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The reason for this is that a byte is normally the smallest unit of addressable memory (i.e. data with a unique memory address). This applies to bitwise operators as well, which means that even though they operate on only one bit at a time they cannot accept anything smaller than a byte as their input.
The basic unit of digital storage is a bit, storing a single 0 or 1. Many common instruction set architectures can address more than 8 bits of data at a time. For example, 32-bit x86 processors have 32-bit general-purpose registers and can handle 32-bit (4-byte) data in single instructions. However, data in memory may be of various lengths.
Content-addressable memory (CAM) is a special type of computer memory used in certain very-high-speed searching applications. It is also known as associative memory or associative storage and compares input search data against a table of stored data, and returns the address of matching data. [1]
Memory and other devices would be added to the bus using the same address and data pins as the CPU itself used, connected in parallel. Communication was controlled by the CPU, which read and wrote data from the devices as if they are blocks of memory, using the same instructions, all timed by a central clock controlling the speed of the CPU.
Most modern computers are byte-addressable. Each address identifies a single byte of storage. Data larger than a single byte may be stored in a sequence of consecutive addresses. There exist word-addressable computers, where the minimal addressable storage unit is exactly the processor's word.
The EEPROM is memory-mapped in some devices; in others, it is not directly addressable and is instead accessed through address, data and control I/O registers. The general purpose registers, the status register and some I/O registers are bit-addressable, with bit 0 being the least significant and bit 7 the most significant.
A memory address a is said to be n-byte aligned when a is a multiple of n (where n is a power of 2). In this context, a byte is the smallest unit of memory access, i.e. each memory address specifies a different byte. An n-byte aligned address would have a minimum of log 2 (n) least-significant zeros when expressed in binary.
The DEC PDP-10, also 36-bit, had special instructions which allowed memory to be treated as a sequence of fixed-size bit fields or bytes of any size from 1 bit to 36 bits. A one-word sequence descriptor in memory, called a "byte pointer", held the current word address within the sequence, a bit position within a word, and the size of each byte.