If statement in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested if statements

What is the output of this C code snippet?

C

#include <stdio.h>

int main() {
    int x = 5;
    if (x > 3) {
        if (x < 10) {
            printf("Inside nested if\n");
        }
    } else {
        printf("Outside if\n");
    }
    return 0;
}

A Inside nested if

B Outside if

C No output

D Compilation error

💡 Hint

Check the conditions in the nested if statements carefully.

Since x is 5, it is greater than 3 and less than 10, so the nested if block runs and prints "Inside nested if".

❓ Predict Output

intermediate

Output of if-else with logical operators

What will this program print?

C

#include <stdio.h>

int main() {
    int a = 4, b = 7;
    if (a > 3 && b < 10) {
        printf("Condition met\n");
    } else {
        printf("Condition not met\n");
    }
    return 0;
}

A Condition met

B Condition not met

C Compilation error

D No output

💡 Hint

Both parts of the && operator must be true for the if block to run.

a is 4 (greater than 3) and b is 7 (less than 10), so the condition is true and "Condition met" is printed.

❓ Predict Output

advanced

Output of if statement with assignment inside condition

What is the output of this program?

C

#include <stdio.h>

int main() {
    int x = 0;
    if (x = 5) {
        printf("x is %d\n", x);
    } else {
        printf("x is zero\n");
    }
    return 0;
}

A x is zero

B x is 5

C Compilation error

D No output

💡 Hint

Remember that assignment inside if condition returns the assigned value.

The assignment x = 5 sets x to 5 and returns 5, which is true, so the if block runs and prints "x is 5".

❓ Predict Output

advanced

Output of if statement with missing braces

What will this program print?

C

#include <stdio.h>

int main() {
    int n = 2;
    if (n > 1)
        printf("Greater than one\n");
    printf("Always printed\n");
    return 0;
}

A Compilation error

B Always printed

C Greater than one

D Greater than one\nAlways printed

💡 Hint

Without braces, only the first statement is controlled by if.

Only the first printf is inside the if. The second printf runs always. So both lines print.

🧠 Conceptual

expert

Behavior of if statement with uninitialized variable

What happens when you run this code?

C

#include <stdio.h>

int main() {
    int x;
    if (x) {
        printf("x is true\n");
    } else {
        printf("x is false\n");
    }
    return 0;
}

A Always prints "x is true"

B Always prints "x is false"

C Undefined behavior due to uninitialized variable x

D Compilation error

💡 Hint

Local variables without initialization have unpredictable values.

Variable x is uninitialized, so its value is garbage. Using it in if condition causes undefined behavior.

Practice

1. What does an if statement do in C programming?

easy

A. It stores data in memory.

B. It repeats code multiple times.

C. It runs code only if a condition is true.

D. It defines a new function.

Solution

1. Step 1: Understand the purpose of an if statement

   An if statement checks a condition and decides whether to run the code inside it.

2. Step 2: Compare options with the if statement behavior

   Only It runs code only if a condition is true. correctly describes that the code runs only if the condition is true.

3. Final Answer:

   It runs code only if a condition is true. -> Option C

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If condition true, run code inside braces [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if stores data
• Mixing if with function definition

2. Which of the following is the correct syntax for an if statement in C?

easy

A. if (condition) { printf("Hello"); }

B. if (condition) printf("Hello")

C. if condition: printf("Hello");

D. if condition { printf("Hello"); }

Solution

1. Step 1: Recall correct if statement syntax in C

   The condition must be inside parentheses, and the code block inside braces.

2. Step 2: Check each option

   if (condition) { printf("Hello"); } uses parentheses for condition and braces for code block, which is correct syntax.

3. Final Answer:

   if (condition) { printf("Hello"); } -> Option A

4. Quick Check:

   Parentheses + braces = correct if syntax [OK]

Hint: Use parentheses for condition and braces for code block [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using colon instead of braces
• Missing semicolon after printf

3. What will be the output of this code?

int x = 5;
if (x > 3) {
    printf("Yes");
} else {
    printf("No");
}

medium

A. Yes

B. No

C. Error

D. No output

Solution

1. Step 1: Evaluate the condition x > 3

   Since x is 5, 5 > 3 is true.

2. Step 2: Determine which block runs

   The if block runs and prints "Yes" because the condition is true.

3. Final Answer:

   Yes -> Option A

4. Quick Check:

   5 > 3 is true, prints Yes [OK]

Hint: If condition true, prints inside if block [OK]

Common Mistakes:

• Confusing else block execution
• Assuming syntax error without checking code
• Ignoring condition evaluation

4. Find the error in this code snippet:

int a = 10;
if a > 5 {
    printf("Big");
}

medium

A. Variable a is not declared

B. Missing semicolon after printf

C. Braces should be parentheses

D. Condition must be inside parentheses

Solution

1. Step 1: Check if statement syntax

   The condition in an if statement must be inside parentheses in C.

2. Step 2: Identify the error in the code

   The code has if a > 5 { ... } without parentheses around a > 5, which is incorrect.

3. Final Answer:

   Condition must be inside parentheses -> Option D

4. Quick Check:

   Condition needs parentheses [OK]

Hint: Always put condition inside parentheses [OK]

Common Mistakes:

• Using braces instead of parentheses for condition
• Forgetting semicolon after statements
• Assuming variable not declared

5. Consider this code:

int n = 0;
if (n) {
    printf("True");
} else {
    printf("False");
}

What will be printed and why?

hard

A. True, because n is zero

B. False, because zero is false in C

C. Error, n must be boolean

D. No output, program crashes

Solution

1. Step 1: Understand how C treats integers in conditions

   In C, zero means false, any nonzero means true.

2. Step 2: Evaluate the condition if (n)

   Since n is 0, the condition is false, so else block runs.

3. Step 3: Determine output

   The else block prints "False".

4. Final Answer:

   False, because zero is false in C -> Option B

5. Quick Check:

   Zero = false, prints False [OK]

Hint: Zero means false, nonzero means true in if conditions [OK]

Common Mistakes:

• Thinking zero is true
• Expecting boolean type only
• Assuming program error