If statement in C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the number is positive.

C

if (num [1] 0) {
    printf("Positive number\n");
}

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

A>

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' will check for negative numbers.

Using '==' checks for equality, not positivity.

The condition num > 0 checks if the number is positive.

2fill in blank

medium

Complete the code to print "Even" if the number is even.

C

if (num % 2 [1] 0) {
    printf("Even\n");
}

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

A>

B==

C!=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' will check for odd numbers instead.

Using '>' or '<' does not correctly check for evenness.

The condition num % 2 == 0 checks if the number is even.

3fill in blank

hard

Fix the error in the if statement to check if age is at least 18.

C

if (age [1] 18) {
    printf("Adult\n");
}

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

A==

B<=

C>=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '<=' checks for younger ages.

Using '==' only checks if age is exactly 18.

The condition age >= 18 checks if age is 18 or older.

4fill in blank

hard

Fill both blanks to check if a number is between 10 and 20 (inclusive).

C

if (num [1] 10 && num [2] 20) {
    printf("In range\n");
}

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

A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '<=' excludes 20 from the range.

Using '>' instead of '>=' excludes 10 from the range.

The condition checks if num >= 10 and num <= 20, meaning num is between 10 and 20 inclusive.

5fill in blank

hard

Fill all three blanks to print "Valid" if score is above 50 and below 100.

C

if (score [1] 50 && score [2] 100) {
    printf("[3]\n");
}

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

A>

B<

C<=

DValid

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' or '<=' changes the range to include 50 or 100.

Printing wrong message or missing quotes.

The condition checks if score > 50 and score < 100. If true, it prints "Valid".

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