Percom DoubleDOS 4.24 for the Model I - SYS6/SYS Disassembled

SYS6/SYS

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Percom DoubleDOS 4.24 SYS6/SYS Disassembly (Model I)

SYS6/SYS holds the library commands of DoubleDOS (DBLDOS in Percom's manual). It is overlay 8 (directory record 20H), loaded at 5200H by the overlay dispatcher of SYS0/SYS (4BA2H) for request code 88H, which SYS1/SYS gives when a command line starts with one of the 19 names of its library table (SYS1/SYS 4E90H). SYS1/SYS sets bit 4 of 430FH when it loads SYS6/SYS, and while that bit is set it jumps to 5200H without loading it again; it clears the bit before it runs a program. Register C is the number of the command, Register Pair HL the rest of the command line. SYS1/SYS is still in memory at 4E00H while a command runs, and SYS6/SYS uses its parameter list parser (4476H, request code E3H) and its option reader at 51A0H; PROT, FREE, ATTRIB and RENAME open a file first so that SYS2/SYS is loaded at 4E00H and its password hash, name hash, drive test and hash index table routines can be called.

The file is 3361 bytes: a name record, the copyright record of 169 bytes, seven load blocks, 5200H-52DBH, 52DFH-5550H, 5591H-55BAH, 5700H-590DH, 5914H-59EDH, 5B00H-5E66H and 5E6AH-60CCH (3114 bytes), and the transfer address 5200H. The gaps between the blocks are the variables and buffers of the commands; each is a DEFS row below. Every loaded byte is on exactly one row. SYS6/SYS is the same in DoubleDOS 4.20, 4.23 (all three sets) and 4.24.

Every command ends at DOS READY: 5200H pushes 402DH before it jumps, so a RET or JP 402DH returns there. Errors of the file routines go to 554CH, which sets bit 6 of the code and jumps to @ERROR (4409H): SYS4/SYS shows the message and ends at 4030H, the abnormal exit (DEBUG when it is on). The commands' own messages are shown by 4467H and also end at 4030H.

Load Map

Addresses	Contents
5200H-5250H	Pick the command by its number (5200H)
5251H-5282H	RESERVED COMMAND and -NOTHING DONE- (5251H, 526BH)
5283H-52D2H	AUTO, DATE, TIME and CLOCK (5283H)
52D3H-531CH	BAD FORMAT; the three numbers of DATE and TIME (52EAH)
531DH-5339H	The reserved command double; unused code (5320H)
533AH-5369H	LIB (533AH)
536AH-5503H	PROT, its password input and its texts (536AH)
5504H-5514H	VERIFY (5504H)
5515H-5539H	The test for BREAK and the pause key (5515H)
553AH-5550H	FILE SPEC REQUIRED, an unused exit, and the report of an error (553AH)
5551H-5590H	Not in the file: the two FCBs, 5551H and 5571H
5591H-55BAH	Texts
55BBH-56FFH	Not in the file: the buffer 5600H-56FFH
5700H-57D6H	APPEND, with the remains of an earlier APPEND (5700H)
57D7H-5913H	DUMP (57D7H)
5914H-59EDH	KILL, LIST, LOAD and PRINT (5914H)
59EEH-5AFFH	Not in the file
5B00H-5C6EH	ATTRIB (5B00H)
5C6FH-5EDFH	DIR (5C6FH)
5EE0H-5F9BH	FREE (5EE0H)
5F9CH-606BH	RENAME (5F9CH)
606CH-60CCH	Write a number in decimal; divide a three byte number (606CH, 60A7H)

