在C語言中，列舉型別（enumerated type）宣告符號名稱來表示整形常量。使用enum關鍵字，可以建立一個新“型別”並指定它可具有的值，如：

//建立spectrum作標記名，那enum spectrum作為一個型別名使用
enum spectrum { red, orange, yellow, green, blue, violet};
//使color作為該型別的變數，red、yellow這些符號常量被稱為列舉符（enumerator）
enum spectrum color;

（1）enum常量
從技術上看，blue和red為int型常量，這裡在預設情況下，常量被賦予0,1,2等。其中,red = 0, orange = 1。
（2）賦值

//使用列舉型別的值
#include <stdio.h>
#include <string.h>	//提供strcmp()、strchr()函式原型
#include <stdbool.h> //C99特性
char * s_gets(char * st, int n);

enum spectrum { red, orange, yellow, green, blue, violet};
const char * colors [] = {"red"
 
, "orange", "yellow", "green", "blue", "violet"};
#define LEN 30

int main(void)
{
	char choice[LEN];
	enum spectrum color;
	bool color_is_found = false;
	
	puts("Enter a color (empty line to quit):");
	while (s_gets(choice, LEN) != NULL && choice[0] != '\0')
	{
		for (color = red; color <= violet;
 
 color++)
		{
			if (strcmp(choice, colors[color]) == 0)
			{
				color_is_found = true;
				break;
			}
		}
		if (color_is_found)
			switch (color)
		{
				case red: puts("Roses are red.");
					break;
				case orange: puts("Poppies are orange.");
					break;
				case yellow: puts("Sunflowers are yellow.");
					break;
				case green: puts("Roses are green.");
					break;
				case blue: puts("Bluebells are red.");
					break;
				case violet: puts("Violets are red.");
					break;
		}
		else
			printf("I dont know about the color %s.\n", choice);
		color_is_found = false;
		puts("Next color, please (empty line to quit):");
		
	}
	puts("Goodbye!");
	
	return 0;
}

char * s_gets(char * st, int n)
{
	char * ret_val;
	char * find;
	
	ret_val = fgets(st, n, stdin);
	if (ret_val)
	{
		find = strchr(st, '\n'); //查詢換行符
		if (find)					//如果地址不是NULL
			*find = '\0';			//在此處放置一個空字元
		else
			while (getchar() != '\n')
				continue;			//處理輸入行中剩餘的字串
				
	}
	return ret_val;
}

執行結果：