Why storage classes are needed - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable with static storage class

What is the output of this C program?

C

#include <stdio.h>

void func() {
    static int count = 0;
    count++;
    printf("%d ", count);
}

int main() {
    for(int i = 0; i < 3; i++) {
        func();
    }
    return 0;
}

A 3 3 3

B 0 1 2

C 1 1 1

D 1 2 3

💡 Hint

Think about how static variables keep their value between function calls.

The static keyword makes the variable count keep its value between calls to func(). So each time func() is called, count increases by 1, printing 1, then 2, then 3.

🧠 Conceptual

intermediate

Purpose of storage classes in C

Why are storage classes needed in C programming?

A To define the data type of variables

B To specify the scope, lifetime, and visibility of variables and functions

C To allocate memory dynamically during runtime

D To perform arithmetic operations on variables

💡 Hint

Think about what controls where and how long a variable exists.

Storage classes in C control the scope (where a variable can be accessed), lifetime (how long it exists), and visibility (which parts of the program can see it) of variables and functions.

🔧 Debug

advanced

Identify the error related to storage class

What error will this code produce and why?

C

#include <stdio.h>

int main() {
    extern int x;
    printf("%d", x);
    return 0;
}

A Linker error: undefined reference to 'x'

B Runtime error: segmentation fault

C Compilation error: 'extern' cannot be used inside main

D Output: 0

💡 Hint

Check if the variable 'x' is defined anywhere.

The variable x is declared as extern but never defined anywhere. This causes a linker error because the linker cannot find the actual variable.

📝 Syntax

advanced

Which option correctly declares a register variable?

Which of the following is the correct way to declare a register variable in C?

A register count int = 10;

B int register count = 10;

C register int count = 10;

D int count register = 10;

💡 Hint

The storage class specifier comes before the type.

The correct syntax is register int count = 10;. The storage class register must come before the type.

❓ Predict Output

expert

Output of code with auto and static variables

What is the output of this C program?

C

#include <stdio.h>

void test() {
    auto int a = 5;
    static int b = 5;
    a++;
    b++;
    printf("%d %d\n", a, b);
}

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

A

6 6
6 7

B

6 6
7 7

C

5 6
6 7

D

6 5
6 6

💡 Hint

Remember how auto and static variables behave inside functions.

The auto variable a is reinitialized to 5 each call, then incremented to 6. The static variable b keeps its value between calls, so it increments from 5 to 6 on first call, then from 6 to 7 on second call.