Difference between revisions of "C Coding Questions"

1. What is the output of this program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   char *ptr;
   char string[] = "How are you?";
   ptr = string;
   ptr += 4;
   printf("%s",ptr);
   
   return 0;

} </syntaxhighlight> (a) How are you?

(b) are you?

(c) are

(d) No output

2. Which of the following will print the value 2 for the above code? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a[10][20][30] = {0};
   a[5][2][1] = 2;

   return 0;

} </syntaxhighlight> (a) printf("%d",*(((a+5)+2)+1));

(b) printf("%d",***((a+5)+2)+1);

(c) printf("%d",*(*(*(a+5)+2)+1));

(d) None of these

3. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 5;
   int b = ++a * a++;
   printf("%d ",b);
   return 0;

} </syntaxhighlight> (a)25

(b) 30

(c) 36

(d) Undefined Behavior

4. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 5;
   switch(a)
   {
       default:
       a = 4;
       case 6:
           a--;
       case 5:
           a = a+1;
       case 1:
           a = a-1;
   }
   printf("%d \n",a);

   return 0;

} </syntaxhighlight> (a)5

(b) 4

(c) 3

(d) None of these

5. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 2,b = 5;
   a = a^b;
   b = b^a;
   printf("%d %d",a,b);

   return 0;

} </syntaxhighlight> (a)5 2

(b) 2 5

(c) 7 7

(d) 7 2

6. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int main() {

   int a[][3] = {1, 2, 3, 4, 5, 6};
   int (*ptr)[3] = a;
   printf("%d %d ", (*ptr)[1], (*ptr)[2]);
   ++ptr;
   printf("%d %d\n", (*ptr)[1], (*ptr)[2]);

   return 0;

} </syntaxhighlight> (a)2 3 5 6

(b) 2 3 4 5

(c) 4 5 0 0

(d) none of the above

7. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

void f(char**);

int main() {

   char *argv[] = { "ab", "cd", "ef", "gh", "ij", "kl" };
   f(argv);

   return 0;

} void f(char **p) {

   char *t;
   t = (p += sizeof(int))[-1];
   printf("%s\n", t);

} </syntaxhighlight> (a)ab

(b) cd

(c) ef

(d) gh

8. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdarg.h>
2. include <stdio.h>

int ripple(int n, ...) {

   int i, j, k;
   va_list p;
   k = 0;
   j = 1;
   va_start(p, n);
   for (; j < n; ++j)
   {
       i = va_arg(p, int);
       k += i;
   }
   va_end(p);
   
   return k;

} int main() {

   printf("%d\n", ripple(3, 5, 7));

   return 0;

} </syntaxhighlight> (a)12

(b) 5

(c) 7

(d) 15

9. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int counter(int i) {

   static int count = 0;
   count = count + i;
   
   return count;

}

int main() {

   int i, j;
   for (i = 0; i <= 5; i++)
       j = counter(i);
   printf("%d\n", j);

   return 0;

} </syntaxhighlight> (a)10

(b) 15

(c) 6

(d) 7

10. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   const int x = 5;
   const int *ptrx;
   ptrx = &x;
   *ptrx = 10;
   printf("%d\n", x);

   return 0;

} </syntaxhighlight> (a)5

(b) 10

(c) Compile Error

(d) Garbage value

11. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>
2. define x 4+1

int main() {

   int i;
   i = x*x*x;
   printf("%d",i);

   return 0;

} </syntaxhighlight> (a)125

(b) 13

(c) 17

(d) None of above

12. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   char c=125;
   c=c+10;
   printf("%d",c);

   return 0;

} </syntaxhighlight> (a)135

(b) +INF

(c) -121

(d) -8

13. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int i=10;
   static int x=i;
   if(x==i)
       printf("Equal");
   else if(x>i)
       printf("Greater");
   else
       printf("Lesser");

   return 0;

} </syntaxhighlight> (a)Equal

(b) Greater

(c) Lesser

(d) Compile Error

14. Consider the following code segment: <syntaxhighlight lang="c">

1. include <stdlib.h>

int *f1() {

   int x = 10;
   return &x;

} int *f2() {

   int *ptr;
   *ptr = 10;
   return ptr;

} int *f3() {

   int *ptr;
   ptr = (int*) malloc(sizeof (*ptr));
   return ptr;

} </syntaxhighlight> Which of these functions uses pointers incorrectly?

