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Development - HELP WITH VPEEK,VPOKE..

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HELP WITH VPEEK,VPOKE..

NYYRIKKI
msx master
Berichten: 1503
Geplaatst: 10 Januari 2005, 21:03   
That was just a guess...

VPOKE is used to draw graphics to screen. VPEEK is used to read graphics from screen. These commands can't really be used for anything more interesting.

POKE is used to either write program to memory OR change some variables in memory, that can't be changed (or are not practical to change) other ways OR then POKE is just used to store bytes to memory in purpose to speed up arrays, when BASIC own arrays are too slow.

PEEK is typically used to read arrays or variables from memory as usually reading ML program from memory is not very interesting thing to do unless you are writing disassembler in BASIC.

In this case it might be that then the program either uses BIOS routines or the code is included in the BASIC program. Purpose to put bytes to memory is to write a ML code, that can be executed with DEFUSR & USR commands.

Here is an example of simple BASIC program:

10 beep:beep:beep

Here is an example of same program written using BEEP command from BIOS jump table:

10 DEFUSR=&HC0
20 A=USR(0)+USR(0)+USR(0)

Here is an example of home made ML program located at #C000, that executes BIOS BEEP command 3 times.

10 for i=0 to 8: read a: poke &HC000+i,a: next
20 defusr=&HC000: a=usr(0)
30 data 205,192,0,205,192,0,195,192,0

Hope this clears the idea a bit.

For more information:

Here is some more information about BIOS routines:
http://fms.komkon.org/MSX/Docs/BIOS.txt

Here is a list of ML op-codes, that you can POKE to memory to make your own programs:
http://www.z80.info/z80oplist.txt

I must anyway tell you, that most propably even those, who wrote your mentioned games, first made their routines in assembler, compiled them, tested them and then in last phase converted them to memory dump, that is written to memory by the BASIC program, you are able to see. This is propably done to make it possible to print the program to magazine.

From here you can also follow links to learn more about inner mind of Z80 CPU, that is the core of MSX:
http://www.z80.info/

Here is pretty good summary of MSX in general although quite some info is roughly generalized and violates MSX standard. This anyway should get you started:

http://www.work.de/nocash/portar.htm

To learn about usage of VPOKE and VPEEK, click first "Video Display Processor" and then "Video Modes"

To learn some basics about variables stored in RAM, look here:
http://fms.komkon.org/MSX/Docs/SysArea.txt

To learn, how to do things right and according to MSX standard I recommend you to read MSX2 technical handbook, that can be found from here:
http://www.konamiman.com/msx/msx-e.html

Msx-Basic
msx friend
Berichten: 10
Geplaatst: 11 Januari 2005, 09:24   
I am really so appreciated for your help all of you guys,and i do not know what to say
i searched other forums but i did not found like this forum,,
NYYRIKKI,do you mean that if i want to learn MSX2 ican use this technical book??
or no, i decided to learn MSX2 so what is the best e:book as you see and if there is put its link in this post,,if possible,,and if this technical book MSX2 was enough for learning i will read it and write a questions in this forum about what i did not understand.

thanks again
Msx-Basic

Msx-Basic
msx friend
Berichten: 10
Geplaatst: 11 Januari 2005, 09:28   
i forgot,,i do not have an MSX2 computer ,,I have MSX2 Emulator (Blue msx)
so it will be good for learn or not??
waiting for reply

[D-Tail]
online

msx guru
Berichten: 2994
Geplaatst: 11 Januari 2005, 11:20   
blueMSX is accurate enough to experiment your findings with. That is, if you've got a fast computer, like a Pentium III or a Pentium 4.
Sonic_aka_T

msx guru
Berichten: 2262
Geplaatst: 11 Januari 2005, 14:32   
msx-basic: blueMSX is fine indeed, it is quite accurate and you really shouldn't run into any trouble with it. The MSX2 computers are usually a little easier to learn on indeed, so they're a better choice. If you want to learn BASIC the easy way, try to pick up an MSX2 BASIC manual on ebay. They usually only cost about 2 euros and have lots and lots of information on BASIC. I still use mine from time to time, although there's not much holding the pages together after all those years!

You can also consider downloading the emulator RuMSX. As an emulator it's a little behind the other ones (like blueMSX), but the help file contains a section (Operating Systems -> MSX-BASIC) where almost all the MSX-BASIC commands are reviewed with their proper syntax. Could be very helpful until you find yourself an MSX2 BASIC book.
NYYRIKKI
msx master
Berichten: 1503
Geplaatst: 11 Januari 2005, 16:13   

MSX2 technical handbook is very good information collection for MSX1 programmer as well.

For MSX1, you may want to also read "MSX the Red book" that can be found here:
ftp://ftp.funet.fi/pub/msx/txt/programming/tredbook.arj

... it is a very good explanation about MSX1 from start to end, but as it does not explain the standards, you will end up in troubles if you just carelessly use the information it contains. It anyway explains you, how MSX works. MSX2 technical handbook contains plenty of information of standards.

Best MSX(1)-BASIC book I've seen is the one delivered with Canon V20. I also agree, that RuMSX BASIC manual is also good and blueMSX is good for coding.

Msx-Basic
msx friend
Berichten: 10
Geplaatst: 12 Januari 2005, 10:44   
THANK YOU GUYS,I HAVE ANOTHER QUESTION..
I SUPPOSE THAT EVERYONE OF YOU PLAY THE NINTENDO ENTERTAINMENT SYSTEM (NES) GAMES,,WHAT PROGRAMMING LANGUAGE THEY USED TO MAKE THESE GAMES??????????
AND THE (DOS) GAMES,,WHICH LANGUAGE THEY USED TO MAKE THESE GAMES??IS IT C++ OR I AM WRONG..

THANKS
MSX-BASIC


 
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