C++ Enum | Enumeration - Learn C++ - C++ Tutorial - C++ programming
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What is Enumeration in C++
- An enumeration is a user-defined data type that consists of integral constants. To define an enumeration, keyword enum is used.
enum season {spring, summer, autumn, winter };- Here, the name of the enumeration is season.
- And, spring, summer and winter are values of type season.
- By default, spring is 0, summer is 1 and so on. You can change the default value of an enum element during declaration (if necessary).
learn c++ tutorials - enum in c++ Example
enum season
{ spring = 0,
summer = 4,
autumn = 8,
winter = 12
};
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Enumerated Type Declaration
- When you create an enumerated type, only blueprint for the variable is created. Here's how you can create variables of enum type.
enum boolean { false, true };
// inside function
enum boolean check;- Here, a variable check of type enum boolean is created.
Here is another way to declare same check variable using different syntax.
enum boolean
{
false, true
} check;Example 1: Enumeration Type
#include <iostream>
using namespace std;
enum week {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday };
int main()
{
week today;
today = Wednesday;
cout << "Day " << today+1;
return 0;
}Output
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Example2: Changing Default Value of Enums
#include <iostream>
using namespace std;
enum seasons { spring = 34, summer = 4, autumn = 9, winter = 32};
int main() {
seasons s;
s = summer;
cout << "Summer = " << s << endl;
return 0;
}
Output
Summer = 4
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Why enums are used in C++ programming?
- An enum variable takes only one value out of many possible values.
Example to demonstrate it,
#include <iostream>
using namespace std;
enum suit {
club = 0,
diamonds = 10,
hearts = 20,
spades = 3
} card;
int main()
{
card = club;
cout << "Size of enum variable " << sizeof(card) << " bytes.";
return 0;
}
Output
Size of enum variable 4 bytes.- It's because the size of an integer is 4 bytes.;
- This makes enum a good choice to work with flags.
- You can accomplish the same task using C++ structures. However, working with enums gives you efficiency along with flexibility.
How to use enums for flags?
- Let us take an example,
enum designFlags {
ITALICS = 1,
BOLD = 2,
UNDERLINE = 4
} button;- Suppose you are designing a button for Windows application. You can set flags ITALICS, BOLD and UNDERLINE to work with text.
- There is a reason why all the integral constants are power of 2 in above pseudocode.
// In binary
ITALICS = 00000001
BOLD = 00000010
UNDERLINE = 00000100 - Since, the integral constants are power of 2, you can combine two or more flags at once without overlapping using bitwise OR | operator. This allows you to choose two or more flags at once.
For example,
#include <iostream>
using namespace std;
enum designFlags {
BOLD = 1,
ITALICS = 2,
UNDERLINE = 4
};
int main()
{
int myDesign = BOLD | UNDERLINE;
// 00000001
// | 00000100
// ___________
// 00000101
cout << myDesign;
return 0;
}
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Output
5- When the output is 5, you always know that bold and underline is used.
- Also, you can add flag to your requirements.
if (myDesign & ITALICS) {
// code for italics
}