(a)f3 only

(b) f1 and f3

(c) f1 and f2

(d) f1, f2, and f3

15. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int main() {

   int i = 3;
   int j;
   j = sizeof(++i + ++i);
   printf("i=%d j=%d\n", i, j);

   return 0;

} </syntaxhighlight> (a)i=4 j=4

(b) i=3 j=4

(c) i=5 j=4

(d) the behavior is undefined

16. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

void f1(int*, int); void f2(int*, int); void (*p[2])(int*, int);

int main() {

   int a = 3;
   int b = 5;
   p[0] = f1;
   p[1] = f2;
   p[0](&a, b);
   printf("%d %d ", a, b);
   p[1](&a, b);
   printf("%d %d\n", a, b);

   return 0;

}

void f1(int *p, int q) {

   int tmp = *p;
   *p = q;
   q = tmp;

} void f2(int *p, int q) {

   int tmp = *p;
   *p = q;
   q = tmp;

} </syntaxhighlight> (a)5 5 5 5

(b) 3 5 3 5

(c) 5 3 3 5

(d) none of the above

17. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

void e(int);

int main() {

   int a = 3; 
   e(a);
   putchar('\n');

   return 0;

} void e(int n) {

   if (n > 0)
   {
       e(--n);
       printf("%d ", n);
       e(--n);
   }

} </syntaxhighlight> (a)0 1 2 0

(b) 0 1 2 1

(c) 1 2 0 1

(d) 0 2 1 1

18. Consider the following code segment: <syntaxhighlight lang="c"> typedef int (*test)(float*, float*); test tmp; </syntaxhighlight> What is the type of tmp?

(a)function taking two pointer-to-float arguments and returning pointer to int

(b) pointer to int

(c) pointer to function taking two pointer-to-float arguments and returning int

(d) none of the above

19. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int main() {

   char p;
   char buf[10] = {1, 2, 3, 4, 5, 6, 9, 8};
   p = (buf + 1)[5];
   printf("%d\n", p);

   return 0;

} </syntaxhighlight> (a)5

(b) 6

(c) 9

(d) none of the above

20. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int main() {

   struct node
   {
       int a;
       int b;
       int c;
   };
   struct node s = { 3, 5, 6 };
   struct node *pt = &s;
   printf("%d\n", *((int*)pt+1));

   return 0;

} </syntaxhighlight> (a)3

(b) 5

(c) 6

(d) 7

21. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

int main(void) {

   char a[5] = { 1, 2, 3, 4, 5 };
   char *ptr = (char*)(&a + 1);
   printf("%d %d\n", *(a + 1), *(ptr - 1));

   return 0;

} </syntaxhighlight> (a)Compile Error

(b) 2 1

(c) 2 5

(d) none of the above

22. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>

void foo(int[][3]);

int main(void) {

   int a[3][3] = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
   foo(a);
   printf("%d\n", a[2][1]);

   return 0;

}

void foo(int b[][3]) {

   ++b;
   b[1][1] = 9;

} </syntaxhighlight> (a)8

(b) 9

(c) 7

(d) none of the above

23. Consider the following function: <syntaxhighlight lang="c"> int foo(int x, int n) {

   int val = 1;
   if (n > 0)
   {
       if (n % 2 == 1)
       val *= x;
       val *= foo(x * x, n / 2);
   }
   return val;

} </syntaxhighlight> What function of x and n is computed by foo? (a)x^n

(b) x×n

(c) nx

(d) none of the above

24. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 0;
   switch(a)
   {
       default:
           a = 4;
       case 6:
           a--;
       case 5:
           a = a+1;
       case 1:
           a = a-1;
   }
   printf("%d \n",a);

   return 0;

} </syntaxhighlight> (a)5

(b) 4

(c) 3

(d) 0

25. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 2;
   if(a == (1,2))
       printf("Hello");
   if(a == 1,2)
       printf("World");

   return 0;

} </syntaxhighlight> (a)Hello

(b) World

(c) Hello World

(d) Compile Error

26. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a = 1,2;
   int b = (1,2);
   if(a == b)
       printf("Equal");
   else
       printf("Not Equal");

   return 0;

} </syntaxhighlight> (a)Equal

(b) Not Equal

(c) Compiler Dependent

(d) Compile Error

27. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

void foo(char *);

int main() {

   char *string = "Hello";
   foo(string);
   printf("%s",string);

   return 0;

}

void foo(char *a) {

   while(*a)
   {
       *a += 1;
       a++;
   }

} </syntaxhighlight> (a)Hello

(b) Ifmmp

(c) Compile Error

(d) Segmentation fault

28. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>
2. include<stdlib.h>

int main() {

   char s[] = "Opendays2012";
   int i = 0;
   while(*(s++))
       i++;
   printf("%d",i);

   return 0;

} </syntaxhighlight> (a)Segmentation Fault

(b) Compile Error

(c) 12

(d) 0

29. What is the output of the following program? <syntaxhighlight lang="c">

1. include<stdio.h>

int a = 10; int main() {

   fun();
   fun();

   return 0;

}

int fun() {

   static int a = 1;
   printf("%d ",a);
   a++;

   return 0;

} </syntaxhighlight> (a)1 2

(b) 1 1

(c) 10 11

(d) 10 10

30. What is the output of the following program? <syntaxhighlight lang="c">

1. include <stdio.h>
2. define crypt(s,t,u,m,p,e,d) m##s##u##t
3. define begin crypt(a,n,i,m,a,t,e)

int begin() {

   printf("Hello\n");

   return 0;

