LDOS 5.3.1 for the Model III - BACKUP/CMD Disassembled

BACKUP/CMD

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LDOS 5.3.1 BACKUP/CMD Disassembly - The Disk Backup Utility (Model III)

BACKUP copies a diskette: BACKUP [-][partspec]:s :d (parameters). The file holds three programs. The front end (5A00H, the transfer address) reads the command line and the parameters, mounts both diskettes, checks the source's master password and decides how to copy. Two engines are loaded elsewhere and moved to 5A00H, over the front end, by the engine selector (6C00H): the mirror image engine (5E00H, run at 5A00H-5E08H) copies cylinder by cylinder; the file by file engine (6300H, run at 5A00H-6147H) copies through the file system. The code both engines share lies below 5A00H (5285H-5486H): the endings, the prompts for the diskettes and the calls of the drive's driver.

The file is a load module of 5880 bytes: a copyright record, 27 load blocks with 5717 bytes in six parts (5200H-521CH, 5285H-55F7H, 5A00H-5D51H, 5E00H-6208H, 6300H-6A47H, 6C00H-7021H), and the transfer address 5A00H. The memory between the parts is used for buffers and is shown as DEFS rows.

Which Engine

The Engines

About This Page

5200H - The Selection Cells and the Parameter Cells

The first load block holds 29 bytes of data: the cells the front end fills from the partspec and the DATE parameter, the date conversion flag, and five of the cells @PARAM writes (NEW, OLD, MOD, QUERY, SYS; the cells of MPW, INV, X and DATE are operands of instructions elsewhere). The file by file engine (6300H, run at 5A00H) reads them to choose the files.

5285H - The Work Area Pointer and the Endings

The second load block starts with the pointer to the work area, then the code both engines share: it lies below 5A00H, so the move of an engine to 5A00H leaves it in place. 5287H ends a backup that is complete, 529BH-52AAH one with an error, 52ACH-52BDH one that is given up; all of them first put the clock back and clear the work area (52C0H).

52C0H - Put the Clock Back, Ask for the System Diskette, Clear the Work Area

Called by all three endings. The mirror image engine stores the byte of 4012H it replaces at 52C1H (5ED6H); it is put back here with interrupts on. After an X backup, or a backup with source and destination on one drive, the system diskette is asked for in drive 0 (52FBH). Then the memory from the work area pointer (5285H) up to HIGH$ is filled with 00H, unless the pointer is still 0000H.

52F6H - Ask for the System Diskette

Called at the end by 52DCH; 52D3H enters at 52FBH, past the test of 5302H. The drive state 20H (drive 0, bit 5) goes to the prompt routine with Insert SYSTEM disk <ENTER>; @CKDRV must then accept the diskette in drive 0, or the drive state is put back and the prompt comes again.

531AH - Ask for the Source Diskette

5327H is the call of the engines: when the source diskette is not the one in the drive (bit 7 of 53D5H clear), it is asked for (531AH), and on one drive its pack identity is then checked: the 10 bytes at 00CEH-00D7H of its allocation table (the master password hash and the diskette name) must equal those of the source diskette read at the start (57CEH). A diskette whose boot sector does not start with 00H, or another pack identity, is asked for again.

5387H - Ask for the Destination Diskette

5394H is the call of the engines: when the destination diskette is not the one in the drive (bit 6 of 53D5H clear), it is asked for (5387H), and on one drive its boot sector must start with 76H, the byte the mirror image engine writes there (5E75H). The file by file engine stores C9H at 53BDH (6311H (run 5A11H)), so for it any diskette that can be read is taken.

53CEH - The Prompt Routine

53D4H takes the wanted drive state in Register A (bits 2-0 the drive, bit 7 the source, bit 6 the destination, bit 5 the system diskette). When it is the state at 53D5H, or the source and destination are two drives (53DCH not 00H), the drive is only selected (5439H). Else the state is stored and the prompt at Register Pair HL flashes (shown, cleared, shown) until ENTER; BREAK gives up the backup. 53CEH (the front end) and 53E0H (the file by file engine) ask whatever the state.

544CH - Clear the Keyboard Request Bits

Clears bits 0-2 of KFLAG$ (BREAK, SHIFT @, ENTER), which the keyboard scan 4DBEH only sets.

