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Digression – Symbolic Constants in C

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). Specifying Symbolic Constants in C.

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Digression – Symbolic Constants in C

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

  2. Specifying Symbolic Constants in C • Two ways • Textual substitution • Declaration of const data object Symbolic Constants in C

  3. A preprocessor directive! Constant – Textual Substitution • See page • 14 & 89 in K&R • 215 in D&D #define NAME replacement-text • E.g., #define PI 3.14159265358979323846 #define LOWER 0#define UPPER 300#define STEP 20 It is traditional in C for textual substitution names to be all UPPER CASE Symbolic Constants in C

  4. Constant – Textual Substitution • See page 14 & 89 in K&R #define NAME replacement-text • E.g., #define PI 3.14159265358979323846 #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 C

  5. Constant Declaration const double pi = 3.14159265358979323846; const double c = 2.99792458e+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 Symbolic Constants in C

  6. Questions? Next Topic Symbolic Constants in C

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