BASIC programming tips

[Manuel3D]

thanks for your answer. I thought there might be a simple way that I didn't know about but I see that the solution is not easy. I have tried to put the image and call it from basic with a &call BB18 but as soon as I touch a letter on the keyboard the image disappears from the screen making its use impossible. I have seen on the internet that it can also be done using a library to program games from basic called 8BP. I have to find out more about the subject.

[BSC]

Let's see, if my memory still works well enough then this might do the trick if you have the image as a raw screen dump:

10 memory &3fff
20 load "[name of your image here]",&4000
30 for i=0 to 11:read k:poke &af00+i,k:next:end
40 data &21,0,&40,&11,0,&c0,1,&ff,&3f,&ed,&b0,&c9
50 call &af00

Then, after running the listing once, you can do GOTO 50 whenever you need to restore the image.

[Manuel3D]

Your idea works. Now I will have to adapt the program a little to reduce the memory used since it had already reached a good size but I think it can work  thanks to your help.

[McArti0]

BUT WHY ASM?     OUT &BC00,12:OUT &BD00,&10: POKE &b7c6,&40

Manuel3D. Have you read PM?

Maybe write this in a new topic.

You can use two screens to draw.
Visible when you set POKE b7c6,&C0
or invisible when you set POKE &b7c6,&40.
In this case you need to limit BASIC to 16kB by MEMORY &3FFF.
With these settings you can draw twice. Once you draw on the background in the visible part. Once on the invisible part where there is no background.
If you want to see the invisible screen, you do OUT &BC00,12:OUT &BD00,&10.
If you want to see the main screen again, you do OUT &BC00,12:OUT &BD00,&30

[Jean-Marie]

You can use the firmware for this:
CALL &BC06,&40
then
CALL &BC06,&C0

[Manuel3D]

Thank you McArti0 and Jean-Mary I will try this too.

[Manuel3D]

Thank you McArti0 and Jean-Mary I will try this too.

Sorry because I'm also new to this forum and I'm not used to how it works yet. Now for example, I wanted to quote you and it didn't work out. On the other hand, I see that this page works very slowly for me and often hangs and loads automatically.

[skylas]

Hi all!

If i remember well there was a command in BASIC for screen shaking.
Do I remember correct? I could not find it although I looked at the manual

[Sykobee (Briggsy)]

You want program 3 here - https://cpcrulez.fr/coding_src-list-graphic-crtc-on-screen_effects_on_the_CPC464_POPU.htm

[skylas]

You want program 3 here - https://cpcrulez.fr/coding_src-list-graphic-crtc-on-screen_effects_on_the_CPC464_POPU.htm

Many thx for your help!!! I thought it was only a command!

[BSC]

Your idea works. Now I will have to adapt the program a little to reduce the memory used since it had already reached a good size but I think it can work  thanks to your help.

If you are short on memory, you can change that little listing so that the screen is loaded to &6000 instead of &4000. I guess you can figure out what you have to change by yourself. Homework time!

[dodogildo]

Here's a PDF of an ages old book with Peeks and Pokes and other tips on Basic. Still holds tons of useful information.
(PEEKS et POKES du CPC - 1985)
https://shorturl.at/pCIM9