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3.8 Exercises

1. What will the following code do?

   #define SQ(x) x * x;
        printf("%d\n", SQ(3));

2. What will the following code do?

   #define SQ(x) x * x;
        printf("%d\n", SQ(2+3));

3. What will be the output of the following code:

   #define DEBUG 0
        #define TWICEZ  z + z
   
        main()
        {    int z = 5;
   
             #ifdef DEBUG
                  printf("%d\n", TWICEZ * 2);
             #endif
        }

4. Check the following program for errors, if any, and use a manual trace to verify the program averages two numbers.

   #include <stdio.h>
        main()
        {    float x, y, average;
   
             printf("Type two numbers: ");
             scanf("%f %f", &x, &y);
             calc_avg(x, y);
             printf("Average of %f and %f is %f\n", x, y, average);
        }
   
        calc_avg(float a, float b)
        {
             return a + b / 2;
        }

5. Check the following program for errors, if any, and manually trace its execution.

   main()
        {    float x, y, average;
   
             printf("Type numbers\n");
             scanf("%f", &x);
             while (x != EOF) {
                  printf("Number read = %f\n", x);
                  scanf("%f", &x);
             }
        }