What is the difference between byte addressing and word addressing?

Difference: 1. Byte addressing means that each different state of a group of address lines corresponds to a byte address, while word addressing means that each different state of a group of address lines corresponds to The address of a word; 2. The number of addressing bits for byte addressing is 8 bits, while the number of addressing bits for word addressing is 32 bits or 64 bits; 3. The addressing range is different, for a capacity of 16MB For memory, the range of byte addressing is 16M, while the addressing range of word addressing is related to the word length. If it is addressed by a 16-bit long storage word, the range is 8M. If it is addressed by a 32-bit word length, Addressing, the range is 4M.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What are word addressing and byte addressing?

If you want to do it, please use word addressing and byte addressing. We must first clarify the definitions of bits, bytes, word lengths, and words:

• Bit: the smallest unit of data storage. The smallest data unit in the computer, the value of a bit can only be 0 or 1

• byte: It is composed of eight-digit binary numbers and is the most basic unit of measurement in the computer. The most important unit of measurement (personal understanding).

• Word length: The number of digits in the maximum binary number that the CPU can process in unit time in the computer is called the word length.

• Word: A word is a unit in different computer systems that occupies a separate address (the number of a memory unit) and is processed as a unit (composed of one or more bytes). Group of binary numbers.

The following is the understanding of word addressing and byte addressing:

• Byte addressing: the most popular understanding It is a set of address lines where each different state corresponds to a byte address. For example, if there are 24 address lines, which are addressed by byte, and each line has two states, then the address signal composed of 24 address lines has 224 different states, and each state corresponds to a byte address space. , the addressable space of 24 address lines is 224B, which is 16MB.

• Word addressing: The most popular understanding is that each different state of a set of address lines corresponds to the address of a word. Because the byte is the most basic unit of measurement in the computer and a word is composed of several bytes, the computer will distinguish the bytes in the word during the addressing process, that is, it will address the bytes in the word, which will occupy Part of the address line. For example, there are 24 address lines, and the word length is 16 bits. 16 bits is two bytes. This will occupy one address line for intra-word addressing, leaving 23 address lines. So the addressing range is 223W, which is 8MW, where W means the word length.

Word addressing VS byte addressing

The number of addressing bits is different

• Byte addressing: The number of bits used in addressing is 8 bits.

• Word addressing: Word refers to the storage word length, not two bytes, which is often referred to as 32-bit or 64-bit.

Different addressing ranges

For a certain capacity of memory, the addressing ranges for word access and byte access are different. of.

For example: a memory with a capacity of 16MB, the range of byte addressing is 16M, that is to say, 2 to the 24th power, corresponding to 24 address lines; if it is addressed by words, then the addressing The range is related to the word length. For a 16MB memory, if it is addressed by a 16-bit long storage word, the addressing range is 8M. If it is addressed by a 32-bit word length, the addressing range is 4M.

The following is explained with pictures:

#The same is true for the 32-bit word length. The high 22 bits of the 24 address lines correspond to the 4M addressing range, and the last two bits Corresponding to the address of 4 bytes in 32 bits

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