D constrains integral types to specific sizes. But efficiency of different sizes varies from machine to machine, pointer sizes vary, and the maximum integer size varies.stdint offers a portable way of trading off size vs efficiency, in a manner compatible with thestdint.h definitions in C.

In the table below, theexact aliases are types of exactly the specified number of bits. Theat least aliases are at least the specified number of bits large, and can be larger. Thefast aliases are the fastest integral type supported by the processor that is at least as wide as the specified number of bits. The aliases are:

Exact Alias	Description	At Least Alias	Description	Fast Alias	Description
int8_t	exactly 8 bits signed	int_least8_t	at least 8 bits signed	int_fast8_t	fast 8 bits signed
uint8_t	exactly 8 bits unsigned	uint_least8_t	at least 8 bits unsigned	uint_fast8_t	fast 8 bits unsigned
int16_t	exactly 16 bits signed	int_least16_t	at least 16 bits signed	int_fast16_t	fast 16 bits signed
uint16_t	exactly 16 bits unsigned	uint_least16_t	at least 16 bits unsigned	uint_fast16_t	fast 16 bits unsigned
int32_t	exactly 32 bits signed	int_least32_t	at least 32 bits signed	int_fast32_t	fast 32 bits signed
uint32_t	exactly 32 bits unsigned	uint_least32_t	at least 32 bits unsigned	uint_fast32_t	fast 32 bits unsigned
int64_t	exactly 64 bits signed	int_least64_t	at least 64 bits signed	int_fast64_t	fast 64 bits signed
uint64_t	exactly 64 bits unsigned	uint_least64_t	at least 64 bits unsigned	uint_fast64_t	fast 64 bits unsigned

The ptr aliases are integral types guaranteed to be large enough to hold a pointer without losing bits:

Alias	Description
intptr_t	signed integral type large enough to hold a pointer
uintptr_t	unsigned integral type large enough to hold a pointer

The max aliases are the largest integral types:

Alias	Description
intmax_t	the largest signed integral type
uintmax_t	the largest unsigned integral type

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