A Reference Guide to DU (Disk Utility) An "Impatient User's Guide" to DU (Disk Utility), a famous disk fixer from the public domain libraries. Prepared for The User's Guide Magazine, Vol.1, No.4 June 1983 (pages 53-63) by Kelly Smith (TUG Contributing Editor) from the original program and documentation by Ward Christensen, prolific contributor to the world of public domain CP/M software. For more information on this article and others like it, contact The User's Guide to CP/M Systems & Software, Box 3050, Stanford, VA 94305, (415) 851-7352. TUG is published every two months, $18 US, $24 outside US (add $10 for first class delivery anywhere). Introduction DU is a comprehensive "disk diddler" utility that allows a user to examine and modify ANY portion of a CP/M-80 (Version 2.0 or greater) disk at the "byte level". An "On-Line Help" facility is included (just press the '?' key followed by RETURN) should you forget the extensive command set (typically single keyboard entries, terminated with a RETURN key). A word of caution to the novice user...it is possible to DU a disk to death! That is, casual modification of portions of the CP/M-80 operating system data tracks is usually destructive to the proper operation of the "copy" of CP/M on the modified disk. Use particular care when writing your modifications back to disk! DU is an invaluable tool for recovery of "bombed directories", modification of CP/M "run time" parameters, or even making a "backup" of your disk directory and preserving it someplace "in reserve" on your disk...the possibilities are NOT LIMITED by DU! The best part is that it was provided FREE to the public domain (may be freely used and given away) by Ward Christensen, and even includes source code for your detailed examination and/or customization (when customizing public domain software, your "on- your-own" however...don't expect "hand-holding" from the original author when you "write on their wall"!). So before you go out and BUY a functionally identical software package (Gads! I would love to name names!!!), take a look at DU first. You wont't find a better program for the money! Thank you again Ward, for yet another major contribution to the CP/M software user community! So without further ado, here is your User's Guide to DU (poetic!): Index 1.0 Installation. 2.0 Usage. 2.1 Commands, by Function (Quick Reference). 2.2 Alphabetic Command Summary. 3.0 Usage Notes. 3.1 Multiple Commands. 3.2 Dump Commands. 3.3 Logging in Disk. 3.4 Sector Buffers. 4.0 Interpreting CP/M Directory Data. 4.1 Single Density. 4.2 Double Density. 5.0 DU Usage Examples 5.1 Erased Program Recovery 5.2 Modifying a Disk for "Program Autoload" 5.3 Finding and Modifying Program Data Quickly 5.4 A "Poor Man's" Disk Test 1.0 Installation DU (Disk Utility), Versions 7.0 and later, are designed to be installed with a minimum of trouble. In fact, in almost all cases, no changes to the source file should be necessary to get DU "up and running". Yes! 8080 source code is available if you want it from various RCPM systems as well as directley from the CP/M User's Group library (or you may contact the CPMUG care of: Lifeboat Associates, 1651 Third Avenue, New York. N.Y. 10028). The only requirement for usage of DU, is that you must be running in a CP/M-80 Operating System environment of "vintage" 2.0 (or greater). This is because DU uses the disk parameter block incorporated in the latest releases of Digital Research's CP/M-80 to determine the characteristics of the disk environment. Note also, that earlier versions of DU supported only the standard 8 inch "distribution standard" IBM 3740 type diskette, running CP/M-80 version 1.4 and in some cases did not work for certain "non-standard" versions of CP/M-80 (i.e., CDOS from Cromemco, and some implementations of CP/M-80 from Lifeboat Associates). The only parameter that you might need to change, will be the CPU clock speed flag at address 103H (when DU is loaded into system memory). Leave this byte zero if you have a 2 MHz clock. "Patch" it non-zero (change the address content to 0FFH) for 4 MHz (refer to your Digital Research DDT (Dynamic Debugging Tool) documentation if you are unfamilier with modification of program files, and "patching" techniques). This is only needed for the "Z" (sleep) command. An alternative is just to use larger numbers when running DU with a computer system clock rate of 4MHz or greater. 2.0 Usage An initial command string may optionally be placed as an operand of the DU command at the CP/M system user command level, i.e.: A>DU G0;D;G2;=OK<1A>;D For example, if you want to only 'MAP' the disk and then exit, you would enter at your console keyboard: A>DU M;X The DU program would then respond with the diskette 'MAP' (actually a display of the diskette Group Allocations), as shown in the following example 'MAP' of a Compupro 8/16 System diskette: DISK UTILITY ver 7.7 Universal Version Type ? for help Type X to exit 0004-0005 00 COPY .COM 00 : 0006-000D 00 WS .COM 00 000E-0010 00 DDT .COM 00 : 0011-0018 00 FMTMEM .COM 00 0019-001A 00 FORMAT .COM 00 : 001B-001B 00 CONV .COM 00 001C-001C 00 CRCK .COM 00 : 001D-001D 00 CROSSREF.COM 00 001E-001E 00 D .COM 00 : 001F-0021 00 DU .TXT 00 0022-0025 00 PIP .COM 00 : 0026-0026 00 XDIR .COM 00 0027-0027 00 FILE-XT2.COM 00 : 0028-002E 00 RMAC .COM 00 002F-0033 00 LINK .COM 00 : 0034-0034 00 EXEC .COM 00 0035-0035 00 SYSGEN .COM 00 : 0036-0036 00 FMAP .COM 00 ~ ~ | The diskette 'MAP' shown here is "edited" for brevity! | ~ ~ | .-- Group Allocation Number | ~ | .-- Filename ~ | | | .-- Filetype | ~ | | | .-- Extent Number ~ | | | | | .-- User Number | ~ | | | | | ~ 020F-020F 00 PBIOS .ASM 03 : 0210-0216 01 ALIENS .COM 00 0217-0218 00 PBIOS .ASM 03 : 0219-0219 00 MOVCPM .COM 00 021A-021A 00 MNTR .DOC 00 : 021B-021C 00 PRNT .DOC 00 021D-0220 00 REQ'D-SW.DOC 00 : 0221-0228 00 SW-DEF .TXT 00 0229-0230 00 SW-DEF .TXT 01 : 0231-0238 00 SW-DEF .TXT 02 0239-023E 00 MOVCPM .COM 00 : 023F-0241 00 FORMAT .ASM 00 0242-0242 00 FORMAT .ASM 01 : 0243-0247 ++FREE++ 0248-024B 00 PBIOS .ASM 04 : 024C-0253 00 SETATR .ASM 00 0254-0254 00 PBIOS .ASM 04 : 0255-0257 ++FREE++ G=0000:00, T=4, S=1, PS=0 A> Once DU is running, it will display the character ':' as the command level prompt, and expects single-letter commands much like DDT. For ease of use, multiple commands may be placed on one line, separated by ';'. In addition, a given command or string of commands may be repeated, either indefinitely (until Control-C (shown from now on as '^C') is pressed), or a given number of times. To avoid an accidental ^C from dropping out of DU, only an explicit 'X' command will exit DU. 2.1 Commands, by Function (Quick Reference) Help: ? Request help. Example: :? Operands in brackets [...] are optional Numeric values: 'n' are decimal, 'x' hex +[n] step in [n] sectors; -[n] step out [n] sectors # print disk parameters for curr drive. =xxx search for ASCII xxx from curr sector. Caution: upper/lower case matters. Use for hex: To find "IN 0" use: =<0> or "(tab)H,0(CR)(LF)" use: =<9>H,0 < save current sector into mem. buff. > restore saved sector ? give help A[ff,tt] ASCII dump (Type any char. to continue) C Change: