Search results
Results from the WOW.Com Content Network
Bit fields can be used to reduce memory consumption when a program requires a number of integer variables which always will have low values. For example, in many systems, storing an integer value requires two bytes (16-bits) of memory; sometimes the values to be stored actually need only one or two bits.
The C programming language's bit fields, pseudo-objects found in structs with size equal to some number of bits, are in fact small bit arrays; they are limited in that they cannot span words. Although they give a convenient syntax, the bits are still accessed using bytewise operators on most machines, and they can only be defined statically ...
For example, when shifting a 32 bit unsigned integer, a shift amount of 32 or higher would be undefined. Example: If the variable ch contains the bit pattern 11100101, then ch >> 1 will produce the result 01110010, and ch >> 2 will produce 00111001. Here blank spaces are generated simultaneously on the left when the bits are shifted to the right.
C also provides a special type of member known as a bit field, which is an integer with an explicitly specified number of bits. A bit field is declared as a structure (or union) member of type int, signed int, unsigned int, or _Bool, [note 4] following the member name by a colon (:) and the number of bits it should occupy. The total number of ...
In programming languages such as C, bit fields are a useful way to pass a set of named Boolean arguments to a function. For example, in the graphics API OpenGL , there is a command, glClear() which clears the screen or other buffers.
The alignment of particular fields in the struct (with respect to word boundaries) is implementation-specific and may include padding. Modern compilers typically support the #pragma pack directive, which sets the size in bytes for alignment. [1] The C struct feature was derived from the same-named concept in ALGOL 68. [2]
Bit field; Bit manipulation instruction set — bit manipulation extensions for the x86 instruction set. BIT predicate; Bit specification (disambiguation) Bit twiddler (disambiguation) Nibble — unit of data consisting of 4 bits, or half a byte; Predication (computer architecture) where bit "masks" are used in Vector processors; Single-event upset
Various rules in the C standard make unsigned char the basic type used for arrays suitable to store arbitrary non-bit-field objects: its lack of padding bits and trap representations, the definition of object representation, [7] and the possibility of aliasing. [12] The actual size and behavior of floating-point types also vary by implementation.