5455H - The Disk Functions

Eight entries, each loading a function of the drive's driver into Register A, then the common part 5472H: Register B = the function, Register C = the drive number from the drive state at 53D5H (also stored at LDRV$, 4427H), Register A = 20H with the NZ FLAG, and a call through the drive code table at Index Register IY. A drive that is not present (its table starts with C9H, a RET) returns at once with Register A = 20H and the NZ FLAG: error 20H. Callers must have Index Register IY at the drive's table (5439H, 543FH).

5487H - The Texts of Both Engines

Texts below 5A00H, so they stay in place when an engine is moved there. 0AH starts a new line, 0DH ends a text and its line, 03H ends a text and leaves the cursor where it is; 1DH puts the cursor at the start of its line and 1EH clears to the end of the line, so the prompts are written over one line again and again (53FEH).

55F8H - The Buffers Below 5A00H

Memory not in the file, used by the front end and both engines: the bytes kept from the source's boot sector, the two allocation tables and a sector buffer. In the file by file engine 5800H holds the directory sector of the source being scanned.

5A00H - The Front End: the Partspec and the Drives

The transfer address. LDOS runs BACKUP with Register Pair HL at the command line after the command's name. The stack goes to 41E5H, the banner is shown, and the line is read: a minus sign (all files but those named), the file name and the extension of the partspec into 5205H-520FH, then :d, the source drive, and :d, the destination drive. A drive that is not given is asked for (one character), and then the rest of the line is not read: the reply buffer takes the place of the command line.

5A7FH - The Parameters, One Drive, the DATE Parameter

@PARAM reads the parameters with the table at 6D74H (MPW, SYS, INV, MOD, QUERY, X, DATE, NEW, OLD and their short forms). Source and destination on one drive are refused during a JCL job. A DATE text (the address of its first character is in the cell 5AA2H) gives the first date at 5201H and the second at 5203H, with the mode at 5200H: 80H M/D/Y-, 01H -M/D/Y, 81H M/D/Y or M1/D1/Y1-M2/D2/Y2 (a single date is stored as both). Then the attribute byte at 5210H from SYS and INV.

5AF9H - Backup by Class, the Date, the Source Diskette

Any partspec or any of SYS, INV, MOD, DATE, NEW, OLD, QUERY gives a backup by class: an OR of their first bytes (the extension's and file name's first character less 20H) goes to 6C01H, the operand of LD A at the engine selector, and Backup by class invoked is shown. X and MPW do not count. The date of the system goes to 527DH as text; SYS2/SYS is loaded; then the source diskette is asked for when needed and its drive must answer (6CBFH).

5B73H - The Source Diskette's Boot Sector and Allocation Table

The source drive is size tested (bit 5 of +03H, 8 inch, kept at 5C14H), its boot sector is read: bytes 09H-0AH (the operand of the boot sector's LD IY) and 16H-25H go to 55F8H-5609H for the mirror image engine, byte 02H, the directory cylinder, goes to the drive's table. The allocation table is read into 5700H, the master password is checked, the drive's table is set from the allocation table again, and the date conversion count (5212H) gets FFH when the source's date flag bit is clear.

5C0EH - Mirror Image or Reconstruct

A mirror image copy needs the same drive size (bit 5 of +03H), a destination that can be verified at cylinder 0 sector 0 (else Destination disk not formatted - Backup aborted), and the same bits 6-4 of the configuration byte (+CDH) in both allocation tables: double density, two sides, cylinder 0 in single density. The destination's allocation table goes to 5800H. With different cylinder counts (+CCH) the operator is asked; a backup by class always takes the file by file engine. A backup reconstruct is the file by file engine without a selection.

5C72H - Ask About the Cylinder Count

Called by 5C63H when the two allocation tables give different cylinder counts. A reply starting with Y or y gives the Z FLAG.

5C89H - The Master Password

The source diskette's master password hash (+CEH-+CFH of its allocation table, 57CEH) is checked. 42E0H, the hash of PASSWORD, needs nothing. Otherwise MPW's text, or the reply to Master password ?, is hashed by SYS2/SYS (request E4H through 6C68H); the hash 113DH (the password RS0LT0FF) or the diskette's own hash lets the backup go on, any other gives Invalid master password and the end.

5CB1H - Copy a Name of the Partspec

Takes the character in Register A and the ones at Register Pair HL into the field at Register Pair DE, at most Register B characters: 24H ($), digits 30H-39H and every character from 41H up (61H and up folded by clearing bit 5). Any other character ends the field; Register A returns with it, and after Register B characters with the next character of the line.

