This page (revision-14) was last changed on 03-Feb-2023 15:21 by Roland B. Wassenberg 

This page was created on 12-Mar-2010 11:37 by Carsten Strotmann

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
14 03-Feb-2023 15:21 7 KB Roland B. Wassenberg to previous
13 23-May-2020 21:50 7 KB Roland B. Wassenberg to previous | to last
12 19-Oct-2017 19:58 7 KB Roland B. Wassenberg to previous | to last
11 19-Oct-2017 19:57 7 KB Roland B. Wassenberg to previous | to last
10 19-Oct-2017 19:43 7 KB Roland B. Wassenberg to previous | to last
9 19-Oct-2017 19:42 7 KB Roland B. Wassenberg to previous | to last
8 19-Oct-2017 19:41 7 KB Roland B. Wassenberg to previous | to last
7 19-Oct-2017 19:37 7 KB Roland B. Wassenberg to previous | to last
6 12-Mar-2010 14:28 7 KB Gromit to previous | to last
5 12-Mar-2010 14:09 7 KB Gromit to previous | to last
4 12-Mar-2010 11:41 7 KB Carsten Strotmann to previous | to last
3 12-Mar-2010 11:39 7 KB Carsten Strotmann to previous | to last
2 12-Mar-2010 11:38 7 KB Carsten Strotmann to previous | to last
1 12-Mar-2010 11:37 7 KB Carsten Strotmann to last

Page References

Incoming links Outgoing links
OSS A+ 2
OSS A+ 2

Version management

Difference between version and

At line 1 changed 2 lines
!!! OSS/A+ Version 2
!!!OSS OS/A+ Version 2.10; Copyright (C) 1981-1983 OSS, Inc.
At line 5 changed one line
\\
!!ATR image
* [OSS OS/A+ Version 2.10|OSS_OS-Aplus_v2.atr]
At line 7 changed one line
( Information from the OSS/A+ 4.0 Handbook )
!!Manuals
* [OSS OS/A+ manual|OS_A_Plus_manual.pdf] ; size: 7.2 MB ; thanks to Atarimania! :-)
* [OSS OS/A+ manual June 1983|OS_A_Plus_June_83_rev.pdf] ; size: 4.9 MB ; thanks to Atarimania! :-)
* [OSS OS/A+ bug sheet|OS_A_Plus_Bug_Sheet.pdf] ; thanks to Atarimania! :-)
At line 9 changed one line
!! Version 2 File Structure
(Information from the OSS/A+ 4.0 Handbook)
!!Version 2 File Structure
At line 14 changed one line
wrote Atari's DOS). For reasons known best to Atari, OSS were
wrote Atari's [DOS]). For reasons known best to Atari, OSS were
At line 44 changed one line
!!! DATA SECTORS
!!DATA SECTORS
At line 46 changed one line
A Data Sector is used to contain the file's data bytes. Each 128 ~[256~] byte data sector is organized to hold 125 ~[253~] bytes of data and three bytes of control. The data bytes start with the first byte (byte 0) in the sector and run contiguously up to, and including, byte 124 \[252\]. The control information starts at byte 125 \[253\]
A Data Sector is used to contain the file's data bytes. Each 128 ~[256~] byte data sector is organized to hold 125 ~[253~] bytes of data and three bytes of control. The data bytes start with the first byte (byte 0) in the sector and run contiguously up to, and including, byte 124 ~[252~]. The control information starts at byte 125 ~[253~]
At line 48 changed one line
The sector byte count is contained in byte 127 \[255\]. This value is the actual number of data bytes in this particular sector. The value may range from zero (no data) to 125 \[253\] (a full sector). Any data sector in a file may be a short sector (contain less than 125 \[253\] data bytes).
The sector byte count is contained in byte 127 ~[255~]. This value is the actual number of data bytes in this particular sector. The value may range from zero (no data) to 125 ~[253~] (a full sector). Any data sector in a file may be a short sector (contain less than 125 ~[253~] data bytes).
At line 50 changed one line
The left six bits of byte 125 \[253\] contain the file number of the file. This number corresponds to the location of the file's entry in the Directory. Directory entry zero in Directory sector $169 has a file number of zero. Entry one in Directory sector $169 has a file number one, and so forth. The file number value may range from zero to 63 ($3F). The file number is used to insure that the sectors of one file do not get mixed up with the sectors of another file.
The left six bits of byte 125 ~[253~] contain the file number of the file. This number corresponds to the location of the file's entry in the Directory. Directory entry zero in Directory sector $169 has a file number of zero. Entry one in Directory sector $169 has a file number one, and so forth. The file number value may range from zero to 63 ($3F). The file number is used to insure that the sectors of one file do not get mixed up with the sectors of another file.
At line 52 changed one line
The right two bits of byte 125 \[253\] (and all eight bits of byte 126 \[254\]) are used to point to the next data sector in the file. The ten bit number contains the actual disk sector number of the next sector. Its value ranges from zero to 719 ($2CF). If the value is zero then there are no more sectors in the file sector chain. The last sector in the file sector chain is the End-Of-File sector. The End-of-File sector will almost always be a short sector.
The right two bits of byte 125 ~[253~] (and all eight bits of byte 126 ~[254~]) are used to point to the next data sector in the file. The ten bit number contains the actual disk sector number of the next sector. Its value ranges from zero to 719 ($2CF). If the value is zero then there are no more sectors in the file sector chain. The last sector in the file sector chain is the End-Of-File sector. The End-of-File sector will almost always be a short sector.
At line 54 changed one line
!!! DISK DIRECTORY
!!DISK DIRECTORY
At line 72 changed one line
[{Image src='version2dir'}]
[{Image src='version2dir.png'}]
At line 77 changed one line
!!! VOLUME TABLE OF CONTENTS (VTOC)
!!VOLUME TABLE OF CONTENTS (VTOC)
At line 81 changed one line
The sector bit map is a contiguous string of 90 bytes, each of which contains eight bits. There are a total of 720 (90 x 8) bits in the bit map -- one for each possible sector on an 810 diskette. The 90 bytes of bit map start at VTOC byte ten ($OA). The leftmost bit ($80 bit) of byte $OA respresents sector zero. The bit just to the right of the leftmost bit ($40 bit) represents sector one. The rightmost bit (bit $01) of byte $63 represents sector 719.
The sector bit map is a contiguous string of 90 bytes, each of which contains eight bits. There are a total of 720 (90 x 8) bits in the bit map -- one for each possible sector on an 810 diskette. The 90 bytes of bit map start at VTOC byte ten ($OA). The leftmost bit ($80 bit) of byte $OA represents sector zero. The bit just to the right of the leftmost bit ($40 bit) represents sector one. The rightmost bit (bit $01) of byte $63 represents sector 719.
At line 96 changed 3 lines
!!Picture
[{Image src='OS_A_Plus_d7.jpg' width=395 height=395 }]
OSS/A+ Version 2 diskette ; thanks to Atarimania! :-)
This page (revision-14) was last changed on 03-Feb-2023 15:21 by Roland B. Wassenberg  Top