Built-in Assembler Register Symbols


 Built-in Assembler Register Symbols

In Turbo Pascal's built-in assembler, the following reserved symbols denote CPU registers:

   Symbols              Registers

   AX BX CX DX          16-bit general purpose
   AL BL CL DL          8-bit low registers
   AH BH CH DH          8-bit high registers
   SP BP SI DI          16-bit pointer or index
   CS DS SS ES          16-bit segment registers
   ST                   8087 register stack

When an operand consists solely of a register name, it is called a register operand. All registers can be used as register operands.

Register Indexing

The base registers (BX and BP) and the index registers (SI and DI) can be written within square brackets to indicate indexing.

These are valid index register combinations:


Segment Overriding

The segment registers (ES, CS, SS, and DS) can be used in conjunction with

 the colon (:) segment override operator to indicate a different segment than

the one the processor selects by default.

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