CHaddr,byte,byte... (hex) or CAaddr,data... (Ascii) Allowed for imbedded hex. or CHfrom-thru,byte e.g. ch0-7f,e5 or CAfrom-thru,byte D[ff,tt] Dump (hex+ASCII) Fn.t Find file Gnn CP/M Allocation Group nn H[ff,tt] hex dump L Log in drive Lx Log in drive x M[nn] Map [from group nn] (Type any char. to continue) N New disk P Toggle printer switch Q Quiet mode (no msgs) R Read current sector Snn Sector nn Tnn Track nn Unn Set User nn for Find command (CP/M-2 only) V[nn] View [nn] ASCII sectors W Write current sector X Exit program Y Yank current sector into sequential memory Z[nn] Sleep [nn tenths] /[nn] Repeat [nn (decimal) times] (Type any char. to continue) Cancel a function with C or Ctl-C. Suspend output with S or Ctl-S. Separate commands with ";". Example: g0 +;d;z#20;/ would step in, dump, sleep 2 sec, and repeat until control-c typed. All "nn" usage except "/", "T", and "S" are HEX. Use #nn for decimal. See DU.DOC for complete examples. Positioning: Keeping "track" (literally!) of where your are on a disk is indicated by a terse display (e.g., G=009C:04, T=43, S=5, PS=4). To best illustrate the display (and most importantly, what it means), just enter the following command: :+;/ <-- advance to the next sector and repeat forever... And the Group, Track, Logical Sector, and Physical sector "assignments" will incrementally be displayed for your entire disk continuously (use ^C to quit). The "meaning" (and an example display), is as follows: .-- Group Allocation Number | .-- Sector Block Number (always 128 bytes) | | .-- Physical Track | | | .-- Logical Sector | | | | .-- Physical Sector | | | | | G=009C:01, T=43, S=2, PS=1 G=009C:02, T=43, S=3, PS=2 G=009C:03, T=43, S=4, PS=3 G=009C:04, T=43, S=5, PS=4 G=009C:05, T=43, S=6, PS=5 G=009C:06, T=43, S=7, PS=6 G=009C:07, T=43, S=8, PS=7 G=009C:08, T=43, S=9, PS=24 G=009C:09, T=43, S=10, PS=25 G=009C:0A, T=43, S=11, PS=26 G=009C:0B, T=43, S=12, PS=27 G=009C:0C, T=43, S=13, PS=28 G=009C:0D, T=43, S=14, PS=29 G=009C:0E, T=43, S=15, PS=30 G=009C:0F, T=43, S=16, PS=31 <-- end of 2K Group Number 009C G=009D:00, T=43, S=17, PS=48 <-- a new Group Allocation number starts G=009D:01, T=43, S=18, PS=49 after Sector Block Number 16 (0F HEX) ~ ~ (but may be different for YOUR DISK!) | etc., etc., etc., | Positioning therefore, is done by Group (Gnn), Track (Tnn), or Sector (Snn) movement commands as follows: Gnn By allocation group. Example: :g0 G=0000:00, T=4, S=1, PS=0 Tnn By track. Snn By sector. +nn Move ahead nn sectors. -nn Move back nn sectors. I/O: R Reads sector. W Writes sector. < Puts current sector "away" into a buffer. > Recalls previously saved sector. Displaying: G Shows current group, track, sector. M Maps the disk (file group allocations). or, Mxx Map starting at group xx D Dump the sector (Hexadecimal and ASCII display). A Dump sector in ASCII. H Dump sector in hexadecimal. Vnn Views (like CP/M TYPE) nn sectors. # Shows disk parameters, also the number of sectors stacked and used via '<<' and '>>'. Example: :# Disk Information: Tracks: 154 Sec/trk: 64 Grpsize: 16 (sectors per group) Tot grps: 599 Dir entries: 256 Sys tracks: 4 Changing: CHnn,val Change data in hexadecimal. CAnn,val Change data in ASCII ( with escape to hexadecimal). N Insert new disk. Unn Change user directory number to nn. Searching: Fname Find a file in the directory. F Find next occurrence (extent) of same name. =aaaa Scan for aaaa (in ASCII) from current sector on. Miscellaneous: Znn Sleep (nn tenths of a second) such as to allow viewing data before it scrolls off. Lx Log in disk x. P Turn on/off printer output toggle. Q Before any command does it "quietly". X Exit to CP/M. /nn Repeat previous command nn times (indefinitely if nn omitted). 