LDOS 5.3.1 for the Model III - CONV/CMD Disassembled

CONV/CMD

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LDOS 5.3.1 CONV/CMD Disassembly - Files from TRSDOS 1.3 (Model III)

CONV/CMD copies files from a Model III TRSDOS diskette onto an LDOS diskette; the manual (M-40-060) says two drives are needed and that TRSDOS 1.2 and 1.3 diskettes are to be copied with CONV, never repaired. The command is CONV [-][name][/ext]:s [:d] [(parameters)]: s the drive of the TRSDOS diskette (not drive 0), d the drive of the LDOS diskette. The parameters are VIS, INV and SYS (the classes of files; none given means all), NEW and OLD (only files that do not, or do, exist on the destination), QUERY (on unless QUERY=N: CONV asks before each file, and again before it replaces one), and DIR, which the manual does not name, to list the files that match and copy nothing; without :d CONV lists them too. A $ in the name or extension matches any character, and a name shorter than 8 characters matches every name that starts with it. A minus sign before the name, not named in the manual either, takes the files that do not match.

The file is a load module of 1491 bytes: a record of type 1FH with the text Copyright 1991 MISOSYS, Inc., All rights reserved, six load blocks for 5200H-5783H (1412 bytes) and the transfer address record for 5200H. CONV reads the TRSDOS diskette with SYS0/SYS's RDSECT (4777H) itself, sector by sector: it sets the highest sector in the drive code table of the source drive to 18 (TRSDOS 1.3 numbers its sectors 1-18) and puts the table back at the end. It reads the directory into 5800H-67FFH, follows the extents of each file, and writes the sectors through the file routines of LDOS (@OPEN, @INIT, @POSN, @WRITE, @REW, @CLOSE) with a buffer from 6800H to HIGH$ less 256.

What CONV Does

About This Page

Load Blocks in File Order

The six load blocks of the file, after the copyright record: 1412 bytes, 5200H-5783H. The transfer address is 5200H.

Sections of the Disassembly

Memory CONV/CMD Uses

The entry points of CONV/CMD, then the data of the file, the operands it changes, and the cells outside the file that it uses, by address.

Entry Points

Data in the File

Operands Changed While It Runs

Cells Outside the File That CONV/CMD Uses

5200H - Entry: the Banner and the File Specification

LDOS Ready loads CONV/CMD at 5200H-5783H and jumps to 5200H, the transfer address, with Register Pair HL at the rest of the command line after the word CONV and the spaces after it. The command is CONV [-][name][/ext]:s [:d] [(parameters)] (M-40-060): s the TRSDOS 1.3 diskette, d the LDOS diskette. The banner is displayed and the BREAK, SHIFT @ and ENTER flags of KFLAG$ are cleared. A minus sign before the file specification, which the manual does not name, turns the match round: the files that do not match are taken. The name and the extension are copied over the template 56F0H-56FAH, 11 characters of $, the character that matches any character: a name shorter than 8 characters keeps $ in the rest, so it matches every name that starts with it.

523AH - The Drives and the Parameters

The source drive must follow as :s (else error 2CH) and cannot be drive 0 (Source cannot be drive 0). The destination :d may be left out: then, or with the parameter DIR, CONV only lists the files that match (the drive cell 57C5H holds FFH). @PARAM reads the table at 560FH, which stores FFFFH, or the value given, into the operands of the LD instructions at 5256H-5277H; their bytes are collected into two cells: 52ECH (any of SYS, VIS, INV given) and 539CH (NEW or OLD given). QUERY is on unless QUERY=N is given.

528AH - Read the TRSDOS 1.3 Directory

The drive code table of the source drive is saved at 57CDH-57D6H (54F5H puts it back at the end) and its +07H, the highest sector of a track, is set to 12H: TRSDOS 1.3 numbers its 18 sectors 1-18. Sector 1 of cylinder 0 is the TRSDOS 1.3 boot sector: its byte 01H is the directory track, byte FEH the version of TRSDOS (13H for 1.3). The 16 sectors of directory records, sectors 3-18 of the directory track, are read into 5800H-67FFH. A read that returns error 06H counts as good: TRSDOS 1.3 writes its directory with the other data address mark.

52D4H - Choose the Files

For each record (Index Register IX and Register Pair HL at it, its first byte the attribute): BREAK ends CONV at @ABORT; a record not in use (bit 4 clear) or an extension record (bit 7 set) is passed over. When SYS, VIS or INV was given, a system file (bit 6) needs SYS, an invisible file (bit 3) INV, and any other VIS. The name and extension (+05H-+0FH, 11 bytes padded with spaces) are compared with the template at 56F0H, $ matching any character, and 55ABH turns the answer round after a minus sign. The name of a file taken is built at 57A4H as NAME/EXT ended by 03H and copied to 5784H for the displays.

