File systems - Revision history

Mizapf: /* Volume Information Block (HFDC) */

2023-08-31T20:50:40Z

Volume Information Block (HFDC)

← Older revision		Revision as of 20:50, 31 August 2023
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	\|-		\|-
	\|}		\|}

	~~BS = Buffered head stepping (one bit, 0 or 1)~~

	The W,I,N values may be present after initial formatting. Usually they are replaced by the given settings.		The W,I,N values may be present after initial formatting. Usually they are replaced by the given settings.

	'''Reserved AUs''': ~~when multiplied~~ by 64 (0x40), declares the start AU for file contents. For instance, with a value of 0x15, file contents are stored at AUs 0x0540 and higher.		'''Reserved AUs''' (0-255): Value is divided by 64 (0x40) and declares the start AU for file contents (0-16320). For instance, with a value of 0x15, file contents are stored at AUs 0x0540 and higher.

	There are 114 slots for pointers to subdirectories (from 0x1c to 0xff, 2 bytes each), so this is the maximum number of subdirectories in a directory.		There are 114 slots for pointers to subdirectories (from 0x1c to 0xff, 2 bytes each), so this is the maximum number of subdirectories in a directory.

			==== Special MFM parameters ====

			'''Step speed''' (0-255): Controllers like the HDC9234 on the HFDC card use the value for step timing. The number is controller-specific.

			'''Reduced write current''' (0-255): Value is divided by 8 and indicates the cylinder number (0-2040) starting from which the write current in the write head is reduced.

			'''BS''' = Buffered head stepping (one bit, 0 or 1): Some drives allow for fast stepping by increasing a step counter and then performing a fast, single seek.

			'''Write precompensation''' (0-127): Value is divided by 16 and indicates the cylinder number (0-2032) starting from which the timing of the flux writing is changed.

	=== Volume Information Block (SCSI) ===		=== Volume Information Block (SCSI) ===

Mizapf: /* Volume Information Block */

2016-10-08T12:06:33Z

Volume Information Block

← Older revision		Revision as of 12:06, 8 October 2016
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	\|-		\|-
	! 00		! 00
	\| rowspan="5" colspan="2" \| Volume name.		\| rowspan="5" colspan="2" \| Volume name
	\| rowspan="5" class="descr" \| May not contain a dot (".") because this is used as the path separator. Padded with spaces.		\| rowspan="5" class="descr" \| May not contain a dot (".") because this is used as the path separator. Padded with spaces.
	\|-		\|-

Mizapf: /* Volume Information Block (HFDC) */

2016-09-19T19:59:24Z

Volume Information Block (HFDC)

← Older revision		Revision as of 19:59, 19 September 2016
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	\|-		\|-
	! 1A		! 1A
	\| colspan="4" \| ~~Sector~~ number of DSK1 emulation file		\| colspan="4" \| AU number of DSK1 emulation file
	\|-		\|-
	! 1C		! 1C

Stefan Haubenthal: Category

2015-07-17T18:36:10Z

Mizapf: /* File Descriptor Records */

2015-05-01T21:34:52Z

File Descriptor Records

← Older revision		Revision as of 21:34, 1 May 2015
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	\|-		\|-
	! 12		! 12
	\| colspan="2" \| Level 3 record count		\| colspan="2" \| Level 3 record count (little-endian)
	\|-		\|-
	! 14		! 14

Mizapf: /* References */

2015-05-01T21:34:01Z

References

← Older revision		Revision as of 21:34, 1 May 2015
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	== References ==		== References ==

	* Myarc, Inc.: ''Hard and Floppy Disk Controller / Users manual''		[1] Myarc, Inc.: ''Hard and Floppy Disk Controller / Users manual''
	* Western Horizon Technologies: ''Small Computer Systems Interface Host Adapter Card / Software Interface Specification'', 1993
			[2] Western Horizon Technologies: ''Small Computer Systems Interface Host Adapter Card / Software Interface Specification'', 1993

Mizapf: /* File Descriptor Records */

2015-05-01T21:33:07Z

File Descriptor Records

← Older revision		Revision as of 21:33, 1 May 2015
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	The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used. According to [1], the Extended Record Length field defines the length of records of data files when the Logical Record Length field (offset 0x11) is 0.		The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used. According to [1], the Extended Record Length field defines the length of records of data files when the ''Logical Record Length'' field (offset 0x11) is 0.

