If you don't understand what the description of each part of memory means right now, this will become clear from other parts of this manual.
Machine language programs consist of instructions which may or may not have operands (parameters) associated with them. Each instruction takes up one memory location, and any operand is contained in one or two locations following the instruction.
In your BASIC programs, words like PRINT and GOTO do, in fact, only take up one memory location, rather than one for each character of the word. The contents of the location that represents a particular BASIC keyword is called a token. In machine language, there are different tokens for different instructions, which also take up just one byte (memory location=byte).
Machine language instructions are very simple. Therefore, each individual instruction cannot achieve a great deal. Machine language instructions either change the contents of a memory location, or change one of the internal registers (special storage locations) inside the microprocessor. The internal registers form the very basis of machine language.
This is THE most important register in the microprocessor. Various machine language instructions allow you to copy the contents of a memory location into the accumulator, copy the contents of the accumulator into a memory location, modify the contents of the accumulator or some other register directly, without affecting any memory. And the accumulator is the only register that has instructions for performing math.
This is a very important register. There are instructions for nearly all of the transformations you can make to the accumulator. But there are other instructions for things that only the X register can do. Various machine language instructions allow you to copy the contents of a memory location into the X register, copy the contents of the X register into a memory location, and modify the contents of the X, or some other register directly.
|This page has been created by Sami Rautiainen.|
|Read the small print.||Last updated December 08, 2002.|