2.2 Alphabetic Command Summary # Prints the disk parameters. + Advance 1 sector (if below track 2, this advances to next numerical, if 2 or greater, 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, +15 steps in 15 sectors. / Repeats entire command. Defaults to "forever". or, /nn nn may be 2 to 65,535. < Saves current sector in a save buffer, and also resets buffer pointer used by '<<' and '>>'. << Saves current sector, bumps memory pointer. Thus subsequent '<<' saves "next" buffer in memory. Use '<' to reset, or '>>' to sequentially retrieve the buffers, such as to move several sectors from one place on disk to another, or to another disk, or just to memory (stored at 2000H where DDT can be used to subsequently access them). =string Ascii search, starting at current sector. hex may be imbedded, or used alone: To find "IN 0FEH": = Note: ignores bit 7 unless is used. Since ";" is a command delimiter, you have to use <3B> to search for a ";". Also, since "<" is a hex-escape character, use << to means a single "<". Also note that the special symbol "@" contains the displacement at which the match occurred. It may thus be subsequently used in a 'C' command, as in: =LIX;CA@,LXI;W would search for the string LIX, change it to an LXI, and write it back. > Gets saved buffer. '<' and '>' may be used to move a sector to another place. >> Restore "oldest" unrestored sector saved by '<<' command. This command may be "buried" in the middle of an infinite repeat '/', because it will stop operating when there are no more sectors in the buffer. ? Gives command summary. A Dump sector, ASCII only. CHaddr,val,val,val... change hexadecimal in sector. CAaddr,char string... change ASCII in sector. '' may be hex imbedded in the ASCII: ca0,OK<1a> Note: use 'W' to write changes to disk. The 'C' "echoes" overlaid data for verification. CHaddr-addr,byte or, CAaddr-addr,byte Repeats a change. D Dump sector, hexadecimal and ASCII. Fname print directory for file "name", then positions to it's directory sector. F Find next occurrence of name in the directory. Gnn Position to group nn and read. G Shows current position. H Dump sector, hexadecimal only. L Re-logs in the current disk. You may pull out a disk, put in a new, and "L" just to log it in. (See "LOGGING IN DISK" in NOTES below) Lx Logs in disk 'x', such as: LB M Dumps a map of the group allocations for files. or, Mn Shows which file is allocated to group "n". 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). P Toggle printer switch on/off. Q Quiet: Preceeding any command, suppresses console output. R Reads the sector currently positioned to into memory. Note: 'R' (Read) is implicit in the 'G', '+', and '-' commands, but NOT in the 'S' and 'T' commands. Snn Position to sector nn, and read. Tnn Seek to track nn (no read). Ux Logs user 'x' for next F command. Displays the character '?' error if not CP/M-80 version 2.0 (or greater). V Views the current sector (assumes ASCII data). Vnn Views nn sectors. W Write back the current sector. Note: may not be used after an F command, as CP/M was used to find the file in the directory. X Exit back to CP/M (Must press return). Z Sleep - causes the program to pause, such as to look at a dump. 