn) times.
So, the total number of times loop runs is (n/2 logn).
So, the final k value will be n/2*(n/2 logn) = O(n2logn)
= (n/2+1).n/2 ∙log n
= (n2log n)
Question 46

Consider the following languages.

    L1 = {0p1q0r|p,q,r≥0}
    L2 = {0p1q0r|p,q,r≥0, p≠r}

Which one of the following statements is FALSE?

A
L2 is context-free.
B
L1∩ L2 is context-free.
C
Complement of L2 is recursive.
D
Complement of L1 is context-free but not regular.
       Programming       CFL&PDA       GATE 2013
Question 46 Explanation: 
L1 = 0*1*0* which is regular language and in L2 we have one comparison (i.e. p ≠ r) so it is CFL.
Intersection of a regular language with a context free language is context free language (by closure properties of regular language) So L1∩ L2 is context-free.
L2 is CFL and CFL is not closed under complementation so we have to assume L2 as CSL (since every CFL is CSL) and CSL is closed under complement so Complement of L2 must be CSL and every CSL is recursive so Complement of L2 is recursive.
Since L1 is regular and regular language is closed under complement so complement of L1 must be regular and hence the statement Complement of L1 is context-free but not regular is a false statement.
Question 47

The procedure given below is required to find and replace certain characters inside an input character string supplied in array A. The characters to be replaced are supplied in array oldc, while their respective replacement characters are supplied in array newc. Array A has a fixed length of five characters, while arrays oldc and newc contain three characters each. However, the procedure is flawed

void find_and_replace(char *A, char *oldc, char *newc) {
    for (int i = 0; i < 5; i++)
       for (int j = 0; j < 3; j++)
           if (A[i] == oldc[j]) A[i] = newc[j];
}

The procedure is tested with the following four test cases

(1) oldc = "abc", newc = "dab" 
(2) oldc = "cde", newc = "bcd" 
(3) oldc = "bca", newc = "cda" 
(4) oldc = "abc", newc = "bac" 

If array A is made to hold the string “abcde”, which of the above four sest cases will be successful in exposing the flaw in this procedure?

A
None
B
2 only
C
3 and 4 only
D
4 only
       Programming       Programming       GATE 2013
Question 47 Explanation: 
The test cases 3 & 4 captures the flaw. The code does not works fine when an old character is replaced by a new character & new character is again replaced by another new character.
1, 2 works fine, 3, 4 carries flaw.
Question 48

What will be the output of the following C program segment?

char inchar = 'A';
switch (inchar)
{
case 'A' :
    printf ("choice A n") ;
case 'B' :
    printf ("choice B ") ;
case 'C' :
case 'D' :
case 'E' :
default:
    printf ("No Choice") ;
}
A
No Choice
B
Choice A
C
D
Program gives no output as it is erroneous
       Programming       C-Programming       GATE 2012
Question 48 Explanation: 
Everything in the switch will be executed, because there is no break; statement after case ‘A’. So it executes all the subsequent statements until it find a break;
So,
→ Choice A
→ Choice B. No choice. Is the output.
Question 49

Consider the following C program

int a, b, c = 0;
void prtFun (void);
int main ()
{
    static int a = 1; /* line 1 */
    prtFun();
    a += 1;
    prtFun();
    printf ( "n %d %d " , a, b) ;
}
  
void prtFun (void)
{
    static int a = 2; /* line 2 */
    int b = 1;
    a += ++b;
    printf (" n %d %d " , a, b);
}

What output will be generated by the given code segment?

A
B
C
D
       Programming       C-Programming       GATE 2012
Question 49 Explanation: 

Hence
4 2
6 2
2 0
Question 50

Consider the following C program

int a, b, c = 0;
void prtFun (void);
int main ()
{
    static int a = 1; /* line 1 */
    prtFun();
    a += 1;
    prtFun();
    printf ( "n %d %d " , a, b) ;
}
  
void prtFun (void)
{
    static int a = 2; /* line 2 */
    int b = 1;
    a += ++b;
    printf (" n %d %d " , a, b);
}

What output will be generated by the given code segment if:

    Line 1 is replaced by auto int a = 1;
    Line 2 is replaced by register int a = 2;
A
B
C
D
       Programming       C-Programming       GATE 2012
Question 50 Explanation: 
Line 1 replaced by auto int a=1;
Line 2 replaced by register int a=2;
In main there will be no change if it is static or auto because of a+=1 the auto variable a is updated to 2 from 1.
In prtfun ( ), register makes a difference.
For first print statement a is updated to 4 & prints 4, 2.
But now it is not a static variable to retain the value of a to 4. So it becomes 2, when second function call takes place & prints 4, 2 again. There is no change in b, it acts like a local variable.
Hence,
4 2
4 2
2 0.
There are 50 questions to complete.

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