CODEWITHSUNDEEP
assemblyx86nasm
user4407915
user4407915

Reputation:

Why a Word is 2 bytes and not 4 bytes in x86 Assembly?

if a Word is the natural unit of data used by a particular processor, so in a x86 processor it is 4 bytes, then why in NASM and other assemblers the DW (Define Word) allocates 2 bytes of memory and not 4 bytes?

Upvotes: 3

Views: 2070

Answers (2)

Thorsten Staerk
Thorsten Staerk

Reputation: 1156

For historical reasons. The x86 family started as a 16-bit architecture (8086). That was the time when the instruction set was defined, and all further processors have to be backward-compatible.

The 80386 was the first 32-bit processor in the x86 series.

BTW I am writing an assembler tutorial and I think I'll put your question as an example there. Thanks!

Upvotes: 4

Christian Hujer
Christian Hujer

Reputation: 17945

That is due to historic reasons. The first member of the x86 processor family was the 8086, and in the 8086 was mostly a 16 bit processor.

As a historical side note, originally byte meant word, because at first, computers had only one width of data they could process, and byte was that width, and that width was also called character (that's why a byte is called char in C). Then computers grew, and things have become defacto standards...

Upvotes: 1

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