'Z' is 1 second. Znn is nn tenths of a second on a 2 MHz 8080 CPU. 3.0 Usage Notes 3.1 Multiple Commands: May be separated by ";" Example: the following commands will erase the B: disk directory to all E5's: lb "Log-in" (select) the 'B:' drive. g0 Position to the start of the directory. ch0-7f,e5 Fill with the value 'E5' hexadecimal. < Save the sector >;w;+;/16 Restore, write, next repeat 16 times. This could be shortened to: lb;g0;ch0-7f,e5;< >;w;+;/16 3.2 Dump Commands - 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 3.3 Logging in Disk - Some problems may arise when "logging-in" diskettes with "mixed-density" (i.e., Track 00 is single density, and the directory tracks are double density, ala IBM System 34 type disks). A solution is to log in a disk which is OK, and is of the same density as the disk that you want to examine and alter, then put in the new disk WITHOUT logging it in. However, you are now opening yourself up to possible problems because of the buffering of physical sectors in the BIOS. The best technique, (but not guaranteed), would be to seek to the unused inner tracks of the first disk, do the read, THEN change disks. That way if it writes anything, you won't have destroyed anything...assuming the disk is not completely full. Another technique, assuming the second disk does not contain a CP/M system, would be to seek to Track 1, then do the read there, and then change disks to the new one. 3.4 Sector Buffers (The '<<' and '>>' commands) - Up to 255 sectors (only because its a 1 byte counter) may be saved by '<<'. ANY TIME '<' is executed, the buffers are "thrown away". One '>>' to fetch a saved buffer and make it available for writing, may be issued for each previous '<<'. The 'M' (directory map) command uses an area of memory for a buffer. To minimize problems (caveat programmer), the MAP buffer is placed a the END of the CURRENTLY HIGHEST USED '<<' buffer. On small systems, where many buffers have been saved via '<<', the 'M' command might report that it ran out of memory. Executing '<' or '>>' a sufficient number of times for it to tell you there are no more sectors in the buffer, will then make room available in memory at a lower address. Then 'M' may be used for "mapping" the directory. 4.0 Interpreting CP/M Directory Data 4.1 Single Density 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' (find 'SID.COM') command: 40 00534944 20202020 20434F4D 0000003A *.SID COM...:* 50 33343536 3738393A 00000000 00000000 *3456789:........* First line - 40 00534944 20202020 20434F4D 0000003A *.SID COM...:* || ||| | || || | | || ||^----HEX File Name-----^ || || ^File Name^ || || || || in ASCII || || Extent-^^ || || || || || || File Size in Sectors-^^ || || || ^^-00 = File Active (other values (e.g., 03 = User Number 3) || E5 = File Erased ^^-Displacement of the "line" (16 entries/line) in the directory sector Note: for the newcomer to "CP/M jargon", a file 'extent' (actually the extension of a file) indicates to the CP/M BDOS the number of 16 thousand (16K) consecutive bytes contained within a file. Extents are numbered from 0 to 31. One extent may contain 1, 2, 4, 4, 8 or 16 blocks (a block, is a basic unit of disk space allocation, and may be 1K, 2K, 4K, 8K or 16K consecutive bytes). These blocks then are assigned group numbers (a "group" is a group of disk sectors), and are allocated dynamically to accomodate the required disk space on a disk, as used by a given file (Group 0 is ALWAYS the start of the directory group). Therefore, a file "name" might appear in the director a number of times , depending on the number of extensions required to accomodate the files size (refer to the sample disk "MAP" in section 2.0 Usage...the file PBIOS.ASM shows multiple extents)...Whew! With that out of the way then, I hope this makes sense: Second line - 50 33343536 3738393A 00000000 00000000 *3456789:........