typedef enum {
RESET = 0,
SET = !RESET
} FlagStatus, ITStatus;
This sentence means to alias enum {reset = 0, set =! Reset}: FlagStatus and ITStatus
The FlagStatus and ITStatus that appear after this can be regarded as enum {reset = 0, set =! Reset}
The purpose of this is to save code, improve readability, and be easy to maintain~
1. Define a new data type - enumeration type
The following code defines this new data type - enumeration
enum DAY
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
};
(1) An enumeration is a collection in which the elements (enumeration members) are named integer constants separated by commas.
(2) DAY is an identifier, which can be regarded as the name of this collection. It is an optional option, that is, it can be written without writing.
(3) If the value of the first enumeration member is not assigned, the default value is integer 0, and the value of subsequent enumeration members is added with 1 to the previous member. That is, the TUE value in the above code is 2.
(4) You can think of setting the value of enumeration members to customize integers in a range.
(5) Enumeration type is an alternative to preprocessing instruction #define.
(6) Semicolon is used for type definition; end.
2. Use enumeration type to declare variables
Common basic data types are
Integer int, single precision floating-point float, double precision floating-point double, character char, short integer short. These basic data types usually declare variables as follows:
char a; // The type of variable a is char int x,y,z;//Variables x, y, z are of type int double m,n;//The type of the variable resul is double precision floating-point double
Enumerative types and methods are defined separately
enum DAY
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
};
enum DAY today;//The variable today type is enum DAY
enum DAY good_day,bad_day;//Variable good_day and bad_ The type of day is enum DAY
Method 2: type definition and variable declaration are carried out at the same time
enum //DAY is omitted here
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
}workday;//The type of the variable workday is enum DAY
enum BOOLEAN
{
false,
true
}end_flag,match_flag;//Defines an enumeration type and declares two enumeration variables
Method 3: use the typedef keyword to define the enumeration type as an alias, and use the alias to declare variables
typedef enum workday
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
}workday; //Workday here is the alias of enum workday
workday today, tomorrow; //The types of variables today and tomorrow are enumerative workday, i.e. enum workday
It can also be expressed like this
typedef enum
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
}workday; //Workday here is the alias of enum workday
workday today, tomorrow; //The types of variables today and tomorrow are enumerative workday, i.e. enum workday
Or this expression
typedef enum workday
{
MON = 1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
};
workday today, tomorrow; //The types of variables today and tomorrow are enumerative workday, i.e. enum workday
Error declaration
Note: enumeration types with the same name cannot be defined in the same program, and named constants with the same name cannot exist in different enumeration types. Examples of errors are as follows:
Error declaration 1: there is an enumeration type with the same name
typedef enum
{
wednesday,
thursday,
friday
} workday;
typedef enum WEEK
{
saturday,
sunday = 0,
monday,
} workday;
Error declaration 2: there is an enumeration member with the same name
typedef enum
{
wednesday,
thursday,
friday
} workday_1;
typedef enum WEEK
{
wednesday,
sunday = 0,
monday,
} workday_2;
3. Use variables of enumeration type
3.1 assign values to enumerated variables.
The example compares the assignment of enumeration type with that of basic data type:
Method 1: declare the variable first, and then assign a value to the variable
#include<stdio.h>
enum DAY
{
MON=1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
};
void main()
{
int x, y, z;
x = 10;
y = 20;
z = 30;
enum DAY yesterday, today, tomorrow;
yesterday = MON;
today = TUE;
tomorrow = WED;
printf("%d %d %d \n", yesterday, today, tomorrow);
}
Method 2: declare variables and assign initial values at the same time
#include <</SPAN>stdio.h>
enum DAY { MON=1, TUE, WED, THU, FRI, SAT, SUN };
void main()
{
int x=10, y=20, z=30;
enum DAY yesterday = MON,
today = TUE,
tomorrow = WED;
printf("%d %d %d \n", yesterday, today, tomorrow);
}
Method 3: declare variables while defining types, and then assign values to variables.
#include <stdio.h>
enum DAY { MON=1, TUE, WED, THU, FRI, SAT, SUN } yesterday, today, tomorrow;
int x, y, z;
void main()
{
x = 10; y = 20; z = 30;
yesterday = MON;
today = TUE;
tomorrow = WED;
printf("%d %d %d \n", x, y, z); //Output: 10 20 30
printf("%d %d %d \n", yesterday, today, tomorrow); //Output: 1 2 3
}
Method 4: type definition, variable declaration and initial value assignment are carried out at the same time.