The Commands

No. Entry	Command
1 5700H	APPEND file1 TO file2 Both files must exist. file2 is positioned at its end and file1 is copied to it byte by byte (BREAK stops it). Both files are closed.
2 5B00H	ATTRIB file (I, PROT=level, ACC=password, UPD=password) Only the first letter of a word counts. Levels by their first two letters: EX(EC) 6, RE(AD) 5, WR(ITE) 4, NA(ME) and REN(AME) 2, KI(LL) 1, FU(LL) 0. The attribute byte gets the level given (else 0) and the invisible bit when I is given (else none); a password hash is stored only when it is given.
3 5283H	AUTO command 32 bytes from the command line to GAT bytes E0H-FFH of drive 0; AUTO alone turns the automatic command off.
4 52C5H	CLOCK [(OFF)] The clock display task 4CA9H of SYS0/SYS in task slot 6, or out of it.
5 5251H	copy (reserved) RESERVED COMMAND. SYS1/SYS never matches the name in small letters, so COPY runs COPY/CMD.
6 529DH	DATE MM/DD/YY To 4046H (month), 4045H (day), 4044H (year).
7 531DH	double (reserved) Does nothing; DOUBLE runs DOUBLE/CMD.
8 5C6FH	DIR [:d] (A, I, S) Three files a line with S, I and P marks; A adds LRL, EOF and SIZE; I and S show invisible and system files. Twelve lines to a screen.
9 57D7H	DUMP file (START=, END=, TRA=) Memory from START to END as a load module, default extension CIM. START and END default to 7000H, TRA to 402DH; START must be 7000H or more.
10 5EE0H	FREE For each drive that turns: name, date, free directory places (FILES) and free granules (GRANS).
11 5914H	KILL file Opened and removed by @KILL.
12 533AH	LIB The 19 names of SYS1/SYS's library table, four a line.
13 592CH	LIST file (LINE=n) The file on the screen; LINE has no effect (bug B29).
14 5994H	LOAD file @LOAD, without running the program.
15 59ACH	PRINT file The file to the printer through ROM 003BH.
16 536AH	PROT [:d] (PW, LOCK, UNLOCK) After the master password (GAT bytes CEH-CFH): PW asks for a new one; LOCK gives every visible file the master password as both passwords, UNLOCK the blank password. Refused while the chaining flag (430FH bit 5) is set.
17 5F9CH	RENAME file1 TO file2 file2 without a drive, on file1's drive, must not exist; the name in the entry and its HIT byte are changed.
18 52B1H	TIME HH:MM:SS To 4043H (hours), 4042H (minutes), 4041H (seconds).
19 5504H	VERIFY [(OFF)] The @WRITE vector 4439H to @VERF 47A8H, or back to 478BH.

The options (OFF), (NO) and (N) of CLOCK and VERIFY are read by 51A0H of SYS1/SYS, the routine of DEBUG; no option or any other turns the function on. The parameter lists of PROT, DUMP, LIST and DIR are read by 4476H, whose table entries hold a name of six characters and the address of a word; a parameter named alone gets FFFFH. Typed in full, UNLOCK fills the six bytes of SYS1/SYS's name buffer, so that its 03H lands on the C of CMD (SYS1/SYS bug B8): a program command after PROT (UNLOCK) gets a wrong default extension while SYS1/SYS is not loaded again.

APPEND, LIST, PRINT and DIR call 5515H between bytes or lines: BREAK held stops the command, SHIFT and @ (60H) waits until another key or BREAK. The test is passed over while the chaining flag is set.

