Posted By
SVS
on 2008-02-08
13:51:25
 |  Writing CHR$(0)
Hello,
does anybody know if the command PRINT# has problems to write on disk the NULL character ($00)?
I've met some problems, maybe they come from the string where I stored the $00. I mean that it could be that a string with only $00 has null lenght?!
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Posted By
siz
on 2008-02-09
03:17:19
| Re: Writing CHR$(0)
AFAIK BASIC stores strings with a terminating null character, thus it cannot read and write chr$(0) characters. 
And yes: a string with only a chr$(0) means an empty string.
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Posted By
SVS
on 2008-02-09
04:35:44
| Re: Writing CHR$(0)
1) Does this mean that is is impossible to write a byte with $00 inside any file?
2) I've tried this: A$=chr$(0)+chr$(0): ? LEN(A$)
the result is 2.
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Posted By
Rachy
on 2008-02-09
05:02:21
| Re: Writing CHR$(0)
BASIC does not store strings in null-terminated form. You can store 0 character value in strings, also you can use PRINT# command to store it in files. I don't know what went wrong in your case, SVS.
I have just tested it with Yape in IEC mode:
OPEN1,8,1,"TEST" RINT#1,"ABC"+CHR$(0)+"DEF":CLOSE1
The content of the file is:
41 42 43 00 44 45 46 0D
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Posted By
Rachy
on 2008-02-09
05:03:02
| Re: Writing CHR$(0)
Ookay, the smiley is colon ( and P, obviously...
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Posted By
Rachy
on 2008-02-09
05:03:51
| Re: Writing CHR$(0)
Pff... 
So: colon ( : ) and P...
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Posted By
siz
on 2008-02-09
15:30:29
| Re: Writing CHR$(0)
Sorry. So my memory does not serve me well. Only the BASIC INPUT# and GET# has problems with CHR$(0): they sense it as an EOF.
I tested with this simple program:
10 A$="ABC"+CHR$(0)+"DEF"
20 PRINTLEN(A$), A$
30 OPEN1,8,1,"TEST"RINT#1,A$:CLOSE1
40 OPEN1,8,0,"TEST":INPUT#1,B$:CLOSE1
50 PRINTLEN(B$), B$
READY.
RUN
7 ABCDEF
3 ABC
READY.
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Posted By
siz
on 2008-02-09
15:31:06
| Re: Writing CHR$(0)
Oops, my : P become a smiley too...
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Posted By
SVS
on 2008-02-10
07:37:15
| Re: Writing CHR$(0)
SIZ, from my tests the CHR$(0) is not stored inside the file by PRINT#.
Infact reading data a byte a time by GET#, the resulting string is without the CHR$(0).
Example:
PRINT# "abc"+CHR$(0)+"def"
GET# B$.....A$=A$+B$ (7 times)
Result string A$ is "abcdef" (6 characters long)
Does this result to you too?
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Posted By
JamesC
on 2008-02-10
11:52:30
| Re: Writing CHR$(0)
The system has to be able to write and read CHR$(0), otherwise BASIC End-of-Line markers would be destroyed when a program was reloaded.
Are you using any custom load/save routines (including fastloaders)?
Does your program absolutely REQUIRE the CHR$(0)? Could you substitute another marker and then replace the marker upon reloading?
ie:
1300 OPEN 8,8,8,"somefile,u,r" : DO
1310 GET#8, A$, B$ : IF A$ = CHR$(255) ANB B$ = CHR$(1) THEN A$ = CHR$(0) : B$ = ""
1320 DA$ = DA$ + A$ + B$ : LOOP UNTIL ST = 64
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Posted By
TNT/BF
on 2008-02-10
14:22:37
| Re: Writing CHR$(0)
When you read CHR$(0) you need to do it this way:
...
100 GET #8,A$:IF A$="" THEN A$=CHR$(0)
...
because BASIC returns empty string for CHR$(0).
(Works on C64 at least )
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