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  • Question
  • What will be the output of the program?
    #include<stdio.h>
    #define SWAP(a, b) int t; t=a, a=b, b=t;
    int main()
    {
        int a=10, b=12;
        SWAP(a, b);
        printf("a = %d, b = %d\n", a, b);
        return 0;
    }
    


  • Options
  • A. a = 10, b = 12
  • B. a = 12, b = 10
  • C. Error: Declaration not allowed in macro
  • D. Error: Undefined symbol 't'

  • Correct Answer
  • a = 12, b = 10 

    Explanation
    The macro SWAP(a, b) int t; t=a, a=b, b=t; swaps the value of the given two variable.

    Step 1: int a=10, b=12; The variable a and b are declared as an integer type and initialized to 10, 12 respectively.

    Step 2: SWAP(a, b);. Here the macro is substituted and it swaps the value to variable a and b.

    Hence the output of the program is 12, 10.


    More questions

    • 1. In C all functions except main() can be called recursively.

    • Options
    • A. True
    • B. False
    • Discuss
    • 2. Input/output function prototypes and macros are defined in which header file?

    • Options
    • A. conio.h
    • B. stdlib.h
    • C. stdio.h
    • D. dos.h
    • Discuss
    • 3. For a function receives variable number of arguments it is necessary that the function should receive at least one fixed argument.

    • Options
    • A. True
    • B. False
    • Discuss
    • 4. What will be the output of the program?
      #include<stdio.h>
      int X=40;
      int main()
      {
          int X=20;
          printf("%d\n", X);
          return 0;
      }
      

    • Options
    • A. 20
    • B. 40
    • C. Error
    • D. No Output
    • Discuss
    • 5. What will be the output of the program (myprog.c) given below if it is executed from the command line?
      cmd> myprog one two three
      /* myprog.c */
      #include<stdio.h>
      #include<stdlib.h>
      
      int main(int argc, char **argv)
      {
          int i;
          for(i=1; i<=3; i++)
              printf("%u\n", &argv[i]);
          return 0;
      }
      
      If the first value printed by the above program is 65517, what will be the rest of output?


    • Options
    • A. 65525 65531
    • B. 65519 65521
    • C. 65517 65517
    • D. 65521 65525
    • Discuss
    • 6. What will be the output of the program?
      #include<stdio.h>
      #include<stdlib.h>
      
      int main()
      {
          int *p;
          p = (int *)malloc(20); /* Assume p has address of 1314 */
          free(p);
          printf("%u", p);
          return 0;
      }
      

    • Options
    • A. 1314
    • B. Garbage value
    • C. 1316
    • D. Random address
    • Discuss
    • 7. Size of short integer and long integer would vary from one platform to another.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. Names of functions in two different files linked together must be unique

    • Options
    • A. True
    • B. False
    • Discuss
    • 9. What will be the output of the program?
      #include<stdio.h>
      
      int main()
      {
          int arr[2][2][2] = {10, 2, 3, 4, 5, 6, 7, 8};
          int *p, *q;
          p = &arr[1][1][1];
          q = (int*) arr;
          printf("%d, %d\n", *p, *q);
          return 0;
      }
      

    • Options
    • A. 8, 10
    • B. 10, 2
    • C. 8, 1
    • D. Garbage values
    • Discuss
    • 10. The macro va_arg is used to extract an argument from the variable argument list and advance the pointer to the next argument.

    • Options
    • A. True
    • B. False
    • Discuss


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