Variable declaration and initialization - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of uninitialized local variable

What is the output of this C code snippet?

C

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

A 0

B Compilation error

C 1

D Garbage value (undefined behavior)

💡 Hint

Local variables in C are not automatically initialized.

Local variables declared without initialization contain garbage values, leading to undefined behavior when printed.

❓ Predict Output

intermediate

Value of global variable after declaration

What will be printed by this C program?

C

int x;

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

A 0

B Garbage value

C Compilation error

D Random large number

💡 Hint

Global variables are automatically initialized in C.

Global variables in C are initialized to zero by default if not explicitly initialized.

❓ Predict Output

advanced

Output of multiple variable declarations and initializations

What is the output of this code?

C

int main() {
    int a = 5, b, c = 10;
    b = a + c;
    printf("%d %d %d", a, b, c);
    return 0;
}

A 5 0 10

B 5 15 10

C 5 10 10

D Compilation error

💡 Hint

Check the values assigned and used in the expression.

Variable a is 5, c is 10, b is assigned a + c = 15. So printing a, b, c outputs 5 15 10.

❓ Predict Output

advanced

Effect of missing initialization in array declaration

What will be the output of this program?

C

int main() {
    int arr[3];
    printf("%d", arr[0]);
    return 0;
}

A 0

B 1

C Garbage value (undefined behavior)

D Compilation error

💡 Hint

Local arrays without initialization contain garbage values.

Local arrays in C are not initialized automatically, so arr[0] contains garbage value.

🧠 Conceptual

expert

Number of initialized variables in mixed declarations

How many variables are initialized after this declaration?

C

int x = 1, y, z = 3, w;

A 2

B 3

C 4

D 1

💡 Hint

Count only variables with explicit initial values.

Only x and z are initialized explicitly; y and w are declared but uninitialized.