Basic types
The C language provides the four basic arithmetic type specifiers char, int, float and double, and the modifiers signed, unsigned, shortand long. The following table lists the permissible combinations to specify a large set of storage size-specific declarations.
| Type | Explanation | Format Specifier |
|---|---|---|
| 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. It contains CHAR_BIT bits.[3] |
%c |
| signed char | Of the same size as char, but guaranteed to be signed. Capable of containing at leastthe [−127, +127] range;[3][4] |
%c (or %hhi for numerical output) |
| unsigned char | Of the same size as char, but guaranteed to be unsigned. Contains at least the [0, 255] range.[5] |
%c (or %hhu for numerical output) |
| short short int signed short signed short int |
Short signed integer type. Capable of containing at least the [−32,767, +32,767] range;[3][4] thus, it is at least 16 bits in size. The negative value is −32767 (not −32768) due to the one's-complement and sign-magnitude representations allowed by the standard, though the two's-complement representation is much more common.[6] | %hi |
| unsigned short unsigned short int |
Short unsigned integer type. Contains at least the [0, 65535] range;[3][4] | %hu |
| int signed signed int |
Basic signed integer type. Capable of containing at least the [−32,767, +32,767] range;[3][4] thus, it is at least 16 bits in size. | %i or %d |
| unsigned unsigned int |
Basic unsigned integer type. Contains at least the [0, 65535] range;[3][4] | %u |
| long long int signed long signed long int |
Long signed integer type. Capable of containing at least the [−2,147,483,647, +2,147,483,647] range;[3][4] thus, it is at least 32 bits in size. | %li |
| unsigned long unsigned long int |
Long unsigned integer type. Capable of containing at least the [0, 4,294,967,295] range;[3][4] | %lu |
| long long long long int signed long long signed long long int |
Long long signed integer type. Capable of containing at least the [−9,223,372,036,854,775,807, +9,223,372,036,854,775,807] range;[3][4] thus, it is at least 64 bits in size. Specified since the C99 version of the standard. | %lli |
| unsigned long long unsigned long long int |
Long long unsigned integer type. Contains at least the [0, +18,446,744,073,709,551,615] range;[3][4] Specified since the C99 version of the standard. | %llu |
| float | Real floating-point type, usually referred to as a single-precision floating-point type. Actual properties unspecified (except minimum limits), however on most systems this is the IEEE 754 single-precision binary floating-point format. This format is required by the optional Annex F "IEC 60559 floating-point arithmetic". | for formatted input: %f %F for digital notation, or %g %G, or %e %E %a %A for scientific notation[7] |
| double | Real floating-point type, usually referred to as a double-precision floating-point type. Actual properties unspecified (except minimum limits), however on most systems this is the IEEE 754 double-precision binary floating-point format. This format is required by the optional Annex F "IEC 60559 floating-point arithmetic". | %lf %lF %lg %lG %le %lE %la %lA;[7]for formatted output, the length modifier l is optional. |
| long double | Real floating-point type, usually mapped to an extended precision floating-point number format. 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 the article on long double for details. | %Lf %LF %Lg %LG %Le %LE %La %LA[7] |
Boolean type
C99 added a boolean (true/false) type _Bool. Additionally, the new <stdbool.h> header defines bool as a convenient alias for this type, and also provides macros for true and false. _Bool functions similarly to a normal integral type, with one exception: any assignments to a _Bool that are not 0 (false) are stored as 1 (true). This behavior exists to avoid integer overflows in implicit narrowing conversions. For example, in the following code:
unsigned char b = 256;
if (b) {
/* do something */
}
b evaluates to false if unsigned char is 8 bits wide. This is because 256 does not fit in the data type, which results in the lower 8 bits of it being used, resulting in a zero value. However, changing the type causes the previous code to behave normally:
_Bool b = 256;
if (b) {
/* do something */
}