	The '''File status flags''' are defined as follows:		The '''File status flags''' are defined as follows (see also [[TIFILES format]]):

	{\| class="tfiflags"		{\| class="tfiflags"
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	\|}		\|}

	~~Bytes >E~~ and ~~>F The number of 256~~ byte ~~records allocated on level 2~~.		The '''EOF offset''' is the location in the last sector where the EOF marker is found. Only variable length data files have an EOF marker (0xff). For program files and fixed length files this field points to the first byte after the file contents. If the EOF offset contains 0, the last sector is completely filled with data.

	~~Byte >10 Contains~~ the ~~EOF offset within the highest physical AU for variable~~ length ~~records and program files.~~		To recreate the actual file length,

	~~Byte >11 Contains~~ the ~~logical record size in~~ bytes~~. For variable length records this byte contains~~ the ~~maximum permissible record size~~.		* the total number of sectors must be multiplied by 256
			* the number of bytes past the EOF marker must be subtracted (if the offset is not 0).

	~~Bytes >12 and >13 Contain~~ the number of ~~records allocated on level 3. For variable length records these bytes will contain~~ the ~~number of level 2 records actually used. NOTE: these bytes are in~~ the ~~reverse order.~~		That is, if the number of sectors is 10 and the EOF offset is 36, the file length is (10*256) - (256-36) = 2340. If the EOF offset is zero, we get the full 2560 bytes.
	~~The '''Level 3 record count'''~~ (~~>12 and >13~~) ~~specifies the number of [[records]] in [[data files]]; this means the number of times you can execute an INPUT operation on that file~~. ~~Note that~~ the ~~value~~ is ~~specified in '''little-endian''' format~~, ~~untypically for~~ the ~~TI architectures, with the lower byte first, then the higher byte: The count calculates as C = BBAA with BB at offset 0x13 and AA at offset 0x12~~.

	~~Bytes >14 to >1B These bytes were reserved for future expansion, and will always be 0 on a disk formatted with the TI Disk Manager Module..~~

	~~Bytes >1C~~ to ~~>FF contain blocks~~ of ~~three~~ bytes ~~which indicate~~ the ~~clusters which have been allocated~~ for the ~~file~~.		The '''Level 3 record count''' (offset 0x12 and 0x13) specifies the number of [[records]] in [[data files]]; this means the number of times you can execute an INPUT operation on that file. In the case of fixed length records, the field "Number of Level-3 records" contains the highest record actually written to. If the last sector is filled as far as possible, we have

			:''L3 = Records/Sector * Total number of sectors''

			This number is required to determine the highest record number, especially if the last sector is not filled completely.

			In the case of variable length records, it contains the highest sector actually written to and should therefore be equal to the field "Total number of sectors".

			For program files, 0x0000 is usually found in this field.

			'''NOTE''': The bytes in this field are in '''reverse order''' (little-endian).


			The '''Creation''' and '''Update time specification''' are two 16-bit words, the bits having the following meaning:

			* hhhh.hmmm.mmms.ssss
			* yyyy.yyyM.MMMd.dddd

			With only 5 bits for seconds, the timestamp has a resolution of 2 seconds. The years reach from 1970 (values 70..99) to 2069 (values 0..69).

			These bytes were reserved for future expansion, and will always be 0 on a disk formatted with the TI Disk Manager Module.


	The '''Data chain pointers''' are used to refer to sections on the disk where fragments of the file will be found. There is always at least one data chain pointer; if there are more, the file is ''fragmented''.		The '''Data chain pointers''' are used to refer to sections on the disk where fragments of the file will be found. There is always at least one data chain pointer; if there are more, the file is ''fragmented''.
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	This means: The file occupies the sectors >0036 (sector 0), >0037 (sector 1), >0044 (sector 2), ... >041b (sector 16). Note that N does not provide the length of the current chain element but the total number of read sectors after reading this chain element. Counting from 0, and together with the directory entry, we have		This means: The file occupies the sectors >0036 (sector 0), >0037 (sector 1), >0044 (sector 2), ... >041b (sector 16). Note that N does not provide the length of the current chain element but the total number of read sectors after reading this chain element. Counting from 0, and together with the directory entry, we have

