Enumerated Data Types

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Enumerated Data Types
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Enumerated Data Types

• representing series of values

• E.g. Simulate a traffic light system

• Require three values to represent red, yellow,
  and green

• No built-in C color data type

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Solution 1

• Use integer values to represent colors

• E.g. red 0, yellow 1, and green 2

• Source code is not readable

• For example,
• x 1
• What does this do assign the number one or the
  color yellow to x?

• Error prone

• mistakenly use wrong number for a color

• updating is also difficult

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Solution 2

• Use names instead of numbers

• Create named constants for each of the values

• const int RED 0
• const int YELLOW 1
• const int GREEN 2

• Easy to distinguish b/w integers and colors

• int y 1 // assigns the integer one
• int x YELLOW // assigns yellow

• Still x is declared as int

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Enum provides a solution

• C uses the enum statement

• to assign sequential integer values to names

• provide a type name for declaration

• E.g.
• Enum TraficLightColor Red, Yellow, Green
• int y
• TraficlightColor x
• y 1
• x Yellow

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