Commodore 16

Introduction

The Commodore 16 is a microcomputer that came out in 1984 and was supposed to build on the success of the VIC-20 (please see Commodore VIC-20) but ended up selling badly. At the hardware level it is very similar to the Commodore Plus 4 (see Commodore/Plus 4), having the same 8501 CPU (which was based on the 6502) and video chip "TED" (Text Editing Device), but with a lower amount of RAM, no additional built-in software and no user port.

Introduction

Overview

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Overview

Unfortunately, as with the Commodore Plus 4, the Commodore 16 had quite a high failure rate. Most commonly, either the CPU stopped working or the TED chip or sometimes the keyboard. As the TED did much more than just display graphics (it created sound, refreshed the RAM, handled the keyboard and more) and ran at a much higher clock speed than the CPU, in some ways it's not surprising that the TED tended to die through overheating.

A strength of the Commodore 16 was its more advanced built-in BASIC which supported drawing (for its time) high resolution graphics, unlike the VIC-20 (high resolution graphics was only possible on the VIC-20 by manipulating the text characters). Another feature of the BASIC was its provision for entering BASIC keywords quicker by typing the first letter followed by shift and the second letter pressed at the same time.

Another plus point of the Commodore 16 was its built-in machine code monitor which could be used to create, test and debug machine code programs. There are a number of ways to enter the machine code monitor:

* When in BASIC type MONITOR and return or M shift-O and return. Type X and return to exit to BASIC.

* Hold Run/Stop and power on. Note: sometimes typing X and return doesn't exit to BASIC.

* Hold Run/Stop and press reset.

It is possible to write a program in BASIC and then view it in raw form using the machine code monitor and even change the BASIC program. It is a good way to learn how BASIC programs are stored in memory.

Another trick is to load a program from tape, for example, and while the program is running you can enter the machine code monitor by holding Run/Stop and pressing reset. Then you will be able to view the loaded program (if you know where it's stored), edit it and learn how it works.

The Run/Stop and reset method of accessing the machine code monitor is helpful for debugging machine code programs as it usually keeps your program in memory even after a crash.