Bugs

No. Address	What happens
B27 52B1H	DATE and TIME check only that each number has two digits. A time such as 25:70:99 is taken: the clock task of SYS0/SYS counts each part up until it equals 60, 60 or 24, so a part above that runs on to 255 and round through 0 before the time is right again. A month of 13 or a day of 40 is stored as it is.
B28 5469H	When exactly eight characters are typed at MASTER PASSWORD ? or NEW MASTER PASSWORD ?, the count of the spaces to add is 00H and the DJNZ writes 256 spaces at 5608H-5707H, over the first eight bytes of APPEND at 5700H. SYS6/SYS stays marked as in memory (430FH bit 4), so an APPEND typed before any program runs jumps into the spaces, 20H 20H, a chain of JR NZ instructions.
B29 5942H	LIST loads its parameter table 598BH into Register Pair BC, but the parser 4476H takes its table from Register Pair DE, which still holds 5551H, the file specification. LINE is never found, so LIST always starts at the first line; a parameter whose name happens to match the first characters of the specification would have its value stored at an address made of the specification's characters.
B30 595AH	The loop that passes over LINE lines (never run, B29) does not test the end of the file, so a file with fewer lines would never leave it; and with Register C not 00H it passes over C + 256 x (B - 1) lines instead of the count in Register Pair BC.
B31 583AH	DUMP does not test the result of any output of 001BH: when the diskette is full, the rest of the bytes are lost, the file is closed and DOS READY follows with no error.
B32 58BEH	END LESS THAN START and START LESS THAN X'7000' are found only after the file has been opened or made and its name record written to the buffer; the file is never closed, so a new file stays in the directory empty.
B33 5DF1H	DIR (A) takes the file's bytes as the sectors of entry +14H-+15H times 256 plus the end of file byte, but those sectors include the last, partly used one: for a file whose end of file byte is not 00H, EOF= is 256 bytes' worth of records too many (with LRL 1, 256 too many).
B34 60BBH	The division of DIR (A) shifts the remainder left in Register A with RLA and drops the bit carried out. For a record length of 129-255 a remainder of 128 or more loses its top bit, so EOF= is wrong for such files.
B35 5398H	PROT tests only the low bytes of the words of PW, LOCK and UNLOCK to see whether one was given; a value with a low byte of 00H (for example LOCK=256) gives -NOTHING DONE-, although 53D8H-5407H test both bytes.
B36 538AH	PROT and DIR (5C88H) take any character after the colon as a drive: :4 to :9 and other characters give drive numbers above 3, for which 4B55H reads the directory block from a byte past the table 4304H-4307H. SYS2/SYS refuses such drives (error 20H), but these two commands do not call it for the drive.

Every bug found in DoubleDOS is listed, with what a user would do to set it off, on the DoubleDOS reference page.

Differences From the Manual

Percom's manual says that every TRSDOS command is available under DBLDOS except DEVICE, FORMAT and BACKUP, and that COPY is enhanced; for the commands themselves it refers to the TRSDOS manual. SYS6/SYS agrees: its table has no DEVICE, FORMAT or BACKUP, and its copy and double entries are reserved, so that COPY/CMD and DOUBLE/CMD run instead. Nothing in the manual describes the library commands, so nothing on this page is compared with it.

Notes

Places in SYS6/SYS

Most variables of the commands are the operands of instructions (self-modifying code), set before the instruction runs.

Address Size	Contents
52DCH-52DEH 3 bytes	The Three Numbers of DATE and TIME Not in the file. Stored by 52F5H in reverse order, copied to 4044H or 4041H.
53BCH 1 byte	PROT's Drive The operand of LD C at 53BBH, stored by 538FH, read by 53EBH and 540FH.
53D9H, 53F9H, 5403H 2 bytes each	PW, LOCK, UNLOCK The operands of LD DE at 53D8H, 53F8H and 5402H: cleared by 5372H-537DH, set by the parser.
5430H-5431H 2 bytes	The Password Hash PROT Gives The operand of LD DE at 542FH, stored by 540CH.
5551H-5570H 32 bytes	The First FCB Not in the file. The file of every command; 5552H (access), 5557H (drive), 5558H (directory record), 5559H-555AH.
5571H-5590H 32 bytes	The Second FCB Not in the file. file2 of APPEND, the new name of RENAME.
5600H-56FFH 256 bytes	Buffer Not in the file. The sector buffer of the first FCB for APPEND, DUMP, LIST and PRINT; the password typed for PROT (5600H-5607H, and 5608H-5707H in bug B28).
5868H, 586EH, 58ABH 2 bytes each	START, END, TRA The operands of LD HL at 5867H, 586DH and 58AAH: 7000H, 7000H and 402DH from 57DAH-57E5H, set by the parser.
590EH-5913H 6 bytes	DUMP's Name Record Not in the file. Made by 5806H-5822H.
5954H-5955H 2 bytes	LINE The operand of LD BC at 5953H, cleared by 592FH; never set (bug B29).
5C05H 1 byte	ATTRIB's Parts Given The operand of LD D at 5C04H: bit 0 PROT, bit 1 ACC, bit 2 UPD (5B84H-5B88H).
5C0BH 1 byte	ATTRIB's Protection Level The operand of OR at 5C0AH, stored by 5B7EH.
5C0DH 1 byte	ATTRIB's Invisible Bit The operand of OR at 5C0CH: 08H when I is given (5BA2H).
5CFDH, 5D0BH, 5D9BH 2 bytes each	S, I, A of DIR The operands of LD DE at 5CFCH, 5D0AH and 5D9AH: cleared by 5C72H-5C7AH, set by the parser.
5DABH 1 byte	DIR's Lines Left The operand of LD A at 5DAAH: 0CH from 5CE7H and after each wait.
5E1FH 1 byte	The Record Length of DIR (A) The operand of LD C at 5E1EH, stored by 5DFDH.
5E67H-5E69H 3 bytes	The Bytes of a File Not in the file. High byte first: entry +15H, +14H, +03H (5DF6H, 5E13H, 5E18H).
5E9EH, 5F68H 1 byte each	The Drive Digits In the texts of DIR and FREE (5C8FH, 5EF4H). The name, date and numbers of their lines are also written into the texts.

