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Written By John Wilson


Cover Art
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Loading Screen
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Opening Screen
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Game Screenshot

Centipede

JR Wilson with an arcade game for the BBC

Centipede is a games program for the BBC Model B or Model A with 32K RAM. The program makes extensive use of machine code and the BBC's graphics to make a high speed arcade type game.

You control Fred, from the local pest control department, and are faced with a terrible task. Armed only with your trusty spray gun, you must face a garden full of mutated mushrooms and bugs.

There are 15 different options available from an option page, which can be accessed at any time by pressing the Escape key.

Game Controls

The initial control keys are as follows:

Z - Left, X - Right, : - Up, / - Down, RETURN - Fire spray gun

The program includes a pause facility to stop the game at any stage for more pressing interruptions.

One final note. Fred earns another charge for his antidote when your score reaches 5,000 points.

The Program Listings

The first program to be typed out is the large assembly language program, and is shown in listing four. It will take a lot of time and effort to get through this program without making mistakes, so take your time. Before you attempt this, I suggest that you reset PAGE to &1B00 by typing:

PAGE=&1B00 (RETURN)
NEW (RETURN)

You will then have to reset PAGE to &1B00 after pressing the Escape key. The program as listed will assemble machine code from &D00 upwards, so for disc users, the Break key must be pressed and PAGE reset before the program can be saved. Once you have finished typing it in, save the program on a separate cassette for a backup copy. Then RUN the program, but press the Escape key when asked whether to save the machine code.

It is now time to type out listing 1.

Once this program is working correctly it should be saved onto a separate cassette, at the beginning, by:

SAVE "CENTI"

The second program shown in listing 2 can now be typed out, and can be saved after "CENTI" by:

SAVE "CENTI1"

Once the program has been typed out, it should be saved after "CENTI1" by

SAVE "CENTI2"

The third program will only work if the machine code is also in memory. Therefore, it is now time to save the machine code following this program on tape. So, load in the assembler program again and RUN it. Allow the program to record the machine code by pressing the Break key when told.

The game was written on a BBC fitted with the 1.2 Operating System, but should work on any non-0.1 OS. The programs are also suitable for use with disc or tape systems without modifications.