C Language Enum (enum)

In this tutorial, you will learn about enum (enumeration) in C language programming through examples.

In C language programming, the enum type (also known as enum) is a data type composed of integer constants. To define an enum, the enum keyword will be used.

enum flag {const1, const2, ..., constN};

By default const1For 0, const2For1And so on. You can change the default value of enumeration elements during declaration if necessary.

//Change the default value of enumeration constants
enum suit {
　　　　club = 0,
　　　　diamonds =　10,
　　　　hearts =　20,
　　　　spades =　3,
};

Enumeration type declaration

When defining an enum type, a blueprint of the variable is created. Below, we will introduce how to create a variable of enum type.

enum boolean {false, true};
enum boolean check;　//　Declare an enumeration variable

Here, an enum boolean variable check will be created.

You can also declare enumeration variables like this.

enum boolean {false, true} check;

Here, the value of false is equal to 0, and the value of true is1.

Example: enumeration type

#include <stdio.h>
enum week {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday};
int main()
{
　　　　//Create a variable today of type enum week
　　　　enum week today;
　　　　today = Wednesday;
　　　　printf("Day %d", today+1);
　　　　return 0;
}

Output result

Day　4

Why use enumerations?

An enumeration variable can only take one value. This is an example instance of

#include <stdio.h>
enum suit {
　　　　club = 0,
　　　　diamonds =　10,
　　　　hearts =　20,
　　　　spades =　3
} card;
int main()　
{
　　　　card = club;
	printf("The size of enumeration variable = %d bytes", sizeof(card));	
	return 0;
}

Output result

The size of enumeration variable =　4　bytes

Here, we get4because the size of int is4bytes.

How to use enumerations for flags?

Let's take an example

enum designFlags {
	ITALICS =　1,
	BOLD =　2,
	UNDERLINE =　4
} button;

Suppose you are designing a button for a Windows application. You can set the flags ITALICS, BOLD, and UNDERLINE to handle text.

In the above pseudocode, all integral constants are2The reason for the power is

//in binary
ITALICS = 00000001
BOLD = 00000010
UNDERLINE = 00000100

Since the integral constant is2of powers, so you can combine two or more flags at once without usingbitwise OR |The operator for overlap. This allows you to select two or more flags at once. For example,

#include <stdio.h>
enum designFlags {
	BOLD =　1,
	ITALICS =　2,
	UNDERLINE =　4
};
int main() {
	int myDesign = BOLD | UNDERLINE;　
　　　　　　　　//　　　　00000001
　　　　　　　　//　　| 00000100
　　　　　　　　//　　___________
　　　　　　　　//　　　　00000101
	printf("%d", myDesign);
	return 0;
}

Output result

5

When the output is5You always know when bold and underline are used.

Additionally, you can add flags as needed.

if (myDesign & ITALICS) {
　　　　//Italic
}

Here, we have added italics in the design. Note that only italic code is written inside the if statement.

You do not need to use enums to complete almost all tasks in C language programming. However, they may be very convenient in some cases.