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There are even calculators that perform number base conversions. Often this conversion has to be performed in a program, for instance when a number is entered by the user and then processed by the computer. In this case the number entered, being simply a combination of graphic symbols, is evaluated and then usually converted into a binary number, in effect, a word or a long word. This process is often required in reverse order, as well. If the computer is to display a calculated value in a specific number system, it must first convert that number into a series of characters.

In a later chapter you will develop machine language routines to solve these problems. You can then use these routines in your own programs. First you still have to cover some things that are fundamental to machine language programming on the Amiga. Introduction 1. These are referred to as the "custom" chips, which perform various tasks independently of the processor.

Custom chips This task force is comprised of three chips, whose poetic names are Agnus, Denise and Paula. The main task of Agnus, alias blitter, is the shifting of memory blocks, which is helpful for operations such as quick screen changes.

To simplify the otherwise rather complicated procedure of utilizing these chips, several programs have been included in the Kickstart and Workbench libraries. These programs can be called by simple routines and then take over the operation of the respective chips.

If only these library functions are used to program the Amiga, the parameters are the same, regardless of the language used. Only the parameter notation differs from language to language. The library functions are written in machine language and are thus closely related with your own machine language programs. Actually you could do without the library programs and write all of the functions yourself. With the release of AmigaDOS 1. This allows you to add memory and without worrying about addresses and dip switches.

Thus, graphics and sound data handled by these chips must be stored in this memory range. Because of this, that memory range is referred to as chip RAM.

Since only the processor itself has access to this part of memory it is known as fast RAM. The memory range thus occupied is added to a list of occupied memory and the memory range is then considered barred from other uses. If another program is loaded, which is quite possible with the Amiga, it is read into another memory 10 Abacus 1. Introduction location which is then marked on the occupied list. If the first program should require additional memory, to use a text buffer for example, that memory first has to be reserved.

Otherwise another program could accidentally be loaded into the memory needed for this task. As a result, RAM is then chopped up into occupied and free parts, which are no longer related to each other. The Amiga can still utilize these chunks of memory as if they were one continuous chunk. After all, parts is parts. This RAM disk is actually quite a phenomenon, since it is always completely filled. If a program is erased from RAM disk, the memory allocated to that program, regardless of its location and structure, is given back to the system.

Thus, if you reserve and fill Kbytes of memory, it would be quite possible that the Kbytes actually consist of various pieces of memory independent of one another. You never notice this since the Amiga automatically corrects the difference between apparent and actual memory. However, there is a catch to this: even the Amiga has only one processor, which can really only do one thing at a time. The tricky part is when more than one program is running, each program is executed part by part, and the Amiga is constantly switching from one program back to the other program.

This procedure would be repeated over and over, as the three programs are executed together. The problem is, that the greater the workload on the processor, the slower things happen. Thus, programs run slower during heavy multi-tasking.

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Amiga machine language



Amiga Machine Language 68000 Assembler ©1988 Abacus Book #4 for Commodore Amiga



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