Other Memory

Address Size	Contents
4041H-4043H 3 bytes	The Time Seconds, minutes, hours, set by TIME (52C2H).
4044H-4046H 3 bytes	The Date Year, day, month, set by DATE (52AEH).
4200H-42FFH 256 bytes	Directory Sector Buffer Directory sectors of PROT, DIR (and its GAT), ATTRIB and RENAME (4AC1H, 4B35H).
430FH 1 byte	Flags Bit 5 (chaining) read by 536AH and 5515H; set by no file.
443AH-443BH 2 bytes	The @WRITE Vector 478BH or 47A8H, set by VERIFY (550FH).
4D00H-4DFFH 256 bytes	GAT or HIT The GAT of AUTO, PROT and FREE (4AF0H), the HIT of FREE and RENAME (512EH); 4DCEH-4DCFH the master password hash, 4DD0H the name, 4DD8H the date, 4DE0H-4DFFH the AUTO command.
5155H-516BH 23 bytes	SYS2/SYS's Work Area 5155H-515CH a value of ATTRIB; 515DH-5167H the name and extension parsed for RENAME; 5168H-5169H and 516AH-516BH password hashes.
6100H-68FFH 2048 bytes	DIR's Copy of the Directory Eight sectors, cleared at the end (5DE1H); 6100H-61FFH is also file2's buffer of APPEND.

Outside Routines

Address	Use
0013H, 001BH	ROM: Input and Output of a Byte To and from a file through the device vector: APPEND, DUMP, LIST, PRINT.
002BH, 0040H, 0049H	ROM: Keyboard Scan, Line Input, Wait for a Key 5515H; PROT's password (5459H); DIR (5DAFH).
0033H, 003BH	ROM: Show a Character, Print a Character Most output; PRINT.
4410H, 4413H	SYS0/SYS: Add or Remove a Task CLOCK.
441CH, 4420H, 4424H, 4428H, 442CH, 4430H, 4436H, 4439H, 4448H, 4473H, 4476H	SYS0/SYS Vectors Parse a file specification, open or make, open, close, kill, @LOAD, @READ, @WRITE, @PEOF, add an extension, parse a parameter list.
4409H, 4467H, 402DH, 4030H	SYS0/SYS: @ERROR, Show a Text, DOS READY, Abnormal Exit
45CFH, 4AC1H, 4AD6H, 4AF0H, 4B03H, 4B35H, 4B55H	SYS0/SYS: The Directory Write a directory sector, read and write a directory record, read and write the GAT, read a directory sector, the directory block of a drive.
51A0H	SYS1/SYS: Read an ON or OFF Option CLOCK, VERIFY.
5081H, 509BH, 50D1H, 50FDH, 512EH, 5141H	SYS2/SYS Copy a part, name hash, password hash, drive test, read and write the HIT.

5200H - Run a Library Command

The transfer address of SYS6/SYS, overlay 8 (directory record 20H), loaded at 5200H by the overlay dispatcher of SYS0/SYS for request code 88H, which SYS1/SYS gives at 4EA0H for a library command; when SYS6/SYS is still in memory (bit 4 of 430FH) SYS1/SYS jumps to 5200H directly (4E95H). Register C is the number of the command in SYS1/SYS's table at 4EBDH (1 APPEND to 19 VERIFY) and Register Pair HL the rest of the command line. The address 402DH is pushed first, so that each command ends at DOS READY by its RET; a chain of DEC A picks the routine.