#include <</SPAN>stdio.h>
enum DAY
{
MON=1,
TUE,
WED,
THU,
FRI,
SAT,
SUN
}
yesterday = MON, today = TUE, tomorrow = WED;
int x = 10, y = 20, z = 30;
void main()
{
printf("%d %d %d \n", x, y, z); //Output: 10 20 30
printf("%d %d %d \n", yesterday, today, tomorrow); //Output: 1 2 3
}
3.2 when assigning integer values to enumerated variables, type conversion is required.
#include <stdio.h>
enum DAY { MON=1, TUE, WED, THU, FRI, SAT, SUN };
void main()
{
enum DAY yesterday, today, tomorrow;
yesterday = TUE;
today = (enum DAY) (yesterday + 1); //Type conversion
tomorrow = (enum DAY) 30; //Type conversion
//tomorrow = 3; // error
printf("%d %d %d \n", yesterday, today, tomorrow); //Output: 2 3 30
}
3.3 using enumerated variables
#include<</SPAN>stdio.h>
enum
{
BELL = '\a',
BACKSPACE = '\b',
HTAB = '\t',
RETURN = '\r',
NEWLINE = '\n',
VTAB = '\v',
SPACE = ' '
};
enum BOOLEAN { FALSE = 0, TRUE } match_flag;
void main()
{
int index = 0;
int count_of_letter = 0;
int count_of_space = 0;
char str[] = "I'm Ely efod";
match_flag = FALSE;
for(; str[index] != '\0'; index++)
if( SPACE != str[index] )
count_of_letter++;
else
{
match_flag = (enum BOOLEAN) 1;
count_of_space++;
}
printf("%s %d times %c", match_flag ? "match" : "not match", count_of_space, NEWLINE);
printf("count of letters: %d %c%c", count_of_letter, NEWLINE, RETURN);
}
Output:
match 2 times count of letters: 10 Press any key to continue
- Enumeration type and sizeof operator
#include<stdio.h>
enum escapes
{
BELL = '\a',
BACKSPACE = '\b',
HTAB = '\t',
RETURN = '\r',
NEWLINE = '\n',
VTAB = '\v',
SPACE = ' '
};
enum BOOLEAN { FALSE = 0, TRUE } match_flag;
void main()
{
printf("%d bytes \n", sizeof(enum escapes)); //4 bytes
printf("%d bytes \n", sizeof(escapes)); //4 bytes
printf("%d bytes \n", sizeof(enum BOOLEAN)); //4 bytes
printf("%d bytes \n", sizeof(BOOLEAN)); //4 bytes
printf("%d bytes \n", sizeof(match_flag)); //4 bytes
printf("%d bytes \n", sizeof(SPACE)); //4 bytes
printf("%d bytes \n", sizeof(NEWLINE)); //4 bytes
printf("%d bytes \n", sizeof(FALSE)); //4 bytes
printf("%d bytes \n", sizeof(0)); //4 bytes
}
- Comprehensive examples
#include<</SPAN>stdio.h>
enum Season //Note that if you put it below, you can't directly declare it later
{
spring, summer=100, fall=96, winter
};
typedef enum
{
Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
}
Weekday;
void main()
{
printf("%d \n", spring); // 0
printf("%d, %c \n", summer, summer); // 100, d
printf("%d \n", fall+winter); // 193
Season mySeason=winter; //That's it. According to the above definition, you can also enum Season mySeason
if(winter==mySeason)
printf("mySeason is winter \n"); // mySeason is winter
int x=100;
if(x==summer)
printf("x is equal to summer\n"); // x is equal to summer
printf("%d bytes\n", sizeof(spring)); // 4 bytes
printf("sizeof Weekday is: %d \n", sizeof(Weekday)); //sizeof Weekday is: 4
Weekday today = Saturday;
Weekday tomorrow;
if(today == Monday)
tomorrow = Tuesday;
else
tomorrow = (Weekday) (today + 1); //remember to convert from int to Weekday
}
This article draws on the article of CSDN blogger "ppaiml", and the original link is: https://blog.csdn.net/yuantuo3887/article/details/79211313