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Symbolic Constants

We can define a symbolic constant at the top of the file 

#define SPEED_OF_LIGHT 299792458.0

Symbolic constants used to avoid burying "magic numbers" in the code

Symbolic constants make the code easier to understand and maintain 

#define NAME replacement_text

  • The compiler's pre-processor will replace all occurrences of name with replacement_text
  • it will not make the replacement if name is inside quotes ("…") or part of another name
Example:
The constants TRUE and FALSE are often used when a condition with logical value is wanted. They can be defined by: 

#define TRUE  1
#define FALSE 0