Register Variables - C Language Questions and Answers

This set of C Multiple Choice Questions & Answers (MCQs) focuses on “Register Variables – 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>
```
```
    int main()
```
```
    {
```
```
        register int i = 10;
```
```
        int *p = &i;
```
```
        *p = 11;
```
```
        printf("%d %d\n", i, *p);
```
```
    }
```

a) Depends on whether i is actually stored in machine register
b) 10 10
c) 11 11
d) Compile time error
View Answer

Answer: d
Explanation: None.

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2. register keyword mandates compiler to place it in machine register.
a) True
b) False
c) Depends on the standard
d) None of the mentioned
View Answer

Answer: b
Explanation: None.

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

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        register static int i = 10;
```
```
        i = 11;
```
```
        printf("%d\n", i);
```
```
    }
```

a) 10
b) Compile time error
c) Undefined behaviour
d) 11
View Answer

Answer: b
Explanation: None.

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

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        register auto int i = 10;
```
```
        i = 11;
```
```
        printf("%d\n", i);
```
```
    }
```

a) 10
b) Compile time error
c) Undefined behaviour
d) 11
View Answer

Answer: b
Explanation: None.

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

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        register const int i = 10;
```
```
        i = 11;
```
```
        printf("%d\n", i);
```
```
    }
```

a) 10
b) Compile time error
c) Undefined behaviour
d) 11
View Answer

Answer: b
Explanation: None.

6. Register storage class can be specified to global variables.
a) True
b) False
c) Depends on the compiler
d) Depends on the standard
View Answer

Answer: b
Explanation: None.

7. Which among the following is wrong for “register int a;”?
a) Compiler generally ignores the request
b) You cannot take the address of this variable
c) Access time to a is critical
d) None of the mentioned
View Answer

Answer: d
Explanation: None.

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