Posted By
Charlemagne
on 2019-03-31
14:12:57
|  Puzzling about OPEN
Hello,
After reading about OPEN, I am mixed up with it:
1.: OPEN as general: "OPEN filenumber, unitnumber, channelnumber, stringexpression"
- filenumber: 1..255
- unitnumber: 0..15 (0: keyboard, 1: casette, 2: modem, 4/5: printer, 8-11: disk)
- channelnumber: 0..15 (eg.: unit=1 (casette): 0=input, 1=output, 2=output+EOT)
- stringexpression: filename
2.: OPEN as a file open: "OPEN filenumber, unitnumber, channelnumber, stringexpression"
- filenumber, unitnumber is just like as above
- channelnumber: (if unit=8) 2..14 (WHAT IS THIS???)
- stringexpression: "name,type,mode"
- - name: filename
- - type: PRG/SEQ/USR/REL = P/S/U/R
- - mode: READ/WRITE = R/W
What does the data-channel mean exactly? I know the 15 means the command-channel.
The another question about OPEN is that: "How do you handle files in assembly?"
$B8 = file-number
$B9 = open-mode
$BA = unit number
$BB = start of the command string
$B7 = the length of the command
So how do you create a new file on the disk and how do you write bytes into it in assembly?
Thanks!
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Posted By
Charlemagne
on 2019-03-31
03:01:20
| Re: Puzzling about OPEN
Thank you siz, it seems to be good.
What do you think about ROMSave by siz? 
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Posted By
SVS
on 2019-04-01
11:29:36
 | Re: Puzzling about OPEN
Some more info if can help:
CHANNELNUMBER: is used to tell the device how to manage the data transfer. 0: means load binary data from device to memory; 1: save binary data from memory to device; 15: send a commands to device.
These values are involved into buffer management too, especially when you have more opened files.
MODE: don't forget the convenient "A" mode that allows to append data to an existing SEQ/USR file without to read all the current data and then re-save all them.
SYNTAX: If you code a program in assembly, remember that you must use the DOS syntax that is different than the BASIC syntax. In short words you have to send to the unit a single string like:
"xy:zzzzzzz" where x is the command (1 letter), y is the unit (0 or 1), zzzzz is the filename. For example:
BASIC: SCRATCH "myfile"
DOS: "S0:myfile"
Le me know
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Posted By
Charlemagne
on 2019-04-02
02:52:44
| Re: Puzzling about OPEN
Thank you SVS,
eg.:
10 OPEN 1,8,2,"HELLO,SEQ,WRITE":REM OPEN 1,8,2,"HELLO,S,W"
20 PRINT#1,"WORLD";CHR$(13);
30 CLOSE 1
Channel (if unit=8..11):
- 0: save
- 1: load
- 2..14: data
- 15: command
What is the difference between:
1.: 10 OPEN 1,8,2,"HELLO,SEQ,WRITE"
and
2.: 10 OPEN 1,8,3,"HELLO,SEQ,WRITE"
?
So you cannot use two different files on the same data channel(?)
For example:
10 OPEN 1,8,2,"HELLO,SEQ,WRITE": OPEN 2,8,2,"WORLD,SEQ,WRITE"
I haven't read about "Append", yet.
DOS syntax is different? I don't think so, because...
http://codebase64.org/doku.php?id=base:writing_a_file_byte-by-byte
But, in that case when you use random files (not sequential), the syntax is really different, in BASIC, too:
10 OPEN 15,8,15: OPEN 1,8,2,"#": REM Open Pseudo-file
20 PRINT#15,"B-R:";2,0,18,0: REM Reading BAM
30 FOR I=0 TO 255
40 GET#1,X$: PRINT X$;
50 NEXT I
60 CLOSE 1: CLOSE 15
http://codebase64.org/doku.php?id=base:reading_a_sector_from_disk
By the way ROMSave saves files with SAVE ($FFD8 -> $F194), so siz doesn't save ROMs with writing files. He only sends some commands to the command channel, such like "M-R" and "M-W".
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Posted By
SVS
on 2019-04-02
03:03:10
| Re: Puzzling about OPEN
>>So you cannot use two different files on the same data channel(?)
For example:
10 OPEN 1,8,2,"HELLO,SEQ,WRITE": OPEN 2,8,2,"WORLD,SEQ,WRITE"
I suppose you obtain an error by using the same channelnumber because it is already in use.
>>DOS syntax is different? I don't think so, because...
I was referring to the fact that you always have to set the unit number (standard is 0), for example "N0:diskname" instead of "N:diskname"
>>20 PRINT#15,"B-R:";2,0,18,0: REM Reading BAM
It is recommended to use "U1" or "UA" instead of "B-R", I don't remember exactly the reason, maybe for a pointer matter.
Greetz
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Posted By
Charlemagne
on 2019-04-02
07:57:21
| Re: Puzzling about OPEN
Yes, you are right SVS, it's hard two streams to flow in the same course...
I have just read about "U1 or UA" and "U2 or UB"... ...well the difference between "U1 or UA" and "B-R" is that "U1 or UA" takes no notice of the buffer-pointer (the first byte of a block).
But I don't understand why does "M-Rxy" (where x=low byte of address, y=high byte of address) work in ROMSave... ...because the syntax is: "M-R:" (with colon), but you may be right again and the syntax is different in assembly a little bit.
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Posted By
SVS
on 2019-04-02
08:42:23
| Re: Puzzling about OPEN
Hi again,
I've investigated about the difference between B-R and U1.
The B-R (and mirrored the B-W) takes the first byte of the sector as number of valid bytes to be read. Then if a sector contains, for example, "03 41 51 6A F8 ..." it will transfer only 41 51 6A (3 bytes). This way can be useful for some customized data structures, anyway each sector allowing 1 less byte of data. The U1 on the contrary transfers the whole sector of data starting from the first byte.
About the matter of the ":". It is a flag for the DOS to indicate the end of the command. You can send the command as long as you want, it acknowledges only the first character (for ex. N can be NEW, NE, N, but even NEWAGE ). When found the ":" it understands that the command name is finished and the following data (if any) are the parameters.
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