Semiconductor & Computer Engineering
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Revision as of 18:57, 13 December 2013
The meaning of a value stored in an object is determined solely by the type of the expression used to access it - for example the type used in the variable declaration. There are two categories of types:
- object types - types used to describe objects
- function types - types used to describe functions
Additionally an object may have a complete or incomplete type. An incomplete type is a type that describes an object but lacks information needed to determine its size. For example: an array of unknown size or struct or union types whose members were not specified. A complete type is a type that describes an object with sufficient information needed to determine its size.
Basic Types
Basic types are the fundamental building blocks of all C programs. All basic types are complete types. Basic types are divided into four sub-categories: char type, signed integer types, unsigned integer types, and floating types.
Character Types
There are three distinct character types: char, signed char, and unsigned char. Depending on the implementation used, a char might be signed or unsigned.
| Type | Explanation | Min Macro | At least Min Value | Max Macro | At least Max Value |
|---|---|---|---|---|---|
| char | Either a "signed char" or a "unsigned char". | CHAR_MIN | CHAR_MAX | ||
| signed char | Same as char, guaranteed to be signed. | SCHAR_MIN | -127 | SCHAR_MAX | +127 |
| unsigned char | Same as char, guaranteed to be unsigned. | 0 | UCHAR_MAX | +255 | |
Signed Integer Types
The standard defines five signed integer types:
- signed char
- short int
- int
- long int
- long long intC99
In this list, each type provides at least as much storage as those preceding it.
| Type | Explanation | Min Macro | At least Min Value | Max Macro | At least Max Value | since |
|---|---|---|---|---|---|---|
| short short int signed short signed short int |
Short signed integer type. At least 16 bits in size. |
SHRT_MIN | -32767 | SHRT_MAX | +32767 | C89 |
| int signed int |
An integer type. At least 16 bits in size. |
INT_MIN | -32767 | INT_MAX | +32767 | |
| long long int signed long signed long int |
A long integer type. At least 32 bits in size. |
LONG_MIN | -2147483647 | LONG_MAX | +2147483647 | |
| long long long long int signed long long signed long long int |
A long long integer type. At least 64 bits in size. |
LLONG_MIN | -9223372036854775807 | LLONG_MAX | +9223372036854775807 | C99 |
The macros in the table can be found in the <limits.h> header.