5CCCH - Read a Date of the DATE Parameter

Reads MM/DD/YY at Register Pair HL (two digits in each field) into 525FH (month), 525EH (day) and 525DH (year), checks the month (1-12) and the day against the table of days at 7006H, and returns Register Pair BC packed so that dates compare as numbers: Register B bits 7-3 the year less 1980, bits 2-0 bits 3-1 of the month; Register C bit 7 bit 0 of the month, bits 6-2 the day. Any error gives Bad date format and the end.

5D20H - Read the Fields of a Date

Reads three numbers of two digits at Register Pair HL, separated by the character in Register C, into 525FH, 525EH and 525DH, the first at the top. The Z FLAG when all three are read; the NZ FLAG for a field without two digits or another separator.

5D35H - Read Two Digits

Two decimal digits at Register Pair HL give their value in Register A and Register E, with the Z FLAG. A character that is not a digit gives the NZ FLAG.

5D52H - Memory Above the Front End

Not in the file.

5E00H - The Mirror Image Engine (Run at 5A00H): Pack Identities and Lock Outs

5E00H-6208H is loaded here and moved to 5A00H-5E08H by the engine selector (6C06H) before it runs: every address it uses in 5A00H-5E08H is 0400H below the row that holds it on this page, and its JP and CALL operands are run addresses. It copies the source diskette cylinder by cylinder. First the pack identities (+CEH-+D7H of the two allocation tables, 57CEH and 58CEH) are compared, then every cylinder is checked: a granule the source uses must not be locked out on the destination.

5E4AH - Mark the Destination (Run 5A4AH)

The destination's boot sector is read. When its cylinder 0 is in single density with the rest in double density (bit 7 of +04H, from bit 4 of the configuration byte, 6D34H), the bytes the front end kept from the source's boot sector go into it: 09H-0AH (the operand of LD IY,0000H) and 16H-25H. Its first byte becomes 76H and it is written back: 53BBH finds the destination by this byte, and 60B2H stores 00H there again at the end. The copy never reads or writes sectors 0 and 1 of cylinder 0.

5E7DH - The Geometry and the Room in Memory (Run 5A7DH)

From the source's drive table: the directory cylinder (to 5FA6H), the sectors on a cylinder (to five CP operands), the sectors of a cylinder 0 in single density, 10 or 20 (to three CP operands), and the cylinders the work area holds, one 256 byte page per sector (to 5F4CH). Then interrupts are turned off and the RET goes to 4012H.

5EE7H - The Read Pass (Run 5AE7H)

From cylinder Register D on, each cylinder is looked at in the two allocation tables: its granules that hold data on the source (in use and not locked out) OR the destination's locked out granules become the destination's allocation byte (58xxH). A cylinder without data is passed over. The others are read, sector by sector, one 256 byte page each, into the work area, until it is full (5F4CH) or cylinder 95 is passed. Sectors 0 and 1 of cylinder 0 (the boot sectors) are never read; a directory sector (result 06H) is read like any other.

5F5EH - The Write Pass (Run 5B5EH)

The same cylinders, from the first of the group (5F68H), are written to the destination from the work area: a cylinder without data is passed over again, the boot sectors are not written, the sectors of the source's directory cylinder are written with the deleted data mark (error 12H if that fails), the others with the normal mark.

5FDCH - The Verify Pass (Run 5BDCH)

The group is read back from the destination without the bytes being stored (function 0AH): a sector with the deleted data mark (06H) is good. Then the read pass goes on with the next cylinder (603CH).

603FH - Finish the Mirror Image (Run 5C3FH)

The destination's allocation table (5800H) gets +CEH-+FFH of the source's (the pack identity, the date, the AUTO command) and the date of today (527DH), and is written to sector 0 of the directory cylinder and verified. In every directory record of the destination (sectors 2 to the last of the directory cylinder) the bit of a changed file (+01H bit 6) is cleared, but in extension records (+00H bit 7). Both boot sectors get the directory cylinder. When the destination's own directory cylinder was elsewhere and no data lands on it, its sectors are filled with E5H. Then the bits are cleared on the source too; a write protected source gives a message and the backup is complete anyway.

6148H - Write a Number of Three Characters (Run 5D48H)

Register A (0-255) is written at Register Pair HL as hundreds, tens and units: a 0 in the hundreds or tens place is left a space, the units always get a digit. The progress lines show the cylinder with it.

616EH - Not a Mirror Image (Run 5D6EH)

Reached from 5E43H when a granule with data on the source is locked out on the destination.

