Types and Declarations

Variables must be defined in C before they are used. The declaration of a variable in C establishes the type of the object and its storage class.

Types

Integer

• three sizes: short int, int, and long int ("int" may be omitted);
• range of values implementation-dependent;
• signed, unsigned...

Floating Point

• three sizes: float, double and long double.
• range of values implementation-dependent;

Character

may also be signed or unsigned (default is implementation-dependent);

Void

By default functions return a value of type int; to specify that no value is returned use void.

Constants

e.g, const float pi = 3.141

Example

• See the char type illustration in Practical B.

Storage Classes

Storage class defines scope and lifetime of a variable.

Extern

Such variables are global; lifetime is the duration of the programme. Variables declared outside of any function have storage class extern.

Auto

Variables declared within a function have storage class auto --- they have scope local to the function; their lifetime is that of the invocation (call) of the function.

Static

The value of such a variable is preserved between successive calls to a function (scope: local).

Register

Used in programme optimisation...