SINCLAIR USER, November 1984
Starter Pack


= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 


Password (Spectrum)
by Hamish Barr
[not done yet]


= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 


Driver (1K ZX-81)
by D. Gough

DRIVER by D Gough of Ashton-under-Lyme in Manchester is probably the simplest 
playable game possible on the unexpanded ZX-81. You must use cursor keys 5 
and 8 to control the car, avoiding the obstacles in your way.

Variables used:
A:           Holds the horizontal position of the car. 
S:           Keeps the score.

Line 10      Sets the horizontal position of the car to 11, which is about a 
             third of the way across the screen.
Line 20      Sets the score to zero.
Line 30      Prints one obstacle at line 21, the bottom of the screen, and at 
             a random position along that line. The obstacle is represented 
             by three asterisks.
Line 40      Sets the print position at the same place as the position of the 
             car. Before the car is printed to the screen, we must check to 
             see that there is nothing already there. That will not happen 
             the first time, but may happen later in the game.
Line 50      This line is one of the most useful programming devices for 
             the ZX-81. It looks directly at the bytes 16398 and 16399 in 
             the systems variable area of the memory, which you would not 
             usually use. Those stores contain the address of the square on 
             the screen where the computer is to print the next character. 
             It then looks at that byte to see whether there is already 
             something there, in this case code number 23, which is the 
             code number of the asterisk. You can find the code numbers 
             for characters in Appendix A of your ZX-81 manual. So, taken 
             together, lines 50 and 60 set the print position to where the 
             car should be printed next, and then check to see if there is an 
             asterisk already on the screen in that position.
               If there is an asterisk there, then you have crashed, and the 
             program jumps to line 120.
Line 60      Prints the car at the pre-arranged print position, which we 
             now know to be clear of obstacles.
Line 70      Moves the whole display up one line, bringing the new 
             obstacles closer to the car, and leaving room at the bottom for 
             a new one. Any obstacles going off the top of the screen will be lost.
Lines 80-90  Check the keyboard to see which keys you are pressing. If you 
             are pressing 5 or 8 then the position of the car must
             change, and A is adjusted accordingly.
Lrnc 100     Adds ten to your score.
Line 110     Sends you back to the beginning of the main part of the program.
Line 120     You have crashed, so the computer prints out your score and 
             then stops.

You could easily adapt the program, still in 1K, to make the game get 
harder as you play. One possible method would be to have a new variable, 
say A$, containing the obstacle, and change that each time the score 
reached a particular level.


= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 


Black Swan

Extremely effective use of the user-defined graphics on the 16K
Spectrum make this game by Michelle Presslie, of Dudley in the West
Midlands, a pleasure to watch. You are a swallow who must eat as many
gnats as possible in as short a time as you can, while below a black
swan swims elegantly among the bulrushes.


= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 


