Why conditional logic is needed - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

C

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

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

Ax

Bnumber

Cvalue

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not declared or used in the code.

The variable x is used to check if it is greater than zero.

2fill in blank

medium

Complete the code to print "Even" if the number is divisible by 2.

C

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

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

Avalue

Bnumber

Cx

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable not declared or used in the code snippet.

The variable num is used to check divisibility by 2.

3fill in blank

hard

Fix the error in the condition 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 == only checks if age is exactly 18, not older.

The operator >= 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 < or > excludes boundary values.

The number must be greater than or equal to 10 and less than or equal to 20.

5fill in blank

hard

Fill all three blanks to print "Teenager" if age is between 13 and 19 inclusive.

C

if (age [1] 13 && age [2] 19 && age [3] 20) {
    printf("Teenager\n");
}

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

A>=

B<=

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators that exclude boundary ages.

The condition checks if age is at least 13, at most 19, and less than 20 (which is redundant but part of the exercise).

Practice

1. Why do we use conditional logic like if statements in C programs?

easy

A. To repeat code multiple times

B. To make decisions based on different conditions

C. To store multiple values in one variable

D. To define new data types

Solution

1. Step 1: Understand the purpose of conditional logic

   Conditional logic allows a program to choose different actions depending on conditions.

2. Step 2: Compare with other options

   Repeating code is done with loops, storing values uses arrays or variables, and defining types uses structs or typedefs.

3. Final Answer:

   To make decisions based on different conditions -> Option B

4. Quick Check:

   Conditional logic = decision making [OK]

Hint: If you want choices, use if-else [OK]

Common Mistakes:

• Confusing loops with conditionals
• Thinking variables store multiple values
• Mixing data types with logic

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

easy

A. if (condition) { /* code */ }

B. if condition { /* code */ }

C. if condition then { /* code */ }

D. if [condition] { /* code */ }

Solution

1. Step 1: Recall C syntax for if statements

   In C, conditions must be inside parentheses and code inside braces.

2. Step 2: Check each option

   if (condition) { /* code */ } matches the correct syntax: if (condition) { /* code */ }.

3. Final Answer:

   if (condition) { /* code */ } -> Option A

4. Quick Check:

   Parentheses around condition = correct syntax [OK]

Hint: Remember: if (condition) { } in C [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using square brackets instead of parentheses
• Adding 'then' keyword which C does not use

3. What will be the output of this C code?

int x = 10;
if (x > 5) {
    printf("Big\n");
} else {
    printf("Small\n");
}

medium

A. Compilation error

B. Small

C. No output

D. Big

Solution

1. Step 1: Evaluate the condition

   The variable x is 10, which is greater than 5, so the condition (x > 5) is true.

2. Step 2: Determine which branch runs

   Since the condition is true, the code inside the if block runs, printing "Big".

3. Final Answer:

   Big -> Option D

4. Quick Check:

   10 > 5 is true, so prints Big [OK]

Hint: Check condition true or false to pick output [OK]

Common Mistakes:

• Confusing which block runs on true
• Ignoring the newline character
• Thinking else block runs when condition is true

4. Find the error in this C code snippet:

int num = 7;
if num > 5 {
    printf("Yes\n");
} else {
    printf("No\n");
}

medium

A. Missing parentheses around the condition

B. Missing semicolon after if statement

C. Incorrect use of else keyword

D. Variable num not declared

Solution

1. Step 1: Check the if statement syntax

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

2. Step 2: Identify the error

   The code uses if num > 5 { ... } without parentheses, which is invalid syntax.

3. Final Answer:

   Missing parentheses around the condition -> Option A

4. Quick Check:

   If condition needs ( ) in C [OK]

Hint: Always put condition inside ( ) for if [OK]

Common Mistakes:

• Forgetting parentheses in if condition
• Adding semicolon after if line incorrectly
• Misplacing braces

5. You want to write a program that prints "Even" if a number is divisible by 2, and "Odd" otherwise. Which code snippet correctly uses conditional logic to do this?

hard

A. if (num % 2 != 0) {
printf("Even\n");
} else {
printf("Odd\n");
}

B. if (num / 2 == 0) {
printf("Even\n");
} else {
printf("Odd\n");
}

C. if (num % 2 == 0) {
printf("Even\n");
} else {
printf("Odd\n");
}

D. if (num % 2 = 0) {
printf("Even\n");
} else {
printf("Odd\n");
}

Solution

1. Step 1: Understand the condition for even numbers

   A number is even if dividing by 2 leaves remainder 0, checked by num % 2 == 0.

2. Step 2: Check each option's condition

   if (num % 2 == 0) { printf("Even\n"); } else { printf("Odd\n"); } correctly uses num % 2 == 0. if (num / 2 == 0) { printf("Even\n"); } else { printf("Odd\n"); } uses division instead of modulo. if (num % 2 = 0) { printf("Even\n"); } else { printf("Odd\n"); } uses assignment (=) instead of comparison (==). if (num % 2 != 0) { printf("Even\n"); } else { printf("Odd\n"); } reverses the logic.

3. Final Answer:

   if (num % 2 == 0) { printf("Even\n"); } else { printf("Odd\n"); } -> Option C

4. Quick Check:

   Modulo 2 equals 0 means even [OK]

Hint: Use modulo (%) to check divisibility [OK]

Common Mistakes:

• Using = instead of == in condition
• Using division instead of modulo
• Reversing if-else logic