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Forums > CSDb Discussions > sequential file or seq file
2021-04-02 13:25
maestro

Registered: Mar 2004
Posts: 696
sequential file or seq file

what is a seq file? does it stand for sequential file?

how can i copy a *.seq file from a floppy disk?

i have a disk at present. tried copying the whole disk and all i get is red blocks. wont copy the disk. no image made. so i tried copying the files one by one. all files copied apart from the seq file? is it important? if it isnt why is it on the disk? it must mean something or does it not? do i not need it?

thanks for any help
2021-04-02 13:50
hedning

Registered: Mar 2009
Posts: 3174
Aren't you in The Transfer Team? :O
2021-04-02 14:12
maestro

Registered: Mar 2004
Posts: 696
i am in the transfer team. but i havent encountered this issue before and i certainly dont know everything about the commodore 64.
2021-04-02 14:19
tlr

Registered: Sep 2003
Posts: 1443
A SEQ file is indeed a sequential file. This and and a USR file is mostly the same as a PRG file, i.e just a list of bytes. For PRG files there is a convention that the first two bytes contain the load address. This may or may not be true for SEQ or USR files.

A SEQ (or USR) file can usually be copied by a normal file copier.

REL files are however very different.
2021-04-02 18:16
Krill

Registered: Apr 2002
Posts: 1835
Quoting tlr
A SEQ (or USR) file can usually be copied by a normal file copier.
Not so sure about USR files, though. USR mostly means "anything goes", and the most prominent use for it are GEOS VLIR files. Certainly not file-copyable with regular tools.

(As an aside, earlier development versions of Transwarp V0.64 had USR files. And there are no track/sector links, so also not easily file-copyable without knowing the allocation scheme.)
2021-04-02 19:18
Groepaz

Registered: Dec 2001
Posts: 9790
the only difference between usr/seq/prg is one byte in the directory entry. what you can do with one, you can do with the other. everything else is by convention/interpretation.
2021-04-02 19:49
Krill

Registered: Apr 2002
Posts: 1835
Quoting Groepaz
the only difference between usr/seq/prg is one byte in the directory entry. what you can do with one, you can do with the other. everything else is by convention/interpretation.
Why, of course. Can always violate conventions and do whatever. :) But i guess the point was about regular, conventional uses of different filetypes.
2021-04-02 20:40
Groepaz

Registered: Dec 2001
Posts: 9790
Yes, and then the answer is that they are the same, and have the same structure. GEOS is one of the few exceptions to that rule :)
2021-04-03 08:53
Krill

Registered: Apr 2002
Posts: 1835
Quoting Groepaz
Yes, and then the answer is that they are the same, and have the same structure. GEOS is one of the few exceptions to that rule :)
The disk mentioned in the OP may or may not be one of those exceptions, though.

So i guess some further analysis is in order to see why only the SEQ file produces read errors. Could be non-standard file layout, some special (non-GCR) low-level format for that file, but of course, could also simply be broken sectors.
2021-04-03 12:44
Silver Dream !

Registered: Nov 2005
Posts: 54
Quote: Quoting Groepaz
the only difference between usr/seq/prg is one byte in the directory entry. what you can do with one, you can do with the other. everything else is by convention/interpretation.
Why, of course. Can always violate conventions and do whatever. :) But i guess the point was about regular, conventional uses of different filetypes.


I'd assume the same. The filetype is a part of file's metadata. Somewhat similar to how we widely expect a certain file content, depending on how the name of the file ends in current machines (yes, I know this is brain-dead). Here it is like a predefined set of possible name endings. I presume GEOS' VLIR could be built on top of any type but they reasonably chose the one with least connotations/expectations about the content/format. Whenever I see "PRG" I expect it to be a "loadable" file, which contains two-byte load address. Seeing "SEQ" means to me sequential data. Something that has to be OPEN() and read from rather than LOADed. I don't expect it to have two-byte load address. And "USR" means custom format - you (or your program) have to know how to use it. Obviously and as mentioned here that's only a convention because technically there's nothing special about those types. Similar to how changing how the file's name ends doesn't change anything about the file itself in - say - GNU/Linux
2021-04-03 12:56
Groepaz

Registered: Dec 2001
Posts: 9790
And it wasnt actually uncommon for commercial programs to use USR for whatever data or executables even - as a poor mans "protection" :)
 
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