6174H - The Texts of the Mirror Image Engine

They move to 5D74H-5E08H with the engine, so its code uses addresses 0400H lower than the rows here.

6209H - Memory Above the Mirror Image Engine

Not in the file.

6300H - The File by File Engine (Run at 5A00H): Setup

6300H-6A47H is loaded here and moved to 5A00H-6147H by the engine selector (6C52H): every address it uses in 5A00H-6147H is 0900H below the row that holds it on this page, and its JP and CALL operands are run addresses. Its work area starts at 6300H. It copies file by file, through the file system, every file the selection lets through (a backup by class) or every file (a backup reconstruct). Setup: the last page of the work area into three operands, 53BDH made a RET (any destination diskette is taken), the destination's room for data (its sectors less those of two cylinders), its directory cylinder from its boot sector; with SYS, the destination is prepared as a system diskette.

63EAH - The Directory Scan (Run 5AEAH)

The source's hash index table (6200H) is walked in the order of its entries (record n is entry n: the sector of directory records is n AND 1FH plus 2, its place in the sector n AND E0H). A free entry (00H) and records 00H and 01H (BOOT/SYS, DIR/SYS) are passed over. Each record is read into 5800H and tested: in use (+00H bit 4), not an extension record (bit 7), changed (+01H bit 6) when MOD is given, a system file (bit 6) only with SYS, an invisible file (bit 3) only with INV, the partspec, the DATE range. 5AEAH and 5AEBH are where a file is passed over; BREAK ends the backup there; after the last entry the backup is complete.

64C1H - NEW, OLD and the Question (Run 5BC1H)

The file's name goes into the source control block at 521DH as NAME/EXT. With NEW or OLD the destination is asked for the file (@OPEN): NEW copies only files it lacks (error 18H), OLD only files it has, and both together any file whose @OPEN gives 18H or no error. With QUERY the question Backup NAME/EXT + {DD-Mmm-YY} ? is asked (the + for a changed file): Y copies, C copies this file and asks no more, anything else passes it over. Without QUERY, Copying file: and the name are shown and written to the job log.

6607H - A System File (Run 5D07H)

The specifications NAME/EXT.RS0LT0FF:d of the source (521DH) and of the destination (523DH) are made. A file whose record is 00H-07H or 20H-27H (Register B AND D8H is 00H) and has the attribute of a system file (bit 6) gets its record on the destination at the same place: a free record there is made a system file's record (5FH, 00H in +01H-+04H, FFH in +10H-+1FH), and the name, extension and password hash (+05H-+11H) are copied; a record of the destination that is not a system file's gives Can't create SYSTEM disk. For SYS0/SYS (record 02H) sectors 2-4 of cylinder 0 are copied as well, with C9H in byte 01H of the system information sector. Then the file is copied as any other.

66E2H - Copy a File (Run 5DE2H)

The source file is opened (@OPEN, records of 256 bytes, buffer at the work area); a file of more records than the destination's room for data (5DF4H) is passed over with a message. The destination file is opened or created (@INIT) and its whole length written at once by 5FA8H (writing its last record), so a full diskette shows before any data moves: the file is killed, and a new destination diskette is asked for (not during a JCL job). Then the records are read into the work area page by page and written to the destination with @VER until the end of the file; the end of file byte and the record length go across, and the file is closed.

677FH - The Directory Records Afterwards (Run 5E7FH)

The destination file's directory record gets +00H-+04H (with the bit of a changed file cleared) and +10H-+13H of the source's record: attributes, date, end of file byte, record length, password, time and year. With the date conversion count at 00H (an old dated source to a new dated destination) the year (+02H bits 2-0) goes to +13H and +12H is cleared. Then the bit is cleared in the source's record too, unless the source turned out write protected (the message is given once).

6819H - Make the Two File Specifications (Run 5F19H)

Register Pair DE is at the end of NAME/EXT in 521DH. .RS0LT0FF: and the source drive's digit and 03H go after it; the whole block is copied to 523DH and the digit after the colon there becomes the destination drive's.

684AH - Pack a Record's Date (Run 5F4AH)

Register Pair HL at +01H of a directory record. Register Pair DE gets the date packed as 5CCCH packs the DATE parameter: Register D bits 7-3 the year less 1980, bits 2-0 bits 3-1 of the month; Register E bit 7 bit 0 of the month, bits 6-2 the day. The year comes from +13H bits 4-0 when bit 0 of 475DH is set (the date flag of drive 0, whatever drive the record is from), else from +02H bits 2-0.

