FRONT END

by Peter Zoeteweij

from Your Sinclair, June 1989



I was about to put out a nationwide APB for this sort of program in

the hope of a response when suddenly a parcel eased through my letter-

box. And inside? A you-guessed-it written by none other than Peter

"ah,ah,ah" Zoeteweij (bless you).



The Program

The program is designed to be welded onto the front of a Basic or

machine code game (hence the name) to provide the option of joystick

or keyboard play. It's easy to use, simple to type in, and straight-

forward to understand. Peter's even supplied a 'game' (the term 'game'

here is used in the broadest sense of the word - you'll see why if you

type it in) to show you how it can be used.



Method

Using the hex loader program, enter the 443 bytes of machine code, and

then SAVE "control" CODE 65000,443. Then type in the 'game' and

examine the listing for further information.



Techno-Bilge

The routine doesn't actually print a menu up for you. That part is

entirely handled by a program in Basic. Each option (Keyboard,

Kempston, Sinclair, Cursor) has a corresponding routine in machine

code. The addresses run as follows:

KEYBOARD (define keys) 65000

Select KEMPTSON        65003

Select SINCLAIR        65006

Select CURSOR          65009

Calling each of the individual routines programs the main Keyscan

routine at 65012. So, for example, if you RANDOMIZE USR 65006 the

keyscan routine will change to accept Sinclair joystick only.



Once this has been done you call the scan routine in order to accept

inputs. Any inputs are coded and placed at memory address 65535. So to

find out which direction has been selected:

LET a=PEEK 65535

a=10    a=8     a=9

a=2             a=1

a=6     a=4     a=5