C programming enumeration

C programming enumeration

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  • An enumerationis a user-defined data type that consists of integral constants. To define an enumeration, keyword enum is used. • enum flag { const1, const2, ..., constN }; • Here, name of the enumeration is flag. • And, const1, const2,...., constN are values of type flag. • By default, const1 is 0, const2 is 1 and so on. You can change default values of enum elements during declaration (if necessary). • // Changing default values of enum • enum suit { club = 0, diamonds = 10, hearts = 20, spades = 3 }; 2
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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 }; 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; 3
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  Example: Enumeration Type 4
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  Why enums areused in C programming? • Enum variable takes only one value out of many possible values. Example to demonstrate it, This makes enum a good choice to work with flags. 5
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  • It's becausethe size of an integer is 4 bytes. • This makes enum a good choice to work with flags. • You can accomplish the same task using structures. However, working with enums gives you efficiency along with flexibility. 6
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  How to useenums for flags? • Suppose you are designing a button for Windows application. You can set flags ITALICS, BOLD and UNDERLINE to work with text. • here is a reason why all the integral constants are power of 2 in above pseudocode. 7
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  • Since, theintegral 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, 8
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  • When theoutput is 5, you always know that bold and underline is used. • Also, you can add flag to your requirements. 9
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