C language elementary level (IX) enumeration

One . Constant symbolization

1.const

const double PI = 3.1415926;
//  week 
const int SUN  = 0;
const int MON  = 1;
const int TUES = 2;
const int WED  = 3;
const int THUR = 4;
const int FRI  = 5;
const int SAT  = 6;

2.#define

#define PI 3.1415926
//  week 
#define SUM  0
#define MON  1
#define TUES 2
#define WED  3
#define THUR 4
#define FRI  5
#define SAT  6

3. enumeration

 

Scope

#include <stdio.h>

void func (){
    #define N 12
    const int n = 12;    
}

int main(){
    printf("%d\n",N);
    //printf("%d\n",n);
}

Two . enumeration

1. What is it?

Enumeration is a user-defined data type , Enumeration can regard as Is a set of macro definitions .

2. How to use it?

enum  Enumeration type name { name 0, name 1, name 2,..., name n};

The names in the enumeration braces are constant symbols , The type is int, Value in turn from 0 To n.
Enumeration is to give these constant values , Specify a name .

Enumerators can be used directly as values .
Enumeration types can be used directly as types . 

#include <stdio.h>

enum Mouth{Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sept,Oct,Nov,Dec};
int month_days[]={31,28,31,30,31,30,31,31,30,31,30,31};
char* month_names[]={" January "," February "," March "," April "," May "," June "," July "," August "," September "," October "," November "," December "};

void PrintMonth(enum Mouth m){
    printf("%s Yes %d God \n",month_names[m],month_days[m]); 
}

void main(){
    enum Mouth m = Jan;
    PrintMonth(m);
}

  You can specify values when declaring enumerations

//  Commonly used system 
enum Radix{Bin=2,Oct=8,Dec=10,Hex=16};

You can also use one of these values , The following values are added successively 1

enum Mouth{Jan=1,Feb,Mar,Apr,May,Jun,Jul,Aug,Sept,Oct,Nov,Dec};