This is an HTML/ scan_fax'd version of this leaflet about disk commands and DOS error messages on the CBM/PET.
It mentions BASIC 3.0 in places - this is not an error it actually is printed that way - but those commands work with BASIC 2.0
The scans at the bottom of the page are converted fax's - sorry about quality

errors
encountered
while trying to
disk mediatape media
LOAD
a program -
DEVICE NOT PRESENT :
„ appropriate device not attached to computer or not turned on .
NOTE: before turning the disk drive on or off take care to ensure that
any diskettes are first removed.
„ addressed device doesn't correspond to accepted device number protocol
LOAD
a program -
* READ ERROR :
disk controller unable to read requested data

*FILE NOT FOUND:
requested file not on indicated drive

*DISK ID MISMATCH:
this error occurs upon failure to initialize the disk.

*DEVICE NOT READY:
an attempt has been made to access the 8050 dual drive floppy disk without any diskettes present in either drive
LOAD ERROR:
„more than 31 errors
exist in the first tape block.
„errors in exactly the
same corresponding
positions of both blocks.

STATUS ERROR
non-fatal errors of
various types.
note: obtain after
LOAD is complete by PRINT ST followed by RETURN
RUN
a program -
REDO FROM START:
„computer asked for a number and you gave it an alphabetic character .
„computer will continue to print an error mesage until correct data is entered
INPUT ERROR:
„more data is needed to satisfy program demands
„this error does not stop program execution . The computer waits for more data to be entered.
SYNTAX ERROR:
„computer cannot recognize command
„incorrect spelling or punctuation
RUN
a program -
*DEVICE NOT READY:
an attempt has been made to access the 8050 dual drive floppy disk without any diskettes present in either drive
DEVICE NOT PRESENT :
„ appropriate device not attached to computer or not turned on .
SAVE
a program -
VERIFY ERROR
stored file does not correspond with information in computer memory
SAVE
a program -
*FILE EXISTS:
file name of newly created file already exists on diskette.
*WRITE PROTECT:
write protect tap over notch on diskette prevents any data being written to disk.
*DISK ID MISMATCH:
this error occurs upon failure to initialize the disk.
*DOS MISMATCH:
this error occurs whenever a disk with wrong format is written upon.
*DEVICE NOT READY:
an attempt has been made to access the 8050 dual drive floppy disk without any diskettes present in either drive
DEVICE NOT PRESENT :
appropriate device not attached to computer or not turned on .
*NOTE : disk errors are first indicated by red light in center of disk drive.
if using BASIC 4.0 , you may obtain error messages by typing PRINT DS$ followed by RETURN.
the screen will then display the appropriate error mesage.
DISK COMMANDS
___ 40 col display ______ 80 col display ___
BASIC 3.0

SAVE"dr:fn",8
LOAD"dr:fn",8
LOAD"*",8
VERIFY"dr:fn",8
VERIFY"*",8
BASIC 4.0

DSAVE"fn",Dx
DLOAD"fn",Dx
DSAVE"*",Dx
VERIFY"dr:fn",8
VERIFY"*",8
directory :directory :
LOAD"$dr",8
LIST
DI(shifted)R Dx
DIRECTORY Dx
formatting :formatting:
OPEN 1,8,15
PRINT#1,"Nx:fn,xx"
HEADER"fn",Dx,Ixx
intialize:intialize:
(not necessary with the 8050)
OPEN 1,8,15
PRINT#1,"Ix"
OPEN 1,8,15
PRINT#1,"Ix"
error messages :error messages:
10 OPEN1,8,15
20 OPEN#1,A,B$,C,D
30 PRINT A,B$,C,D
PRINT DS$
TAPE COMMANDS
1st cassette:1st cassette:
(same as BASIC 3.0)
SAVE"fn"
LOAD"fn"
VERIFY"fn"
SAVE"fn"
LOAD"fn"
VERIFY"fn"
2nd cassette:2nd cassette:
(same as BASIC 3.0)
SAVE"fn",2
LOAD"fn",2
VERIFY"fn",2
SAVE"fn",2
LOAD"fn",2
VERIFY"fn",2
NOTE : all BASIC 3.0 commands are upwards compatible with BASIC 4.0
fn=file name supplied by user
x= dr = disk drive number (1 or 0 ) : both Dx and dr default to 0
8 = device number ( 8 for disk , 2 for second cassette , 4 for printer)
xx = two character , numeric id supplied by user
A = error message number B$ = error message C= track D = sector

All upper-case characters shown in format are essential for proper execution of command .
These must be entered from the keyboard as unshifted characters . On a Business Model they
will appear in lower case . The only execption is the short form of the DIRECTORY command
which uses a shifted "R"

REQUESTING ERROR MESSAGES : COMMODORE DISK DRIVES
Requesting the error requires execution of a program if using BASIC 3.0 or a direct command if using BASIC 4.0 . Either method causes the error to be displayed on the computer screen and resets the device error indicator
CBM Series 2001
CBM Series 3000
with
BASIC 3.0
CBM Series 8000
CBM Series 4000
with
BASIC 4.0
40 column display 80 column display
10 OPEN 1,8,15
20 INPUT#1,A,B$,C,D
30 PRINT,A,B$,C,D
PRINT DS$
where
A = error message number B$ = error message C= track D = sector
DESCRIPTION of DISK OPERATING SYSTEM (DOS) ERROR MESSAGES
fax of  error numbers and descriptions 20-22
fax of  error numbers and descriptions 23-30
fax of  error numbers and descriptions 31-64
fax of  error numbers and descriptions 65-74