AMSDOS Header - Revision history

Phi2x at 15:09, 26 April 2025

2025-04-26T15:09:28Z

← Older revision		Revision as of 15:09, 26 April 2025
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	\|-		\|-
	\| 9..11 \|\| Extension \|\| Unused characters are filled with space		\| 9..11 \|\| Extension \|\| Unused characters are filled with space
	\|-
	~~\| 12..15 \|\| Zero \|\| Contains all zeroes~~
	\|-		\|-
	\| 18 \|\| File type \|\| #16, unprotected ASCII version 1		\| 18 \|\| File type \|\| #16, unprotected ASCII version 1

TFM at 11:34, 24 October 2024

2024-10-24T11:34:28Z

← Older revision		Revision as of 11:34, 24 October 2024
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	This is only a summary. All details are in [[Firmware Guide]] chapter 9, page 4.		This is only a summary. All details are in [[Firmware Guide]] chapter 9, page 4.

			=== Expansion of the AMSDOS Header ===
			Some OS and DOS expanded the classic AMSDOS header:

			1. [[FutureOS Header]]:
			* Contains and icon or information text
			* File length is 24 Bit
			* Defined Loading and Autostart (expansion) RAM configuration
			* Additional file types

	[[Category:Disc Operating System]]		[[Category:Disc Operating System]]
	[[Category:Programming]]		[[Category:Programming]]

Phi2x at 17:05, 15 October 2024

2024-10-15T17:05:36Z

← Older revision		Revision as of 17:05, 15 October 2024
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	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-
	~~! Field !~~! Bytes !! Name !! Notes		! Bytes !! Name !! Notes
	\|-		\|-
	~~\| rowspan="10" \| System \|~~\| 0 \|\| User number \|\| User number, #00..#FF		\| 0 \|\| User number \|\| User number, #00..#FF
	\|-		\|-
	\| 1..8 \|\| Filename \|\| Unused characters are filled with space		\| 1..8 \|\| Filename \|\| Unused characters are filled with space

Phi2x at 09:41, 15 October 2024

2024-10-15T09:41:34Z

← Older revision		Revision as of 09:41, 15 October 2024
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	\| 12..15 \|\| Zero \|\| Contains all zeroes		\| 12..15 \|\| Zero \|\| Contains all zeroes
	\|-		\|-
	\| 18 \|\| File type \|\| #16, unprotected ~~ASCCI~~ version 1		\| 18 \|\| File type \|\| #16, unprotected ASCII version 1
	\|-		\|-
	\| 19..20 \|\| Data location \|\| Address of 2K buffer		\| 19..20 \|\| Data location \|\| Address of 2K buffer

Phi2x at 09:37, 15 October 2024

2024-10-15T09:37:57Z

← Older revision		Revision as of 09:37, 15 October 2024
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	These headers are detected by checksumming the first 67 bytes of the record. If the checksum is as expected then a header is present, if not then there is no header.		These headers are detected by checksumming the first 67 bytes of the record. If the checksum is as expected then a header is present, if not then there is no header.

	When a file without a header is opened for input a fake header is constructed in store as follows:		When a file without a header is opened for input, a fake header is constructed in store as follows:

	{\| class="wikitable"		{\| class="wikitable"

Phi2x at 09:37, 15 October 2024

2024-10-15T09:37:37Z

@@ Line 46: / Line 46: @@
 These headers are detected by checksumming the first 67 bytes of the record. If the checksum is as expected then a header is present, if not then there is no header.
-To calculate the checksum, just add all bytes from 00 up to and including byte 66 together.
+When a file without a header is opened for input a fake header is constructed in store as follows:
 This is only a summary. All details are in [[Firmware Guide]] chapter 9, page 4.

Phi2x at 09:20, 15 October 2024

2024-10-15T09:20:13Z

← Older revision		Revision as of 09:20, 15 October 2024
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	\| 17 \|\| Last block \|\| Tape only, set to 0		\| 17 \|\| Last block \|\| Tape only, set to 0
	\|-		\|-
	\| 18 \|\| File type \|\| Bit0 = Protection (set if protected)		\| 18 \|\| File type \|\| As per cassette: Bit0 = Protection (set if protected)

	Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated)		Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated)
Line 23:		Line 23:
	Bits4..7 = Version (ASCII files should be version 1, all other files should be version 0)		Bits4..7 = Version (ASCII files should be version 1, all other files should be version 0)
	\|-		\|-
	\| 19..20 \|\| Data length \|\| ~~The~~ number of data bytes in the data record~~. As per cassette~~		\| 19..20 \|\| Data length \|\| As per cassette: the number of data bytes in the data record
	\|-		\|-
	\| 21..22 \|\| Data location \|\| ~~Where~~ the data was written from originally~~. As per cassette~~		\| 21..22 \|\| Data location \|\| As per cassette: where the data was written from originally
	\|-		\|-
	\| 23 \|\| First block \|\| Set to #FF, only used for output files		\| 23 \|\| First block \|\| Set to #FF, only used for output files
	\|-		\|-
	\| rowspan="3" \| User \|\| 24..25 \|\| Logical length \|\| ~~Actual~~ file length is here~~. As per cassette~~		\| rowspan="3" \| User \|\| 24..25 \|\| Logical length \|\| As per cassette: actual file length is here
	\|-		\|-
	\| 26..27 \|\| Entry address \|\| ~~The~~ execution address for machine code programs~~. As per cassette~~		\| 26..27 \|\| Entry address \|\| As per cassette: the execution address for machine code programs
	\|-		\|-
	\| 28..63 \|\| Unused \|\| As per cassette		\| 28..63 \|\| Unused \|\| As per cassette

Phi2x at 09:16, 15 October 2024

2024-10-15T09:16:41Z

← Older revision		Revision as of 09:16, 15 October 2024
Line 3:		Line 3:
	{\| class="wikitable"		{\| class="wikitable"
	\|-		\|-
	! Bytes !! Name !! Notes		! Field !! Bytes !! Name !! Notes
	\|-		\|-
	\| 0 \|\| User number \|\| 0-15, or #E5 for deleted entries		\| rowspan="10" \| System \|\| 0 \|\| User number \|\| 0-15, or #E5 for deleted entries
	\|-		\|-
	\| 1..8 \|\| Filename \|\| Unused characters are filled with space		\| 1..8 \|\| Filename \|\| Unused characters are filled with space
Line 29:		Line 29:
	\| 23 \|\| First block \|\| Set to #FF, only used for output files		\| 23 \|\| First block \|\| Set to #FF, only used for output files
	\|-		\|-
	\| 24..25 \|\| Logical length \|\| Actual file length is here. As per cassette		\| rowspan="3" \| User \|\| 24..25 \|\| Logical length \|\| Actual file length is here. As per cassette
	\|-		\|-
	\| 26..27 \|\| Entry address \|\| The execution address for machine code programs. As per cassette		\| 26..27 \|\| Entry address \|\| The execution address for machine code programs. As per cassette
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	\| 28..63 \|\| Unused \|\| As per cassette		\| 28..63 \|\| Unused \|\| As per cassette
	\|-		\|-
	\| 64..66 \|\| Real length \|\| Length of the file in bytes, excluding the header record. 24 bit number, least significant byte first. Just a copy, not used!		\| rowspan="3" \| AMSDOS \|\| 64..66 \|\| Real length \|\| Length of the file in bytes, excluding the header record. 24 bit number, least significant byte first. Just a copy, not used!
	\|-		\|-
	\| 67..68 \|\| Checksum \|\| Unsigned sum of all bytes until this field		\| 67..68 \|\| Checksum \|\| Unsigned sum of all bytes until this field
Line 41:		Line 41:
	\| 69..127 \|\| Unused \|\|		\| 69..127 \|\| Unused \|\|
	\|}		\|}



	These headers are detected by checksumming the first 67 bytes of the record. If the checksum is as expected then a header is present, if not then there is no header.		These headers are detected by checksumming the first 67 bytes of the record. If the checksum is as expected then a header is present, if not then there is no header.

Phi2x at 09:08, 15 October 2024

2024-10-15T09:08:58Z

← Older revision		Revision as of 09:08, 15 October 2024
Line 21:		Line 21:
	Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated)		Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated)

	Bits4..7 = Version		Bits4..7 = Version (ASCII files should be version 1, all other files should be version 0)
	\|-		\|-
	\| 19..20 \|\| Data length \|\| The number of data bytes in the data record. As per cassette		\| 19..20 \|\| Data length \|\| The number of data bytes in the data record. As per cassette

Phi2x at 09:07, 15 October 2024

2024-10-15T09:07:46Z

← Older revision		Revision as of 09:07, 15 October 2024
Line 17:		Line 17:
	\| 17 \|\| Last block \|\| Tape only, set to 0		\| 17 \|\| Last block \|\| Tape only, set to 0
	\|-		\|-
	\| 18 \|\| File type \|\| Bit0 = Protection (set if protected) ; Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated) ; Bits4..7 = Version		\| 18 \|\| File type \|\| Bit0 = Protection (set if protected)

			Bits1..3 = File contents (0:BASIC, 1:Binary, 2:Screen image, 3:ASCII, 4..7 are unallocated)

			Bits4..7 = Version
	\|-		\|-
	\| 19..20 \|\| Data length \|\| The number of data bytes in the data record. As per cassette		\| 19..20 \|\| Data length \|\| The number of data bytes in the data record. As per cassette