Scope of variables - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a global variable.

C

#include <stdio.h>

[1] count = 10;

int main() {
    printf("Count is %d\n", count);
    return 0;
}

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

Aextern

Bint

Cstatic

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'static' limits the variable to the file scope but is not necessary here.

Using 'extern' without defining the variable causes linker errors.

Using 'register' is only for local variables and hints to store in CPU registers.

The keyword int declares the variable count as a global integer variable accessible throughout the file.

2fill in blank

medium

Complete the code to declare a local variable inside main.

C

#include <stdio.h>

int main() {
    [1] number = 5;
    printf("Number is %d\n", number);
    return 0;
}

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

Aint

Bstatic

Cextern

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extern' inside a function is incorrect for local variables.

Using 'static' inside a function changes the variable lifetime but is not required here.

Using 'register' is optional and hints to store in CPU registers.

The keyword int declares a local integer variable number inside the main function.

3fill in blank

hard

Fix the error in the code by choosing the correct keyword for the variable inside the function.

C

#include <stdio.h>

int count = 20;

int main() {
    [1] count = 10;
    printf("Count is %d\n", count);
    return 0;
}

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

Aint

Bstatic

Cextern

Dregister

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extern' inside a function without definition causes errors.

Using 'static' changes lifetime but is not necessary here.

Using 'register' is optional and unrelated to the error.

Declaring int count = 10; inside main creates a local variable that hides the global count. This is valid and fixes the error.

4fill in blank

hard

Fill both blanks to declare a static variable inside a function and initialize it.

C

#include <stdio.h>

void func() {
    [1] int counter = [2];
    counter++;
    printf("Counter: %d\n", counter);
}

int main() {
    func();
    func();
    return 0;
}

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

Astatic

B10

C0

Dextern

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extern' inside a function is invalid.

Initializing static variables to 10 will start counting from 10, not zero.

Not using 'static' will reset the variable each call.

Using static makes counter keep its value between calls. Initializing it to 0 starts counting from zero.

5fill in blank

hard

Fill all three blanks to create a function that modifies a global variable.

C

#include <stdio.h>

[1] total = 0;

void add(int value) {
    total [2]= value;
}

int main() {
    add([3]);
    printf("Total: %d\n", total);
    return 0;
}

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

Astatic

B+

C5

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'static' for global variable limits its scope to the file.

Using '-' instead of '+' will subtract instead of add.

Calling add with no argument or wrong value causes errors.

Declare total as a global int. Use += to add value to total. Call add(5) to add 5 to total.