"Assembly language" summary 02--[BX] and loop instructions

[BX] and [0] somewhat similar, [0] represents a memory unit, its offset address is 0, the same [BX] also represents a memory unit, its offset address in BX.

Loop, the English word "loop" has a circular meaning, obviously this instruction is related to the loop.

We agree that the symbol idata represents a constant, one thing to note here is that it is not possible to send a idata data directly into the segment register , which is illegal, and we can put the idata data into the Universal register first, The data in the General register is then mov to the segment register.

Debug and Assembler compiler MASM different processing of instructions:

1. Debug will interpret [Idata] as an offset address

2. MASM will interpret [idata] as an actual value idata

Segment prefix:

Instruction mov AX,[BX]

The offset address of the memory unit is given by BX, while the segment address is in DS by default, MOV ax,ds:[bx]

These appear in the instruction that accesses the memory unit, which is used to indicate "DS:", "CS:", "SS:", "es:" that indicate the segment address of the memory unit, and these are all referred to as segment prefixes.

A safe space:

In a normal PC, DOS and other legitimate programs do not generally use the 0:200~0:2FF 256-byte space, so we call this space safe.

Use of segment prefixes:

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Summary complete!

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"Assembly language" summary 02--[BX] and loop instructions