* | | | | | ^- The allocation groups ^-----Allocation Group Numbers-----^ that just happened to be printable! 4.2 Double Density The following is a sample of SID.COM running on a double density system: :fSID.COM <-- Find 'SID.COM' on the disk... 00 00534944 20202020 20434F4D 0000003A *.SID COM...:* 10 38003900 3A003B00 00000000 00000000 *8.9.:.;.........* G=0000:00, T=2, S=1, PS=0 The primary difference is that the groups now occupy 2 bytes, i.e. "38 00", "39 00", etc. This follows the INTEL and CP/M convention of putting 16 bit values high-byte-first. Thus it means group 0038, 0039, etc. Note that in double density, each group stood for 2K, not 1K, so there were half as many groups for the same file. Be VERY careful when patching a directory under double density. I once made the mistake of putting, for example: ch10,38,39,3a,3b... When I went to read this file, it tried to access group 3938, with resultant angry exclamations from the disk stepper as it attempted to go south to Peoria for the data. 5.0 DU Usage Examples 5.1 Erased Program Recovery Let's suppose that you have just put on the "final touches" to your latest'n'greates program to market as your new "let's get poor quick" scheme...you (of course) have NEVER made a back-up copy after having put in 10^16 (that 10 to the 16th power!) weekends of time into it. So you proudly examine the directory of your pride-and-joy: A0>dir b: B: BIZ-INIT BAS : BIZ-CALC BAS : BIZ-CHRT BAS : BIZ-WIZ TXT B: BIZ-WIZ BAS Yep...All there, and...(ring, ring...its the #%&"*+ phone again!). O.K. be back in a few minutes and get a printer listing for posterity...(tick, tick...minutes turn to hours...): Ah yes, lets see where was I? Oh yes, that guy called an wanted to modem over his latest version of FOOBAR...Fine, better make some room on this "scratch disk" in the B: drive...so we: A>era b:*.* <-- lets just get rid of whatever junk is there... ALL (Y/N)?y <-- sure, if I can't remember whats there, can't be important! A0>dir b: <-- and just to be sure... NO FILE <-- Yep! No files left...but...AAaarrgghh! The wrong $&+#* disk!!! What do you do,... what do you do??? Do you...D You....Dee U.....ahh Hah! DU!!! Disk Utility to the rescue! I just KNEW something clever would (eventually) emerge from my beer-fogged brain to save my ASCII (err, ahh)...so here I go! A0>du DISK UTILITY ver 7.7 Universal Version Type ? for help Type X to exit :lb <-- "log" disk B: (forest reclamation project!) :g0;d <-- Go to Group 0 (always the directory group) and Dump: G=00:00, T=2, S=1, PS=1 00 E542495A 2D494E49 54424153 0000001C *eBIZ-INITBAS....* 10 02030405 00000000 00000000 00000000 *................* 20 E542495A 2D43414C 43424153 00000050 *eBIZ-CALCBAS...P* 30 06070809 0A0B0C0D 0E0F0000 00000000 *................* 40 E542495A 2D434852 54424153 00000019 *eBIZ-CHRTBAS....* 50 10111213 00000000 00000000 00000000 *................* 60 E542495A 2D57495A 20545854 00000029 *eBIZ-WIZ TXT...)* 70 14151617 18190000 00000000 00000000 *................* Hmmm...my files alright with funny little "e's" in front of'em...lets also look at the next directory sector: :+;d <-- advance +1 sector and Dump it also: G=00:01, T=2, S=2, PS=7 00 E542495A 2D57495A 20424153 00000080 *eBIZ-WIZ BAS....* 10 1A1B1C1D 1E1F2021 22232425 26272829 *...... !"#$%&'()* 20 E542495A 2D57495A 20424153 0100006B *eBIZ-WIZ BAS...k* 30 2A2B2C2D 2E2F3031 32333435 36370000 **+,-./01234567..