Dr Beep quiz

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
dr beep
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Re: Dr Beep quiz

Post by dr beep »

WHICH SYSTEM DID YOU NOT EMULATE ON THE ZX SPECTRUM?
A GAMEBOY

The idea is still to emulate this on a SAM Coupe
dr beep
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Re: Dr Beep quiz

Post by dr beep »

HOW MANY BYTES HAS THE SMALLEST SCREEN ON A ZX81?
1


You can make an empty screen with just 1 byte: #E9 = JP (HL)

You can use the same byte also to shorten a screen.
Display a few lines and then end the screen with JP (HL).

It is a trick I use often in my games.
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Re: Dr Beep quiz

Post by dr beep »

HOW MANY BYTES CAN YOU LOAD IN
1K FROM TAPE WITHOUT PROBLEMS?

949

Sometimes 950 or 951 is possible but the game could also crash.

You load at #4009 so another 9 bytes are never loaded.

The rest of the 1K RAM is needed for intrupts and stack.
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Re: Dr Beep quiz

Post by dr beep »

WHICH GAMES PLANNED FOR THE ZX SPECTRUM ENDED ON A ZX81?

MINITAURUS AND CALCULUS MAZXIMUS

As long as I had a ZX Spectrum I wanted to make a version of these games on the ZX Spectrum.
Of both I started some code but both were never finished.
In the end the ZX81 was capable of doing what I wanted and even in 1K.


SOKOB1 is a port of a ZX Spectrumgame and YAHTK is also coded on the ZX Spectrum lathough the play is a bit different.

FINGERTWISTER and ZNAKE are 1K versions of earlier ONELINERS on the ZX Spectrum.
dr beep
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Re: Dr Beep quiz

Post by dr beep »

WHAT NUMBER IS THIS QUIZ IN YOUR LIST OF GAMES?
125

So far I have coded 125 games on the ZX81
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siggi
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Re: Dr Beep quiz

Post by siggi »

dr beep wrote: Mon Sep 09, 2024 8:21 pm You can make an empty screen with just 1 byte: #E9 = JP (HL)

You can use the same byte also to shorten a screen.
Display a few lines and then end the screen with JP (HL).
Does that also mean, that the program is running faster (no more NOPs need to be executed, less time is "wasted" for display)?
My ZX81 web-server: online since 2007, running since dec. 2020 using ZeddyNet hardware
http://zx81.ddns.net/ZxTeaM
dr beep
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Re: Dr Beep quiz

Post by dr beep »

siggi wrote: Sat Sep 14, 2024 11:23 am
dr beep wrote: Mon Sep 09, 2024 8:21 pm You can make an empty screen with just 1 byte: #E9 = JP (HL)

You can use the same byte also to shorten a screen.
Display a few lines and then end the screen with JP (HL).
Does that also mean, that the program is running faster (no more NOPs need to be executed, less time is "wasted" for display)?
Unfortunately not.
The screen will fill wit spaces and after 34 spaces the intrupt comes in and the next line is done untill all lines are displayed as spaces.

It is however possible to use some screentime for intruptroutines.
This is how CALCULUS MAZXIMUS checks the 20 seconds passed to alter the screen and go to inputmode.
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Re: Dr Beep quiz

Post by dr beep »

WHAT IS NOT A TRICK WITH HIDDEN OPCODES ON THE SCREEN?
YOU CAN PLACE AN INVERTED SPACE ON THE SCREEN

A hidden opcode will produce a normal space on the screen.



YOU CAN FIND A LOCATION ON THE SCREEN
This trick is used to display the escapeladders in LODERUNNER

YOU CAN STORE INFORMATION ON THE SCREEN WITHOUT SHOWING
This is the most used option, like the tail of a snake in ZNAKE or the direction of KILOPEDE
but also the number of bombs in MINESWEEPER.
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Re: Dr Beep quiz

Post by dr beep »

LD A,(DE)
LD L,A
LD H,B
LD H,(HL)
JP (HL)

THE OPCODESELECTIONROUTINE OF AN EMULATOR

This is the mainroutine in my emulators. SP-2-ZX81 has this code to emulate each possible opcode.
This routine is also used in the Galaksija-emulator from Andre Owen on the Sam-Coupe.

After years of trying this is the fastest mainroutine to go to the opcoderoutine belonging to the opcode.
dr beep
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Re: Dr Beep quiz

Post by dr beep »

NAME THE TYPE-IN GAME IN "THE ULTIMATE 1K CODING BOOK"?

BATTLESHIP

Easy one, isn't it?
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