5372H - Open the File on the Destination

The file specification gets .P3UF and :d: the password P3UF has the hash code 113DH, the same as RS0LT0FF, the password of the system files of LDOS, so an existing file on the destination opens even when it is protected. @OPEN with the buffer at 6800H tells whether the file exists (error 18H, File not in directory, when it does not). OLD takes only files that exist and NEW only those that do not.

53B6H - The Questions

Without QUERY=N CONV asks Convert file NAME/EXT? and, when the file exists on the destination, File exists -- replace it?; only an answer starting with Y (or y) takes the file, BREAK ends at @ABORT. The text at 5777H, Convert file and a space, has no end of its own: @DSPLY runs on into the copy of the name at 5784H and stops at its 03H. With QUERY=N CONV displays Converting file NAME/EXT.

540CH - Create the File and Set Its Length

A new file is created by @INIT as NAME/EXT:d, the password taken off again, with the record length of the TRSDOS 1.3 file; then bit 7 of the file control block's +01H and its +09H are cleared, so the file is written in whole sectors of 256 bytes. An existing file is written over from its start. The count of sectors is the ending record number of the record (+14H-+15H), plus one for a TRSDOS 1.3 file (version 13H or above) whose last sector is not full (EOF byte +03H not 00H). @POSN to the last of them and @WRITE give the file its whole length first; @REW goes back to the start.

547BH - Copy the Sectors

The sectors of the TRSDOS 1.3 file are read by 5501H into 6800H up, one page each, until the buffer reaches HIGH$ less 256 or the file ends; then the pages are written by @WRITE, each with +03H-+04H of the file control block pointed at it. At the end the EOF byte of the TRSDOS record goes into +08H of the file control block and @CLOSE writes the directory record.

54BCH - The Next Record and the Ends

54BCH steps 48 bytes to the next record; after the fifth record of a sector (offset F0H) it goes to the start of the next page, and after the last sector (6800H) CONV ends at @EXIT. 54DBH and 54DFH display their texts by @LOGOT and end at @ABORT; 54EBH (error 2CH) and 54EDH (the error in Register A) give the short message through @ERROR with bit 7 clear, which ends the program. Every end first puts the saved drive code table back at Index Register IY (54F5H); on the ways out from 54DBH, 54DFH and the parameter errors of 523AH-5253H the table has not been saved yet, and Index Register IY is whatever LDOS left in it, so 10 bytes from 57CDH-57D6H, beyond the file, are copied to that address.

5501H - Read the Next Sector of the TRSDOS 1.3 File

Called with Register Pair HL at the page to fill. The other register set keeps the count of sectors left (Register Pair DE), the sectors left of the current extent (Register B) and the next extent (Register Pair HL). An extent of a TRSDOS 1.3 record is two bytes: the track, then the first granule in bits 7-5 and the granules in bits 4-0; FFH as the track ends the list. A granule is three sectors, numbered from 1, so the first sector is granule x 3 + 1 and the extent has granules x 3 sectors. The next track and sector are kept at 57C6H-57C7H; after sector 18 comes sector 1 of the next track.

5558H - The Command Line Routines

5558H takes an optional drive (Register A = FFH without a colon), 555EH a required one (error 2CH without a colon or with a character that is not 0-7); 556FH passes over spaces; 5576H passes over and 557EH copies the characters of a name; 5588H tells whether Register A is a letter, a digit or $ (the Z FLAG), making a small letter a capital; 55A5H compares Register Pair HL with Register Pair DE; 55ABH turns the result of the name compare round after a minus sign.

55BBH - The List of the Files

Without a destination (or with DIR) the names are displayed in columns of 16 characters, a line holding four of them and ending at column 78 (4EH); the column and the line count are kept in the operand of LD HL at 55CFH. After 23 lines CONV waits for a key (ROM 0049H), moves the cursor up one line (1BH) and clears the rest of the screen (1FH), and counts again from the top.

560FH - The Parameter Table and the Texts

The table that @PARAM reads (8 bytes an entry: the name padded with spaces to 6 characters and the address of its operand, then 00H), the banner, the template and the texts.

5784H - The Work Areas Beyond the File

Not in the file: the copy of the name, the file control block, the drives, the next sector, the answer, the saved drive code table, the directory and the data buffer.