Machine Word length storage word length instruction word length data word length

Machine Word Length: The number of bits that the CPU can process data at a time, usually related to the number of registers of the CPU.
Storage Word Length: The number of bits of binary code stored by a storage unit (storage address) in memory, that is, the number of MDR in memory.
Instruction word Length: The number of bits of the computer instruction character.
Data word Length: The number of bits occupied by the computer data store.

Note: von Neumann machine, instruction and data are equally important, are stored in the memory, and can be searched by address.

usually early computers: Store word length = instruction word length = data word length. Therefore, it is advisable to visit a command or a data, as the scope of computer applications are constantly expanding, the three may be different, but they must be an integer multiple of bytes.

Information storage units in a computer

The information in the computer is represented by binary, and the commonly used units are bits, bytes, and words.

1, bit (bit): is the smallest unit of data in a computer, storing a binary number, that is, 0 or 1. It is also the smallest unit of memory storage information, usually denoted by "B".

2, Byte (Byte): bytes are the most common basic unit in a computer that represents storage capacity. A byte consists of a 8-bit binary number, usually denoted by "B". One character occupies one byte, and one Chinese character occupies two bytes. Other common storage units are:

Storage capacity is measured in bytes B, Kbytes, megabytes, and 1 billion gigabytes (GB). The conversion relationship between them is as follows:

1KB (kilobyte KB) =1024b
1MB (megabyte megabyte abbreviation "mega") =1024kb
1GB (Gigabyte gigabyte, also known as "gigabit") =1024MB
1TB (Trillionbyte trillion bytes MBytes) =1024gb
1PB (petabyte petabyte Word ticks byte) =1024TB
1EB (Exabyte exascale byte ai byte) =1024pb
1ZB (zettabyte 10 trillion byte ze byte) = 1024x768 EB
1YB (jottabyte 100 million bytes yao byte) = 1024x768 ZB
1BB (brontobyte 100 billion bytes) = YB

3, Word and word length: The word refers to a set of binary numbers that are accessed, transmitted, and processed as a whole in a computer. The number of bits (that is, the word length) is an important feature in the structure of a computer system. Word length is determined by the type of CPU, different computer systems, the word length is different, the common 8-bit, 16-bit, 32-bit, 64-bit, the longer the word length, the more information the computer processing, the higher the accuracy, the word length is an important indicator of computer performance, At present, the mainstream microcomputer is changing from 32-bit machine to 64-bit machine.

Note the difference between words and word lengths, words are units, and word length is the indicator.

The length of the machine affects the speed of the machine's operation. If the CPU length is short, but also the number of operations more data, then need to go through two or more operations to complete, which will inevitably affect the speed of the whole machine.

The length of the machine has a great impact on the cost of the hardware. It will directly affect the adder (or ALU), the data bus, and the number of bits that store the word length. So the machine word length can not be considered simply from the precision and the range of representation.

In order to adapt to the different requirements and the relationship between the computational precision and the hardware cost, most computers support variable word length operations, that is, half-length, full-length (or single-word length) and double-length operations can be realized in the machine.

Machine Word length storage word length instruction word length data word length