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An introduction to dealing with constants in C
In the last post I introduced variables in C.
In this post I want to tell you everything about constants in C.
A constant is declared similarly to variables, except it is prepended with the
const keyword, and you always need to specify a value.
const int age = 37;
This is perfectly valid C, although it is common to declare constants uppercase, like this:
const int AGE = 37;
It’s just a convention, but one that can greatly help you while reading or writing a C program as it improves readability. Uppercase name means constant, lowercase name means variable.
A constant name follows the same rules for variable names: can contain any uppercase or lowercase letter, can contain digits and the underscore character, but it can’t start with a digit.
Age10 are valid variable names,
1AGE is not.
Another way to define constants is by using this syntax:
#define AGE 37
In this case, you don’t need to add a type, and you don’t also need the
= equal sign, and you omit the semicolon at the end.
The C compiler will infer the type from the value specified, at compile time.