Digression

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)

2
Specifying Symbolic Constants in C

• Two ways
• Textual substitution
• Declaration of const data object

3
Constant Textual Substitution

• See page
• 14 89 in KR
• 215 in DD
• define NAME replacement-text
• E.g.,
• define PI 3.14159265358979323846
• define LOWER 0define UPPER 300define STEP 20

It is traditional in C for textual substitution
names to be all UPPER CASE
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Constant Textual Substitution

• See page 14 89 in KR
• define NAME replacement-text
• E.g.,
• define PI 3.14159265358979323846
• define LOWER 0define UPPER 300define STEP 20

When a textual substitution constant is used in a
program, the compiler simply substitutes the
replacement text on the fly
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Constant Declaration

• const double pi 3.14159265358979323846
• const double c 2.99792458e8 / 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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Questions?

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