1. Symbolic Constants in CCS-2303, C-Term 20101 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)

2. Symbolic Constants in CCS-2303, C-Term 20102 Specifying Symbolic Constants in C Two ways –Textual substitution –Declaration of const data object

3. Symbolic Constants in CCS-2303, C-Term 20103 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 A preprocessor directive!

4. Symbolic Constants in CCS-2303, C-Term 20104 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

5. Symbolic Constants in CCS-2303, C-Term 20105 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

6. Symbolic Constants in CCS-2303, C-Term 20106 Questions? Next Topic