Enum declaration - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enum named Color.

C

enum [1] { RED, GREEN, BLUE };

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

AColors

Bcolor

CColor

DcolorEnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or plural forms for enum names.

Forgetting to name the enum.

The enum name should be Color to declare the enum properly.

2fill in blank

medium

Complete the code to declare an enum with explicit values.

C

enum Status { PENDING = [1], COMPLETED = 2, FAILED = 3 };

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

A2

B1

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning duplicate values to enum members.

Starting enum values at 2 when 1 is expected.

The first enum value is usually set to 1 here explicitly.

3fill in blank

hard

Fix the error in the enum declaration by completing the code.

C

enum [1] { LOW, MEDIUM, HIGH };

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APriorities

Bpriority

CPRIORITY

DPriority

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase enum names causing confusion.

Using plural or all uppercase names incorrectly.

The enum name should be Priority with capital P to follow naming conventions and avoid errors.

4fill in blank

hard

Fill both blanks to declare an enum and assign a value.

C

enum [1] { START = [2], STOP };

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AAction

B1

C0

DState

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural enum names.

Assigning 0 when 1 is expected.

The enum is named Action and START is assigned the value 1.

5fill in blank

hard

Fill all three blanks to declare an enum with custom values.

C

enum [1] { RED = [2], GREEN = [3] };

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

ATrafficLight

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as the first value when 1 is expected.

Using plural enum names.

The enum is named TrafficLight, with RED assigned 1 and GREEN assigned 2.

Practice

1. What is the main purpose of using enum in C programming?

easy

A. To declare a function prototype

B. To give names to a set of integer constants for better code readability

C. To create a new data type for floating-point numbers

D. To allocate memory dynamically

Solution

1. Step 1: Understand enum usage

   An enum is used to assign names to integer constants, making code easier to read and maintain.

2. Step 2: Compare other options

   Other options describe unrelated concepts: function prototypes, floating-point types, and memory allocation.

3. Final Answer:

   To give names to a set of integer constants for better code readability -> Option B

4. Quick Check:

   Enum = Named integer constants [OK]

Hint: Enums name numbers to make code clearer [OK]

Common Mistakes:

• Confusing enums with structs or unions
• Thinking enums allocate memory dynamically
• Assuming enums are for floating-point types

2. Which of the following is the correct syntax to declare an enum named Color with values RED, GREEN, and BLUE?

easy

A. enum Color { RED, GREEN, BLUE };

B. enum Color = { RED, GREEN, BLUE };

C. enum Color ( RED, GREEN, BLUE );

D. enum Color: RED, GREEN, BLUE;

Solution

1. Step 1: Recall enum declaration syntax

   The correct syntax uses curly braces to list values after the enum name without assignment or colons.

2. Step 2: Check each option

   enum Color { RED, GREEN, BLUE }; uses correct syntax: enum Color { RED, GREEN, BLUE };. Others use invalid symbols like '=', '(', or ':'.

3. Final Answer:

   enum Color { RED, GREEN, BLUE }; -> Option A

4. Quick Check:

   Enum syntax = enum Name { values } [OK]

Hint: Use curly braces and no equals sign in enum declaration [OK]

Common Mistakes:

• Using '=' instead of braces
• Using parentheses instead of braces
• Using colons after enum name

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

enum Day { SUN, MON, TUE = 5, WED, THU };
#include 
int main() {
    printf("%d %d %d %d %d", SUN, MON, TUE, WED, THU);
    return 0;
}

medium

A. 0 1 5 5 5

B. 0 1 2 3 4

C. 1 2 5 6 7

D. 0 1 5 6 7

Solution

1. Step 1: Understand enum value assignment

   By default, enum values start at 0 and increment by 1. Here, SUN=0, MON=1. TUE is explicitly set to 5.

2. Step 2: Calculate following values

   After TUE=5, WED becomes 6, and THU becomes 7 automatically.

3. Final Answer:

   0 1 5 6 7 -> Option D

4. Quick Check:

   Explicit enum value sets next values incrementally [OK]

Hint: Explicit enum value resets counting from that number [OK]

Common Mistakes:

• Assuming all values increment from zero ignoring explicit assignment
• Thinking WED and THU have same value as TUE
• Starting enum values from 1 by default

4. Identify the error in the following enum declaration:

enum Status {
    OK = 1,
    ERROR,
    WARNING = "2"
};

medium

A. ERROR must be assigned a value explicitly

B. Missing semicolon after enum declaration

C. Enum values must be integers, not strings

D. Enum names cannot be uppercase

Solution

1. Step 1: Check enum value types

   Enum values must be integer constants. Assigning a string like "2" is invalid.

2. Step 2: Verify other parts

   Semicolon is present, uppercase names are allowed, and ERROR can be auto-assigned after OK=1.

3. Final Answer:

   Enum values must be integers, not strings -> Option C

4. Quick Check:

   Enum values = integers only [OK]

Hint: Enum values must be integers, not strings [OK]

Common Mistakes:

• Using string literals as enum values
• Forgetting semicolon after enum
• Thinking enum names must be lowercase

5. Given the enum declaration:

enum Flags { FLAG_A = 1 << 0, FLAG_B = 1 << 1, FLAG_C = 1 << 2 };

int flags = FLAG_A | FLAG_C;

Which expression correctly checks if FLAG_B is set in flags?

hard

A. (flags & FLAG_B) != 0

B. (flags | FLAG_B) == 0

C. (flags & FLAG_B) == FLAG_B + 1

D. (flags ^ FLAG_B) == 0

Solution

1. Step 1: Understand bitwise flag checking

   To check if a flag is set, use bitwise AND and compare to zero.

2. Step 2: Analyze each option

   (flags & FLAG_B) != 0 correctly checks if FLAG_B bit is set by (flags & FLAG_B) != 0. Others use incorrect bitwise operations or comparisons.

3. Final Answer:

   (flags & FLAG_B) != 0 -> Option A

4. Quick Check:

   Bitwise AND with flag and compare to zero [OK]

Hint: Use bitwise AND and compare to zero to check flags [OK]

Common Mistakes:

• Using bitwise OR instead of AND for checking
• Comparing to wrong values
• Using XOR to check flags