Why storage classes are needed - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with automatic storage class.

C

void function() {
    [1] int x = 10;
}

Drag options to blanks, or click blank then click option'

Astatic

Bauto

Cextern

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using static instead of auto inside functions.

The auto keyword declares a variable with automatic storage, which is the default inside functions.

2fill in blank

medium

Complete the code to declare a variable with static storage class inside a function.

C

void counter() {
    [1] int count = 0;
    count++;
    printf("%d", count);
}

Drag options to blanks, or click blank then click option'

Aauto

Bregister

Cextern

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using auto which resets the variable each call.

The static keyword inside a function makes the variable keep its value between calls.

3fill in blank

hard

Fix the error in the code by choosing the correct storage class for a global variable.

C

[1] int global_var = 5;

void func() {
    printf("%d", global_var);
}

Drag options to blanks, or click blank then click option'

Aextern

Bauto

Cstatic

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using extern which declares a variable defined elsewhere.

Using static for a global variable limits its scope to the file, which is often needed to avoid conflicts.

4fill in blank

hard

Fill both blanks to declare an external variable and use it in another file.

C

// file1.c
[1] int shared_var = 100;

// file2.c
[2] int shared_var;

void print_var() {
    printf("%d", shared_var);
}

Drag options to blanks, or click blank then click option'

Aextern

Bstatic

Cauto

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using static in both files which hides the variable.

In file1.c, static limits the variable to that file, so it should be removed to share it. The correct is to declare normally (no static) in file1.c and extern in file2.c to access it.

5fill in blank

hard

Fill all three blanks to declare a register variable, use it in a loop, and print its value.

C

void loop() {
    [1] int i;
    for (i = 0; i [2] 5; i++) {
        printf("%d ", i);
    }
    printf("\nValue of i: %d", [3]);
}

Drag options to blanks, or click blank then click option'

Aregister

B<

Ci

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using static inside the loop which changes variable lifetime.

register suggests storing the variable in a CPU register for faster access. The loop runs while i < 5, and printing i shows its final value.