* 40 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 50 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 60 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 70 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* Well, its all sitting there (sort'a!) in the directory...lets backup one sector, and start fixing things up to recover those erased files: :- <-- minus 1 sector... G=00:00, T=2, S=1, PS=1 :ch0,0;ch20,0;ch40,0;ch60,0 <-- CHange all "E5's" to zeros: E5E5E5E5 <-- the "E5's" (erased file flags) evaporate before our very eyes! :d <-- Dump it just to check... 00 0042495A 2D494E49 54424153 0000001C *.BIZ-INITBAS....* 10 02030405 00000000 00000000 00000000 *................* 20 0042495A 2D43414C 43424153 00000050 *.BIZ-CALCBAS...P* 30 06070809 0A0B0C0D 0E0F0000 00000000 *................* 40 0042495A 2D434852 54424153 00000019 *.BIZ-CHRTBAS....* 50 10111213 00000000 00000000 00000000 *................* 60 0042495A 2D57495A 20545854 00000029 *.BIZ-WIZ TXT...)* 70 14151617 18190000 00000000 00000000 *................* :w <--Write this directory sector back to the disk: :+ <-- advance to the next directory sector: G=00:01, T=2, S=2, PS=7 :d <-- Dump it also, to be sure... 00 E542495A 2D57495A 20424153 00000080 *eBIZ-WIZ BAS....* 10 1A1B1C1D 1E1F2021 22232425 26272829 *...... !"#$%&'()* 20 E542495A 2D57495A 20424153 0100006B *eBIZ-WIZ BAS...k* 30 2A2B2C2D 2E2F3031 32333435 36370000 **+,-./01234567..* 40 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 50 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 60 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 70 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* :ch0,0;ch20,0 <-- just CHange for the two directory entries... E5E5 :d <-- why "valley girls" take 2 birth control pills (to be sure, fer'sure!) 00 0042495A 2D57495A 20424153 00000080 *.BIZ-WIZ BAS....* 10 1A1B1C1D 1E1F2021 22232425 26272829 *...... !"#$%&'()* 20 0042495A 2D57495A 20424153 0100006B *.BIZ-WIZ BAS...k* 30 2A2B2C2D 2E2F3031 32333435 36370000 **+,-./01234567..* 40 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 50 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 60 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* 70 E5E5E5E5 E5E5E5E5 E5E5E5E5 E5E5E5E5 *eeeeeeeeeeeeeeee* :w <-- Write this directory sector as well, before we quit! :x <-- eXit to CP/M-80... A0>dir b: <-- and as if by magic... B: BIZ-INIT BAS : BIZ-CALC BAS : BIZ-CHRT BAS : BIZ-WIZ TXT B: BIZ-WIZ BAS A0>...It's all done with mirrors! 5.2 Modifying a disk for "Program Autoload" By modifying a portion of the CP/M operating system, you can force it load automatically and execute a command file. This can be particularly useful if you want to set-up some fancy printer initialization, modify some serial port Baud rate or data format parameters, etc. To enter an "autoload" filename to a CP/M diskette: :t2;s1;d <-- position to Track 2, Sector 1, and Dump... T=2, S=1, PS=0 (NOTE: this is representative of my disk only!) T=2, S=1, PS=0 00 C35CDDC3 58DD7F00 20202020 20202020 *C\]CX].. * 10 20202020 20202020 434F5059 52494748 * COPYRIGH* 20 54202843 29203139 37392C20 44494749 *T (C) 1979, DIGI* 30 54414C20 52455345 41524348 20200000 *TAL RESEARCH ..* 40 00000000 00000000 00000000 00000000 *................* 50 00000000 00000000 00000000 00000000 *................* 60 00000000 00000000 00000000 00000000 *................* 70 00000000 00000000 00000000 00000000 *................* :ca8,SIGNON<0> <-- Change ASCII, address 8 to 'SIGNON' and '0'. :ch7,6 <-- Change Hex, address 7 to a value of 6 (length byte) 00 <-- what the value "was" prior to the change :d <-- Dump the disk sector for display 00 C35CDDC3 58DD7F06 5349474E 4F4E0020 *C\]CX]..SIGNON. * 10 20202020 20202020 434F5059 52494748 * COPYRIGH* 20 54202843 29203139 37392C20 44494749 *T (C) 1979, DIGI* 30 54414C20 52455345 41524348 20200000 *TAL RESEARCH ..