inttypes.h
 | It has been suggested that this article be merged into C data types. (Discuss) Proposed since October 2011. |
| C standard library (libc) |
|---|
| General topics |
| Miscellaneous headers |
The inttypes.h file is a C header file that is part of the C standard library and API. It was added with the 1999 version of the ISO C standard (known as C99). It includes the stdint.h header and defines a number of macros for using it with the printf and scanf family of functions, as well as functions for working with the intmax_t type.
Naming Convention for Macros
The macros defined in inttypes.h follow a regular pattern to simplify usage. The pattern followed is as follows [1] :
First three characters
Fourth character
- d for decimal formatting
- x for hexadecimal formatting
- o for octal formatting
- u for unsigned int formatting
- i for integer formatting
Remaining Characters
- N for N bit size assignment to the data type (Eg. 32 for 32-bit size for int), 16 for 16-bit size for unsigned and so on)
- PTR for pointer
- MAX for maximum supported bit size
- FAST, whose meaning is not clearly defined and is left to the implementation to decide what is meant by a "fast" integer data type.
The following table gives syntax used for various data types listed in inttypes.h:
| Fixed width integer | signed | unsigned |
|---|---|---|
| 8 bit | int8_t | uint8_t |
| 16 bit | int16_t | uint16_t |
| 32 bit | int32_t | uint32_t |
| 64 bit | int64_t | uint64_t |
| Small & fixed integer types | signed | unsigned |
|---|---|---|
| 8 bit | int_least8_t | uint_least8_t |
| 16 bit | int_least16_t | uint_least16_t |
| 32 bit | int_least32_t | uint_least32_t |
| 64 bit | int_least64_t | uint_least64_t |
| Fast & fixed integer types | signed | unsigned |
|---|---|---|
| 8 bit | int_fast8_t | uint_fast8_t |
| 16 bit | int_fast16_t | uint_fast16_t |
| 32 bit | int_fast32_t | uint_fast32_t |
| 64 bit | int_fast64_t | uint_fast64_t |
Dependency Graph
Dependency graph for inttypes.h[2]
Rationale
|
The difference in processing speeds in different processors like 16-bit, 32-bit and 64-bit systems, called for a uniform size for various data types. ISO/IEC 9899:1990 specified that the language should support basic data types like char, int, short and long but did not restrict the minimum or maximum size for these data types, expect that int be at least 16-bits long and long be 32-bits long.
In 16-bit systems, most implementations assigned 8, 16, 16 and 32 bits for char, int, short and long data types, respectively. In 32-bit systems, it was 8, 32, 16 and 32 bits for char, int, short and long data types[1]. The difference in size of int caused problems to users who migrated from one system to another.
The main purpose of including this header file is to restrict, or in other words, limit the exact size of int data type to a particular value(may be 16 bits or 32 bits)[3]. It can also be used to limit the size of data type modifiers like unsigned int and signed to specific values by using the macros listed in the header file.[4]
See also
References
- ^ a b http://manpages.ubuntu.com/manpages/gutsy/man7/inttypes.h.7posix.html
- ^ http://api.plexyplanet.org/inttypes_8h.html
- ^ The Open Group Specifications Issue 6. "Application Usage and Rationale". The IEEE and The Open Group.
{{cite web}}: CS1 maint: numeric names: authors list (link) - ^ The Open Group Specifications Issue 6. "Application Usage and Rationale". The IEEE and The Open Group Base. Retrieved 14 September, 2011.
{{cite web}}: Check date values in:|accessdate=(help)CS1 maint: numeric names: authors list (link)
External links
- : fixed size integer types – Base Definitions Reference, The Single UNIX Specification, Version 5 from The Open Group
- inttypes.h header file for Visual C++ (requires a compatible stdint.h).
- C++ reference for fixed width integer types inherited from C
- Macro definitions and their interpretation in inttypes.h
- Writing machine-independent code
- Apple's open source code for inttypes.h