Relational operators in C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to compare if a is greater than b.

C

if (a [1] b) {
    printf("a is greater than b\n");
}

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

A>

B<

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>'

Using '==' which checks equality, not greater than

The '>' operator checks if the left value is greater than the right value.

2fill in blank

medium

Complete the code to check if x is not equal to y.

C

if (x [1] y) {
    printf("x and y are different\n");
}

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

A!=

B==

C>=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which checks equality, not difference

Using '>=' or '<=' which are relational but not for inequality

The '!=' operator checks if two values are not equal.

3fill in blank

hard

Fix the error in the condition to check if num is less than or equal to 100.

C

if (num [1] 100) {
    printf("num is 100 or less\n");
}

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

A==

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' which excludes 100

Using '==' which only checks equality

The '<=' operator checks if the left value is less than or equal to the right value.

4fill in blank

hard

Fill both blanks to create a condition that checks if value is between 10 and 20 inclusive.

C

if (value [1] 10 && value [2] 20) {
    printf("value is between 10 and 20\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

Using '>' instead of '>=' excludes 10

The condition uses '>=' to check value is at least 10, and '<=' to check it is at most 20.

5fill in blank

hard

Fill all three blanks to create a condition that checks if score is greater than 50 and less than 100.

C

if (score [1] 50 && score [2] 100 && score [3] 75) {
    printf("score is between 51 and 99 and greater than 75\n");
}

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

A>=

B<

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>=' instead of '>' includes 50 which is not desired

Using '<=' instead of '<' includes 100 which is not desired

Using '<' instead of '>' for the last condition

The first '{{BLANK_1}}' uses '>' to check score is more than 50 (not equal). The second '{{BLANK_2}}' uses '<' to check score is less than 100. The third '{{BLANK_3}}' uses '>' to check score is greater than 75.

Practice

1. Which of the following relational operators in C checks if two values are equal?

easy

A. !=

B. ==

C. =

D. >

Solution

1. Step 1: Understand the purpose of each operator

   The operator == is used to compare two values for equality. The single = is an assignment operator, != checks inequality, and > checks if left is greater than right.

2. Step 2: Identify the equality operator

   Since == compares two values for equality, it is the correct relational operator for this purpose.

3. Final Answer:

   == -> Option B

4. Quick Check:

   Equality check = == [OK]

Hint: Equality uses double equals ==, not single = [OK]

Common Mistakes:

• Confusing = (assignment) with == (equality)
• Using != instead of ==
• Using > instead of ==

2. Which of the following is the correct syntax to check if variable a is not equal to variable b in C?

easy

A. a !== b

B. a <> b

C. a =! b

D. a != b

Solution

1. Step 1: Recall the correct not equal operator in C

   In C, the operator for not equal is !=. Other options like <> or !== are not valid in C.

2. Step 2: Verify the syntax correctness

   The expression a != b correctly compares if a is not equal to b.

3. Final Answer:

   a != b -> Option D

4. Quick Check:

   Not equal operator = != [OK]

Hint: Use != for not equal in C, not <> or !== [OK]

Common Mistakes:

• Using <> which is invalid in C
• Writing =! instead of !=
• Using !== which is from other languages

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

int a = 5, b = 10;
if (a > b) {
    printf("True\n");
} else {
    printf("False\n");
}

medium

A. True

B. 5

C. False

D. 10

Solution

1. Step 1: Evaluate the relational expression a > b

   Variable a is 5 and b is 10. Since 5 is not greater than 10, the expression a > b is false.

2. Step 2: Determine which branch executes

   Because the condition is false, the else block runs, printing "False".

3. Final Answer:

   False -> Option C

4. Quick Check:

   5 > 10 = false [OK]

Hint: Compare values carefully; 5 > 10 is false [OK]

Common Mistakes:

• Assuming 5 > 10 is true
• Confusing else and if blocks
• Ignoring relational operator meaning

4. Identify the error in the following C code snippet:

int x = 7, y = 3;
if (x =< y) {
    printf("x is less or equal to y\n");
}

medium

A. Using =< instead of <=

B. Missing semicolon after if condition

C. Using assignment operator inside if

D. Incorrect printf syntax

Solution

1. Step 1: Check the relational operator syntax

   The operator =< is invalid in C. The correct operator for less than or equal is <=.

2. Step 2: Confirm other syntax correctness

   The semicolon after if condition is not needed, assignment operator is not used here, and printf syntax is correct.

3. Final Answer:

   Using =< instead of <= -> Option A

4. Quick Check:

   Less or equal operator is <=, not =< [OK]

Hint: Remember <= for less or equal, not =< [OK]

Common Mistakes:

• Swapping <= to =<
• Adding semicolon after if condition
• Confusing assignment = with comparison ==

5. Given the code below, what will be the output?

int a = 4, b = 4, c = 5;
if (a == b && b < c) {
    printf("Yes\n");
} else {
    printf("No\n");
}

Choose the correct output considering relational operators combined with logical operators.

hard

A. Yes

B. No

C. 4

D. Syntax Error

Solution

1. Step 1: Evaluate the first condition a == b

   Both a and b are 4, so a == b is true.

2. Step 2: Evaluate the second condition b < c

   b is 4 and c is 5, so b < c is true.

3. Step 3: Combine conditions with logical AND

   Both conditions are true, so the combined condition is true, executing the if block.

4. Final Answer:

   Yes -> Option A

5. Quick Check:

   (4 == 4) && (4 < 5) = true [OK]

Hint: Both conditions must be true for && to print Yes [OK]

Common Mistakes:

• Ignoring logical AND meaning
• Mixing up == and =
• Assuming false when both conditions true