	:''The number of sectors which a file occupies on the disk is N<sub>last</sub>+2''		:''The number of sectors which a file occupies on the disk is N<sub>last</sub>+1''

	Or you may want calculate the intervals as follows:		Or you may want calculate the intervals as follows:

Mizapf: /* File Descriptor Records */

2015-05-01T21:22:11Z

File Descriptor Records

@@ Line 195: / Line 195: @@
-The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used, and whether indeed both bytes (0x0A, 0x0B) are significant; maybe the byte at 0x0A is assumed to be zero. In any case we can say that the record length calculates as RL = AABBCC, where AA is at 0x0A, BB is at 0x0B, and XX is at 0x11.
+The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used. According to [1], the Extended Record Length field defines the length of records of data files when the Logical Record Length field (offset 0x11) is 0.
-Byte >0C The file status flags are as follows, where Bit O is the LSB:
+The '''File status flags''' are defined as follows:
 Bytes >E and >F The number of 256 byte records allocated on level 2.

Stephen Shaw: /* File Descriptor Records */ extend the description of FDRs; noted TI none-use of bytes >14 to >1B

2015-04-20T18:02:47Z

File Descriptor Records: extend the description of FDRs; noted TI none-use of bytes >14 to >1B

@@ Line 197: / Line 197: @@
 The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used, and whether indeed both bytes (0x0A, 0x0B) are significant; maybe the byte at 0x0A is assumed to be zero. In any case we can say that the record length calculates as RL = AABBCC, where AA is at 0x0A, BB is at 0x0B, and XX is at 0x11.
-The '''Level 3 record count''' specifies the number of [[records]] in [[data files]]; this means the number of times you can execute an INPUT operation on that file. Note that the value is specified in '''little-endian''' format, untypically for the TI architectures, with the lower byte first, then the higher byte: The count calculates as C = BBAA with BB at offset 0x13 and AA at offset 0x12.
+Byte >0C The file status flags are as follows, where Bit O is the LSB:
 The '''Data chain pointers''' are used to refer to sections on the disk where fragments of the file will be found. There is always at least one data chain pointer; if there are more, the file is ''fragmented''.

Mizapf: /* File Descriptor Records */

2015-03-05T11:16:50Z

File Descriptor Records

← Older revision		Revision as of 11:16, 5 March 2015
Line 197:		Line 197:
	The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used, and whether indeed both bytes (0x0A, 0x0B) are significant; maybe the byte at 0x0A is assumed to be zero. In any case we can say that the record length calculates as RL = AABBCC, where AA is at 0x0A, BB is at 0x0B, and XX is at 0x11.		The '''Extended record length''' field (offset 0x0A) is used for record lengths beyond 255; up to 255 bytes the length is given by the byte at offset 0x11. The HFDC introduced this field, but it is unknown whether it was ever used, and whether indeed both bytes (0x0A, 0x0B) are significant; maybe the byte at 0x0A is assumed to be zero. In any case we can say that the record length calculates as RL = AABBCC, where AA is at 0x0A, BB is at 0x0B, and XX is at 0x11.

	The '''Level 3 record count''' specifies the number of [[records]] in [[data files]]; this means the number of times you can execute an INPUT operation on that file. Note that the value is specified in '''little endian''' format, ~~that is~~, with the lower byte first, then the higher byte: The count calculates as C = BBAA with BB at offset 0x13 and AA at offset 0x12.		The '''Level 3 record count''' specifies the number of [[records]] in [[data files]]; this means the number of times you can execute an INPUT operation on that file. Note that the value is specified in '''little-endian''' format, untypically for the TI architectures, with the lower byte first, then the higher byte: The count calculates as C = BBAA with BB at offset 0x13 and AA at offset 0x12.

	The '''Data chain pointers''' are used to refer to sections on the disk where fragments of the file will be found. There is always at least one data chain pointer; if there are more, the file is ''fragmented''.		The '''Data chain pointers''' are used to refer to sections on the disk where fragments of the file will be found. There is always at least one data chain pointer; if there are more, the file is ''fragmented''.

← Older revision		Revision as of 18:36, 17 July 2015
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	[2] Western Horizon Technologies: ''Small Computer Systems Interface Host Adapter Card / Software Interface Specification'', 1993		[2] Western Horizon Technologies: ''Small Computer Systems Interface Host Adapter Card / Software Interface Specification'', 1993

			[[Category:Programming]]