* 40 00000000 00000000 00000000 00000000 *................* 50 00000000 00000000 00000000 00000000 *................* 60 00000000 00000000 00000000 00000000 *................* 70 00000000 00000000 00000000 00000000 *................* :w <-- Write the disk sector. :x <-- eXit to CP/M. You could now "cold boot" this CP/M-80 system disk, and it would "autoload" by running the 'SIGNON' program (whatever that is!) prior to doing anything else. 5.3 Finding and Modifying Program Data Quickly This example show how to find a filename in the directory, then locate the data within the file for subsequent modification (in this case just to change a version number in the source code...we could (I suppose) have used (barf...) 'ED'!): :fSYSTOSYS.ASM <-- Find the program 'SYSTOSYS.ASM' 20 00535953 544F5359 5341534D 00000080 *.SYSTOSYSASM....* 30 0E010F01 10011401 15011601 4F015001 *............O.P.* G=0000:00, T=4, S=1, PS=0 :g10e <-- Go to Group '10E' (see it above at address 30 and 31? Also, G=010E:00, T=71, S=33, PS=32 remember to enter 2K groups "bas-akwards" from what you see. In this case NOT E01!) :d <-- Dump it... 00 3B202020 20202020 20202020 20202020 *; * 10 436F6D70 7570726F 20382F31 3620436F *Compupro 8/16 Co* 20 6D706174 69626C65 20535953 544F5359 *mpatible SYSTOSY* 30 53205665 7273696F 6E20312E 340D0A3B *S Version 1.4..;* 40 20202020 20202020 20202020 20202043 * C* 50 6F707972 69676874 20284329 20313938 *opyright (C) 198* 60 312C2031 3938322C 20313938 33206279 *1, 1982, 1983 by* 70 204B656C 6C792053 6D697468 0D0A3B0D * Kelly Smith..;.* :ca3c,5 <-- I want to change from version 1.4 to 1.5: 4 :d <-- what sound does the Lone Rangers horse make? (Dump'ta'da'Dump'ta'da...) 00 3B202020 20202020 20202020 20202020 *; * 10 436F6D70 7570726F 20382F31 3620436F *Compupro 8/16 Co* 20 6D706174 69626C65 20535953 544F5359 *mpatible SYSTOSY* 30 53205665 7273696F 6E20312E 350D0A3B *S Version 1.5..;* 40 20202020 20202020 20202020 20202043 * C* 50 6F707972 69676874 20284329 20313938 *opyright (C) 198* 60 312C2031 3938322C 20313938 33206279 *1, 1982, 1983 by* 70 204B656C 6C792053 6D697468 0D0A3B0D * Kelly Smith..;.* :w <-- Write it... :x <-- Do with me what you will (just don't leave me unsatisfied!) A>Ahhhhh...thats better! 5.4 A "Poor Man's" Disk Test DU can also function in the capacity of a "Poor Man's" disk test by performing simple sequential write/read/seek functions with user specified data patterns. Here in very simple form, is a 4 sector non-destructive read-only/seek test. Any susbsequent errors would be trapped by the CP/M BDOS and stop the "test" with whatever error message was appropriate (e.g., BDOS Err on B: BAD SECTOR): :t20;s1 G=0040:00, T=20, S=1, PS=0 :+;+;+;+;-;-;-;-;/ <-- read forward 4 sector, G=0040:01, T=20, S=2, PS=1 read backward 4 sectors, G=0040:02, T=20, S=3, PS=2 repeat 'ad nauseum' (actually until ^C) G=0040:03, T=20, S=4, PS=3 G=0040:04, T=20, S=5, PS=4 G=0040:03, T=20, S=4, PS=3 G=0040:02, T=20, S=3, PS=2 G=0040:01, T=20, S=2, PS=1 G=0040:00, T=20, S=1, PS=0 G=0040:01, T=20, S=2, PS=1 G=0040:02, T=20, S=3, PS=2 G=0040:03, T=20, S=4, PS=3 G=0040:04, T=20, S=5, PS=4 G=0040:03, T=20, S=4, PS=3 ~ ~ | days or weeks later... | ~ ~ G=0040:03, T=20, S=4, PS=3 G=0040:02, T=20, S=3, PS=2 G=0040:01, T=20, S=2, PS=1 G=0040:00, T=20, S=1, PS=0 G=0040:01, <-- interrupted with ^C from the keyboard. : By using your imagination, you can come-up with a variety of usefull applications for DU...Have fun!  G=0040:02, T=20