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DU-V75 Installation
Logging disks; examining disk parameters
Positioning and reading
Viewing data
Writting data
Miscellanea
Examples of command use
Interpreting DU lines
: DU-V75.DOC
by Ward Christensen
with additional notes by Ron Fowler
(revised 1/23/81)
*** Installation ***
The 7.0 and later versions of DU are designed to be installed with a minimum
of trouble. In fact, in al- most all cases, no changes to the source file
should be necessary to get DU up and running. This is because DU uses the disk
paramter block of CP/M to determine the characteristics of the disk
environment. (see the dis- claimer for certain non-standard versions of CP/M
1.4).
The only parameter that should need to be changed will be the clock speed flag
at 103H. Leave this byte zero if you have a 2 mhz clock. Patch it non-zero
for 4 mhz. This is only needed for the "Z" (sleep) command.
:Logging and viewing disk parameters
L Re-logs in the current disk. You may pull out a disk, put in a new,
and "L" just to log it in.
Lx Logs in disk 'x', such as: LB
Ux Logs user 'x' for next F command. Gives '?' error if not CP/M version
2.x.
# Prints the disk parameters
Fname Print directory for file "name", then positions to its directory
sector. (Won't position under CP/M 2.x, but see = command below.)
M Dumps a map of the group allocations for files. Mn Shows which
file is allocated to group "n".
:Positioning and reading
Tnn Seek to track nn (no read)
Snn Position to sector nn, and read
Gnn Position to group nn and read.
G Shows current position
=string Ascii search, starting at current sector. <xx> hex may be imbedded, or
used alone: To find "IN 0FEH": =<db><fe> Ignores bit 7 unless <xx>
is used.
+ advance 1 sector (if below track 2, this advances to next numerical,
if 2 or >, advances based on CP/M's normal sector scrambling
algorithm, i.e. so + will get the next logical sector of the file
- backs up 1 logical sector
Note + and - may take an amount: for example, +F steps in 15 sectors. Note
also that "-" issued at the first logical sector of the disk will wrap back to
the last. Note "+" issued at last sector will wrap forward to the first.
R Reads the sector currently positioned to into memory. Note R (Read)
is implicit in the G, +, and - commands, but N-O-T in the S and T
commands (I did it because I was tired of disk reading after T command
before I had a chance to issue the S command)
< Saves current sector in a save buffer
> Gets saved buffer. < and > may be used to move a sector to another
place.
:Viewing data
V Views the current sector. (assumes ASCII data)
Vnn Views nn sectors
D Dump sector, hex + ASCII
A Dump sector, ASCII only
H Dump sector, hex only
Note all dump commands (D, A, H) may be optionally followed by a starting and
ending address:
D0,7F is the same as just D
D3,5
A20,3F
:Altering data
CHaddr,val,val,val... change hex in sector
CAaddr,char string... change ASCII in sector
NOTE that <xx> may be hex imbedded in the Ascii: ca0,OK<d><a><1a>
Use W to write changes to disk. Note that the C command echoes the
overlaid data for verification.
CHaddr-addr,byte or CAaddr-addr,byte repeats a change
W Write back the current sector (N-O-T-E may not be used after an F
command, as CP/M was used to find the file in the directory
:Miscellanea
? Gives command summary
N Resets CP/M via the BDOS. This may make it possible under some
implementations of CP/M to change the disk format (e.g., density,
sides, etc)
X Exit back to CP/M (Must press return). Ctl-c was too easy to hit over
modem lines, so I decided on 2-byte (X, CR) to exit.
P Toggle printer switch on/off
Z Sleep - causes the program to pause, such as to look at a dump. Z is
1 sec. Znn is nn tenths of a second on a 2 MHz 8080.
/ Repeats entire command. Defaults or /nn to "forever". NN may
be 2 to 65535
:Examples
Multiple commands may be separated by ";"
Any valid command string may be placed as an operand of the original DU
command, i.e.:
A>DU G0;D;G2;=OK<D><A><1A>;D
Example: the following commands will erase the b disk directory to all E5's:
lb log in b drive
g0 position to dir.
ch0-7f,e5 fill with e5
< save the sector
>;w;+;/16 restore, write, next,
repeat 16
This could be shortened to:
lb;g0;ch0-7f,e5;<
>;w;+;/16
:INTERPRETATION OF DIRECTORY DATA PRESENTED BY THE DU PROGRAM
The following explains the format of a CP/M directory entry as shown by DU,
using either the "F" (find file) command, or just doing "D" (dump) of the
directory sectors, which are located in groups 0 and 1 on a single density
disk. Sample result of "FSID.COM" command:
First 40 00534944 20202020 20434F4D 0000003A *.SID COM...:*
line || ||| | || || | |
|| ||^----hex file name-----^ || || ^file name^
|| || || || in ASCII
|| || extent-^^ ||
|| || ||
|| || file size in sectors-^^
|| ||
|| ^^-00 = file active
|| E5 = file erased
^^-displacement of line in directory sector
Second 50 33343536 3738393A 00000000 00000000 *3456789:........*
line | |
^---allocation group numbers-------^