Symbolic Constants in CCS-2303, C-Term Digression – Symbolic Constants in C CS-2303, System Programming Concepts (Slides include materials from The C Programming Language, 2 nd edition, by Kernighan and Ritchie and from C: How to Program, 5 th and 6 th editions, by Deitel and Deitel)

Symbolic Constants in CCS-2303, C-Term Specifying Symbolic Constants in C Two ways –Textual substitution –Declaration of const data object

Symbolic Constants in CCS-2303, C-Term Constant – Textual Substitution See page 14 & 89 in K&R 215 in D&D #define NAME replacement-text E.g., #define PI #define LOWER 0 #define UPPER 300 #define STEP 20 It is traditional in C for textual substitution names to be all UPPER CASE A preprocessor directive!

Symbolic Constants in CCS-2303, C-Term Constant – Textual Substitution See page 14 & 89 in K&R #define NAME replacement-text E.g., #define PI #define LOWER 0 #define UPPER 300 #define STEP 20 When a textual substitution constant is used in a program, the compiler simply substitutes the replacement text on the fly

Symbolic Constants in CCS-2303, C-Term Constant Declaration const double pi = ; const double c = e+8; /* speed of light in meters/sec */ Defines a value of the declared type with the declared name I.e., creates storage to hold this value Must be initialized May never be left side of an assignment

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