C language learning log 1.19

enumeration :

        Constant symbolization : Use symbols instead of specific numbers to represent numbers in programs .

         Enumeration is a user-defined data type , It uses keywords enum Declare with the following syntax :

                                       enum Enumeration type name { name 0,......., name n};

Enumeration type names are usually not really used , It's a name in braces , Because they are constant symbols , Their type is int, The values are from 0 To n. Such as :

                                        enum colers{red,yellow,green};

Three constants are created ,red The value of is 0,yellow The value of is 1, and green yes 2. When you need some constant values that can be arranged , The meaning of defining enumeration is to give these constant value names .

Enumeration of automatic counting :

#include<stdio.h>

enum COLOR{RED,YELLOW,GREEN,NumCOLORS};

int main()
{
    int color=-1;
    char *ColorNames[NumCOLORS] = {
        "red","yellow","green",
    };
    char *colorName = NULL;

    printf(" Enter the code of your favorite color :");
    scanf("%d",&color);
    if( color >=0&&color < NumCOLORS){
        colorName = ColorNames[color];
    }else{
        colorName="unknow";
    }
    printf(" Your favorite color is %s\n",colorName);
    return 0;
}

You can also specify values when declaring enumerators , for example :

        enum COLOR{RED=1,YELLOW,GREEN=5}; among YELLOW Namely 2 了 .

TIP: The values in the enumeration are const！！！