Basic Types
The C language provides many basic types. Most of them are formed from one of the four basic arithmetic type identifiers in C (char, int, float and double), and optional specifiers (signed, unsigned, short, long). All available basic arithmetic types are listed below:
| Type | Explanation | Type | Explanation |
|---|---|---|---|
| char | smallest addressable unit of the machine that can contain basic character set. It is an integer type. Actual type can be either signed or unsigned depending on implementation | signed char | same as char, but guaranteed to be signed. |
| unsigned char | same as char, but guaranteed to be unsigned. |
||
| short short int signed short signed short int |
short signed integer type. At least 16 bits in size. | unsigned short unsigned short int |
same as short, but unsigned. |
| int signed int |
basic signed integer type. At least 16 bits in size. | unsigned unsigned int |
same as int, but unsigned. |
| long long int signed long signed long int |
long signed integer type. At least 32 bits in size. | unsigned long unsigned long int |
same as long, but unsigned. |
| long long long long int signed long long signed long long int |
long long signed integer type. At least 64 bits in size. Specified since the C99 version of the standard. | unsigned long long unsigned long long int |
same as long long, but unsigned. Specified only in C99 version of the standard. |
| float | (single precision) floating-point type. Actual properties unspecified, however on most systems this is IEEE 754 single precision floating point format. | ||
| double | double precision floating-point type. Actual properties unspecified, however on most systems this is IEEE 754 double precision floating point format. | ||
| long double | extended precision floating-point type. Actual properties unspecified. Unlike types float and double, it can be either 80-bit floating point format, the non-IEEE "double-double" or IEEE 754 quadruple precision floating-point format if a higher precision format is provided, otherwise it is the same as double. See this page for details. |
The actual size of integer types varies by implementation. The only guarantee is that the long long is not smaller than long, which is not smaller than int, which is not smaller than short. Also, int should be the integer type that the target processor is most efficient working with. This allows great flexibility: for example, all types can be 64-bit. However, only several different integer width schemes (data models) are popular and since data model defines how different programs communicate, a uniform data model is used within a given operating system application interface.
The actual size of floating point types also varies by implementation. The only guarantee is that the long double is not smaller than double, which is not smaller than float. Usually, 32-bit and 64-bit IEEE 754 floating point formats are used, if supported by hardware.
Read more about this topic: C Data Types
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