Macro Substitution - C Preprocessor Questions and Answers

This set of C Multiple Choice Questions & Answers (MCQs) focuses on “Macro Substitution – 1”.

Pre-requisite for this C MCQ set: Advanced C Programming Video Tutorial.

1. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    #define foo(m, n) m ## n
```
```
    int main()
```
```
    {
```
```
        printf("%s\n", foo(k, l));
```
```
    }
```

a) k l
b) kl
c) Compile time error
d) Undefined behaviour
View Answer

Answer: c
Explanation: None.

2. What will be the output of the following C code?

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```
    #include <stdio.h>
```
```
    #define foo(m, n) " m ## n "
```
```
    int main()
```
```
    {
```
```
        printf("%s\n", foo(k, l));
```
```
    }
```

a) k l
b) kl
c) Compile time error
d) m ## n
View Answer

Answer: d
Explanation: None.

3. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    #define foo(x, y) #x #y
```
```
    int main()
```
```
    {
```
```
        printf("%s\n", foo(k, l));
```
```
        return 0;
```
```
    }
```

a) kl
b) k l
c) xy
d) Compile time error
View Answer

Answer: a
Explanation: None.

4. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    #define foo(x, y) x / y + x
```
```
    int main()
```
```
    {
```
```
        int i = -6, j = 3;
```
```
        printf("%d\n",foo(i + j, 3));
```
```
        return 0;
```
```
    }
```

a) Divided by zero exception
b) Compile time error
c) -8
d) -4
View Answer

Answer: c
Explanation: None.

5. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    void f();
```
```
    int main()
```
```
    {
```
```
        #define foo(x, y) x / y + x
```
```
        f();
```
```
    }
```
```
    void f()
```
```
    {
```
```
        printf("%d\n", foo(-3, 3));
```
```
    }
```

a) -8
b) -4
c) Compile time error
d) Undefined behaviour
View Answer

Answer: b
Explanation: None.

6. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    void f();
```
```
    int main()
```
```
    {
```
```
        #define max 10
```
```
        f();
```
```
        return 0;
```
```
    }
```
```
    void f()
```
```
    {
```
```
        printf("%d\n", max * 10);
```
```
    }
```

a) 100
b) Compile time error since #define cannot be inside functions
c) Compile time error since max is not visible in f()
d) Undefined behaviour
View Answer

Answer: a
Explanation: None.

7. What will be the output of the following C code?

```
    #include <stdio.h>
```
```
    #define foo(x, y) x / y + x
```
```
    int main()
```
```
    {
```
```
        int i = -6, j = 3;
```
```
        printf("%d ", foo(i + j, 3));
```
```
        printf("%d\n", foo(-3, 3));
```
```
        return 0;
```
```
    }
```

a) -8 -4
b) -4 divided by zero exception
c) -4 -4
d) Divided by zero exception
View Answer

Answer: a
Explanation: None.

8. What will be the output of the following C code?

```
 #include <stdio.h>
```
```
    int foo(int, int);
```
```
    #define foo(x, y) x / y + x
```
```
    int main()
```
```
    {
```
```
        int i = -6, j = 3;
```
```
        printf("%d ",foo(i + j, 3));
```
```
        #undef foo
```
```
        printf("%d\n",foo(i + j, 3));
```
```
    }
```
```
    int foo(int x, int y)
```
```
    {
```
```
        return x / y + x;
```
```
    }
```

a) -8 -4
b) Compile time error
c) -8 -8
d) Undefined behaviour
View Answer

Answer: a
Explanation: None.

9. What is the advantage of #define over const?
a) Data type is flexible
b) Can have a pointer
c) Reduction in the size of the program
d) None of the mentioned
View Answer

Answer: a
Explanation: None.

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