Why enumerations are used in C - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an enumeration for days of the week.

C

enum Days { Sunday, Monday, [1], Wednesday, Thursday, Friday, Saturday };

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

ATuesday

BMonth

CYear

DHour

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated terms like Month or Year instead of a day.

The enumeration for days of the week includes Tuesday as the third day.

2fill in blank

medium

Complete the code to assign a value to an enumeration constant.

C

enum Color { Red = 1, Green = 2, [1] = 3 };

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

AYellow

BOrange

CBlue

DPurple

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing colors not listed or unrelated terms.

The enumeration assigns Blue the value 3.

3fill in blank

hard

Fix the error in the enumeration declaration.

C

enum Status { Active, [1] 5, Pending };

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

AInactive =

BInactive

CInactive :

DInactive -

Attempts:

3 left

💡 Hint

Common Mistakes

Using ':' or '-' instead of '=' for assignment.

Enumeration constants must be assigned values using the '=' sign, so Inactive = is correct.

4fill in blank

hard

Fill both blanks to create an enumeration and use it in a variable declaration.

C

enum [1] { Low, Medium, High };
[2] priority;

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

APriority

Bint

Cenum Priority

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Using basic types like int or float instead of enum type.

The enum is named Priority, and the variable priority is declared with type enum Priority.

5fill in blank

hard

Fill all three blanks to define an enumeration and assign a value to a variable.

C

enum [1] { Red, Green, Blue };
enum [2] favoriteColor = [3];

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

AColor

CGreen

DBlue

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching enum names or assigning invalid values.

The enum is named Color, the variable favoriteColor is declared as enum Color, and assigned the value Green.

Practice

1. Why are enumerations (enums) used in C programming?

easy

A. To give meaningful names to a set of related integer constants

B. To create floating-point variables

C. To allocate memory dynamically

D. To perform input/output operations

Solution

1. Step 1: Understand the purpose of enums

   Enums assign names to integer values, making code easier to read and maintain.

2. Step 2: Compare with other options

   Options B, C, and D describe unrelated tasks like floating-point variables, memory allocation, and I/O operations.

3. Final Answer:

   To give meaningful names to a set of related integer constants -> Option A

4. Quick Check:

   Enums = Named integer constants [OK]

Hint: Enums name numbers for clarity and safety [OK]

Common Mistakes:

• Thinking enums create new data types like floats
• Confusing enums with memory management
• Assuming enums handle input/output

2. Which of the following is the correct way to declare an enumeration in C?

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

   In C, enums are declared using the syntax: enum Name { list_of_constants };

2. Step 2: Check each option

   enum Color { RED, GREEN, BLUE }; matches the correct syntax. Options B, C, and D use invalid assignment or brackets.

3. Final Answer:

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

4. Quick Check:

   Correct enum syntax uses braces {} [OK]

Hint: Use braces {} to list enum values [OK]

Common Mistakes:

• Using = instead of braces
• Using parentheses or brackets instead of braces
• Missing semicolon at the end

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

enum Day { MON=1, TUE, WED };
int main() {
    enum Day today = TUE;
    printf("%d", today);
    return 0;
}

medium

A. 0

B. 2

C. 1

D. 3

Solution

1. Step 1: Understand enum value assignment

   MON is assigned 1 explicitly, so TUE becomes 2, WED becomes 3 automatically.

2. Step 2: Identify the value of 'today'

   Variable today is set to TUE, which has the value 2.

3. Final Answer:

   2 -> Option B

4. Quick Check:

   Enum auto-increments from assigned start [OK]

Hint: Enum values auto-increment unless set [OK]

Common Mistakes:

• Assuming enum starts at 0 when explicitly set
• Confusing enum names with values
• Forgetting auto-increment behavior

4. Identify the error in this enum declaration:

enum Status {
    OK = 0,
    ERROR = 1,
    UNKNOWN = 1
};

medium

A. Duplicate enum values are not allowed

B. Enum values must start from 0

C. No error, this is valid code

D. Enum names cannot be uppercase

Solution

1. Step 1: Check enum value rules

   In C, enum values can be duplicated; it's allowed to have multiple names with the same value.

2. Step 2: Verify other options

   Enum values do not have to start at 0, and names can be uppercase. So no syntax error here.

3. Final Answer:

   No error, this is valid code -> Option C

4. Quick Check:

   Duplicate enum values allowed [OK]

Hint: Duplicate enum values are allowed in C [OK]

Common Mistakes:

• Thinking duplicate values cause errors
• Assuming enum must start at zero
• Believing enum names must be lowercase

5. You want to use an enum to represent traffic light colors with values RED=0, YELLOW=5, GREEN=10. Which enum declaration correctly achieves this?

hard

A. enum TrafficLight { RED=0, YELLOW, GREEN=10 };

B. enum TrafficLight { RED=1, YELLOW=5, GREEN=10 };

C. enum TrafficLight { RED=0, YELLOW=5, GREEN };

D. enum TrafficLight { RED=0, YELLOW=5, GREEN=10 };

Solution

1. Step 1: Assign explicit values to enum members

   To get RED=0, YELLOW=5, GREEN=10, each must be assigned explicitly.

2. Step 2: Analyze each option

   enum TrafficLight { RED=0, YELLOW=5, GREEN=10 }; assigns all values explicitly. enum TrafficLight { RED=1, YELLOW=5, GREEN=10 }; assigns RED=1 (not 0), YELLOW=5, GREEN=10. enum TrafficLight { RED=0, YELLOW, GREEN=10 }; assigns RED=0, YELLOW unassigned (would be 1), GREEN=10. enum TrafficLight { RED=0, YELLOW=5, GREEN }; assigns RED=0, YELLOW=5, but GREEN unassigned (would be 6).

3. Final Answer:

   enum TrafficLight { RED=0, YELLOW=5, GREEN=10 }; -> Option D

4. Quick Check:

   Explicit values ensure correct enum numbers [OK]

Hint: Assign all enum values explicitly for specific numbers [OK]

Common Mistakes:

• Assuming unassigned enums auto-skip to next explicit value
• Forgetting to assign all values explicitly
• Expecting enums to auto-increment from last explicit value