6874H - Write the Allocation Table (Run 5F74H)

Writes the allocation table at Register Pair HL's page (Register L set to 00H) to cylinder Register D sector Register E with the deleted data mark and verifies it: error 15H or 14H.

6889H - Write the Pages Read (Run 5F89H)

At the end of a file: the records read into the work area, from its first page up to the page below Register H, are written to the destination with @VER.

68A8H - Take the Space of the Whole File (Run 5FA8H)

Register Pair BC = the records of the file. Its last record (Register Pair BC less 1) is written with E5H bytes, so the file gets all its space at once: the Z FLAG when it fits. When the destination is full (error 1BH) the file is killed; during a JCL job the backup ends, else a new destination diskette is asked for (the prompt flashes until ENTER) and the NZ FLAG is returned.

68DFH - The Source and the Destination File (Run 5FDFH, 5FE8H)

5FDFH has the source diskette in its drive and Register Pair DE at the source's control block (521DH); 5FE8H the destination's (523DH). Register Pair BC is kept.

68F1H - Read the Hash Index Table (Run 5FF1H)

Reads sector 1 of the directory cylinder of the drive at Index Register IY into 6200H: Register A = 16H and the Z FLAG when it has the deleted data mark.

6907H - The Texts and Tables of the File by File Engine

They move to 6007H-6147H with the engine, so its code uses addresses 0900H lower than the rows here.

6C00H - The Engine Selector

Entered from 5C60H and 5C66H, and at 6C13H from 5C6FH. With no selection (6C01H 00H) the mirror image engine (5E00H, 0500H bytes) is moved to 5A00H, over the front end. Otherwise the file by file engine (6300H, 0900H bytes) is moved there, but not for source and destination on one drive; with X the system files 2, 3, 8 and 10 must be kept in memory by SYSRES. The work area starts at the page boundary above the moved bytes (5F00H or 6300H); then the engine runs at 5A00H.

6C68H - The Requests to SYS2/SYS

6C68H takes 8 characters (6C71H) and falls into request E4H: SYS2/SYS hashes the 8 bytes at Register Pair DE into Register Pair HL. 6C6EH is request 84H, which only loads SYS2/SYS. The supervisor dispatcher drops the return address of the RST 28H, so each request returns to the caller of 6C68H, 6C6BH or 6C6EH.

6C71H - Take Eight Characters

Register Pair DE not 0000H: up to 8 characters of the text at Register Pair DE (a parameter's text, ended by 0DH, a comma or a quote). Register Pair DE 0000H: the question at Register Pair HL is displayed and up to 8 characters are typed (BREAK gives up the backup). The 8 places at 5900H are filled with spaces after the text and lower case letters made upper case; Register Pair DE returns at 5900H.

6CBFH - Test a Drive and Set Its Table from the Diskette

Called with Index Register IY at the drive's table and the drive state at 53D5H. A drive whose table starts with C9H returns at once (NZ, Register A = 06H). The head is put on a known cylinder (a Restore when +05H is above the highest cylinder), the drive selected; unless +04H bit 4 is set the diskette must turn: the index hole off, on, off within 15 ticks of TIMER$, half a second at the 30 ticks a second of the Model III (6D4FH). The allocation table is read into 4300H, and from its +CCH-+CDH: the bit of the drive in 475DH (the date format, configuration bit 3), +06H (35 + the cylinders less 35, less 1), +04H bit 7 (cylinder 0 in single density, bit 4) and +04H bit 5 (two sides, bit 5). Returns the Z FLAG, with the CARRY FLAG for a write protected diskette (the status or +03H bit 7); a failure gives the NZ FLAG with Register A = 08H.

6D4FH - Look at the Index Hole

Returns the NZ FLAG while the index hole is at the head (status bit 1 after a Type I command). When TIMER$ (4288H) reaches the deadline in Register D, the caller's return address is dropped and 6CBFH returns with error 08H.

6D61H - Is the Date Format Bit Set?

Register A = the drive state (bits 2-0 the drive). BIT n,A with n the drive is made at 6D72H and run on 475DH: the NZ FLAG when the drive's diskette has the date format of this release.

6D74H - The Parameter Table and the Texts of the Front End

The table of @PARAM (5A7FH): 16 entries of a name of 6 characters (spaces after it) and the address of the parameter's cell, then 00H. Then the texts of the front end and the days of the months for the DATE parameter.