} </syntaxhighlight> (a)Hello

(b) Link error

(c) Segmentation fault

(d) Compiler error

31. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a[10][20][30]={0};
   printf("%ld",&a+1 - &a);

   return 0;

} </syntaxhighlight> What is the output of this program? Ans:

32. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a[10][20][30] = {0};
   int *b = a;
   int *c = a+1;
   printf("%ld", c-b);

   return 0;

} </syntaxhighlight> What is the output of this program? (You may ignore compiler warnings)

Ans:

33. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>
2. include<stdlib.h>

int* fun();

int main() {

   int *a = fun();
   printf("%d",*a);

   return 0;

} int* fun() {

   int *a =(int*) malloc(sizeof(int));
   *a = 10;
   return a;

} </syntaxhighlight> What is the output of this program? Ans:

34. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int *a = fun();
   printf("%d",*a);

   return 0;

} int fun() {

   int a = 10;
   return a;

} </syntaxhighlight> What is the output of this program? Ans:

35. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>
2. include<string.h>

int main() {

   char string[] = "Hello";
   printf("%lu %lu",sizeof(string),strlen(string));

   return 0;

} </syntaxhighlight> What is the output of this program? Ans:

36. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   float a = 0.5;
   if(a == 0.5)
       printf("Yes");
   else
       printf("No");

   return 0;

} </syntaxhighlight> What is the output of this program? Ans:

37. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>
2. include<string.h>

void foo(char *);

int main() {

   char a[100] = {0};
   printf("%lu %lu",sizeof(a),strlen(a));

   return 0;

} </syntaxhighlight> What is the output of this program? Ans:

38. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   int a;
   printf("%d",scanf("%d",&a));

   return 0;

} </syntaxhighlight> What is the output of the above code?

Ans:

39. If the binary equivalent of 5.375 in normalised form is 0100 0000 1010 1100 0000 0000 0000 0000, what will be the output of the program ? <syntaxhighlight lang="c">

1. include<stdio.h>
2. include<math.h>

int main() {

   float a=5.375;
   char *p;
   int i;
   p = (char*)&a;
   for(i=0; i<2; i++)
       printf("%02x ", (unsigned char)(p[i]^p[3-i]));

   return 0;

} </syntaxhighlight> Ans:

40. Consider the following program: <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   char str[] = {'a','b','c','\0'};
   str[0] -= 32;
   printf("%s",str);

   return 0;

} </syntaxhighlight> What is the output of the above code?

Ans:

41. What is the following function doing? <syntaxhighlight lang="c"> int foo(int n) {

   int sum = 0;
   while(n > 0)
   {
       n = n & n-1;
       sum++;
   }
   return sum;

} </syntaxhighlight> Ans:

42. What is the following function doing? <syntaxhighlight lang="c"> int foo(int a, int b) {

   int c = a, d = b;
   while(a != b)
   {
       if(a < b)
           a = a+c;
       else
           b = b+d;
   }
   return a;

} </syntaxhighlight> Ans:

43. What is the following function doing? <syntaxhighlight lang="c"> int foo( int a, int b) {

   int c = a-b;
   c = c&(0x80000000);
   return (!c)*a +(!!c)*b;

} </syntaxhighlight> Ans:

44. What is the following function doing? <syntaxhighlight lang="c"> unsigned fun(unsigned a, unsigned b) {

   int i;
   unsigned  j = 0;
   for(i = 0; i < 32; i++)
   {
       j <<= 1;
       j += !!(a & 0x80000000);
       a <<= 1;
       if(j >=b)
       {
           j -= b;
           a++;
       }
   }
   return a;

} </syntaxhighlight> Ans:

45. What is the following function doing? <syntaxhighlight lang="c"> unsigned fun(unsigned int a) {

   unsigned int i, x = 0, y = 0, z = 0;
   for(i = 0; i < 16; i++)
   {
      	y <<= 2;
      	y += !!(a & 0x80000000) << 1;
      	y += !!(a & 0x40000000);
      	a <<= 2;
      	x = x + (x&1);
      	x <<= 1;
      	z <<= 1;
      	if(x + 1 <= y)
      	{
           x++;
           z++;

y-=x;

       }
   }
   return z;

} </syntaxhighlight> Ans:

46. Write the code to dynamically allocate a 2-D array of size m x n.

Ans:

47. Declare a pointer to a function accepting an integer and returning void.

Ans:

48. Write the condition so that the below code outputs “Hello World”. <syntaxhighlight lang="c">

1. include<stdio.h>

int main() {

   if(<condition>)
   {

printf("Hello ");

   }
   else
   {

printf("World\n");

   }

   return 0;

} </syntaxhighlight> Ans:

49. Write a one line code to check if a number is a power of 2.

Ans:

50. Write a one line code to invert the last four bits of an integer.

Ans:

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