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The C language provides the four basic arithmetic type specifiers char, int, float and double (as well as the boolean type bool), and the modifiers signed, unsigned, short, and long. The following table lists the permissible combinations in specifying a large set of storage size-specific declarations.
Signed range (two's complement representation) Unsigned range 1 byte 8 bits Byte, octet, minimum size of char in C99( see limits.h CHAR_BIT) −128 to +127 0 to 255 2 bytes 16 bits x86 word, minimum size of short and int in C −32,768 to +32,767 0 to 65,535 4 bytes 32 bits
An integral type with n bits can encode 2 n numbers; for example an unsigned type typically represents the non-negative values 0 through 2 n − 1. Other encodings of integer values to bit patterns are sometimes used, for example binary-coded decimal or Gray code, or as printed character codes such as ASCII.
Programs that process years as 16-bit values may encounter problems dealing with either the year 32,768 or 65,536, depending on whether the value is treated as a signed or unsigned integer. For the year 32,768 problem, years after 32,767 may be interpreted as negative numbers, [5] [87] beginning with −32,768 which may be displayed as 32,768 BC.
The advantage over 8-bit or 16-bit integers is that the increased dynamic range allows for more detail to be preserved in highlights and shadows for images, and avoids gamma correction. The advantage over 32-bit single-precision floating point is that it requires half the storage and bandwidth (at the expense of precision and range). [5]
For example, a two's complement signed 16-bit integer can hold the values −32768 to 32767 inclusively, while an unsigned 16 bit integer can hold the values 0 to 65535. For this sign representation method, the leftmost bit ( most significant bit ) denotes whether the value is negative (0 for positive or zero, 1 for negative).
The largest consecutive integer in IEEE 754 single precision (2 24) 65,535: FFFF The maximum unsigned 16 bit value (2 16 − 1) 32,767 7FFF The maximum signed 16 bit value (2 15 − 1) 255: FF The maximum unsigned 8 bit value (2 8 − 1) 127 7F The maximum signed 8 bit value (2 7 − 1) −128 80 Minimum signed 8 bit value −32,768 8000
A common example is the Data General Nova, which was a 16-bit design that performed 16-bit math as a series of four 4-bit operations. 4-bits was the word size of a widely available single-chip ALU and thus allowed for inexpensive implementation. Using the definition being applied to the 68000, the Nova would be a 4-bit computer, or 4/16.