5251H - Reserved Command

Command 5 (copy) and any number above 19 come here. The table of SYS1/SYS spells copy in small letters, which its lookup never matches, so that COPY runs COPY/CMD; this entry is never reached from SYS1/SYS.

526BH - Nothing Done

PROT comes here when no parameter was given and ATTRIB when no list in parentheses follows the file specification.

5283H - AUTO: Store the Command to Run at Start-Up

The rest of the command line, 32 bytes from Register Pair HL, is copied to bytes E0H-FFH of the GAT of drive 0. At start-up SYS0/SYS runs that text unless its first byte is a carriage return (SYS0/SYS 4EDDH), so AUTO with nothing after it turns the automatic command off. The 32 bytes are copied whatever they hold: the line's carriage return and the bytes after it in the command line buffer 4318H-4357H go too.

529DH - DATE: Set the Date

The text after DATE must be MM/DD/YY, three numbers of two digits separated by slashes. 52EAH reads them into 52DCH-52DEH in reverse order, so that the year goes to 4044H, the day to 4045H and the month to 4046H. No number is checked against its range.

52B1H - TIME: Set the Time

The text after TIME must be HH:MM:SS, three numbers of two digits separated by colons, read into 52DCH-52DEH in reverse order: the seconds go to 4041H, the minutes to 4042H and the hours to 4043H, the counters of the clock task of SYS0/SYS (45AFH). No number is checked against its range: the clock task counts each one up until it equals 60, 60 or 24 (45CCH), so a number above that runs on to 255 and round through 0 first (a bug: the Bugs part of the introduction).

52C5H - CLOCK: Show the Time or Stop Showing It

CLOCK alone (or with an option that is not OFF or NO) puts the clock display task 4CA9H of SYS0/SYS in task slot 6, so that the time is shown at the right end of the top line of the screen; CLOCK (OFF) or CLOCK (NO) takes it out. The option is read by 51A0H of SYS1/SYS, which is still in memory at 4E00H.

52D3H - Bad Format

DATE and TIME come here when their text is not three numbers of two digits with the right separators.

52EAH - Read Three Numbers

Called by DATE and TIME with Register Pair HL the text and Register C the separator. Three numbers of exactly two decimal digits each are read; the first goes to 52DEH, the second to 52DDH and the third to 52DCH. Returns the Z FLAG when the three numbers and the two separators were found; nothing after the third number is looked at.

52FFH - Read a Number of Two Digits

Reads two characters at Register Pair HL and returns their value 0-99 in Register A with the Z FLAG, or the NZ FLAG when one of them is not a digit.

5316H - Read One Digit

Returns Register A the character at Register Pair HL minus 30H, Register Pair HL past it, and the C FLAG when the character is a digit 0-9.

531DH - The Reserved Command double

Command 7, double in small letters in the table of SYS1/SYS, which never matches it: DOUBLE runs DOUBLE/CMD. The entry only goes to DOS READY.

5320H - Unused Code: Show a Table of Two Letter Names

Nothing in DoubleDOS jumps to 5320H-5339H. The bytes are a routine that would go through a table at Register Pair HL of four byte entries within one page: for each entry whose first byte is not 00H it shows two characters and a carriage return. They are shown as instructions.

533AH - LIB: Show the Library Commands

The names of the 19 entries of SYS1/SYS's table of library commands (4EBDH, eight bytes an entry: six characters and the address 4E90H) are shown four to a line, each after two spaces and followed by eight. SYS1/SYS is still in memory at 4E00H when SYS6/SYS runs. The reserved commands copy and double are shown in small letters as they are in the table.

536AH - PROT: Change the Master Password, Lock or Unlock a Diskette

PROT [:d] (PW, LOCK, UNLOCK). The master password of the diskette, whose hash is kept in GAT bytes CEH-CFH, must be typed first. PW asks for a new master password; LOCK gives every visible file of the diskette the master password as both its passwords, UNLOCK gives them the blank password. The routine refuses to run while bit 5 of 430FH, the chaining flag, is set; no DoubleDOS file sets it. To have the password hash of SYS2/SYS (50D1H) in memory, it opens an empty file specification, which loads SYS2/SYS at 4E00H and fails.

5454H - Read a Password and Hash It

Shows nothing itself: the caller has shown the prompt. Up to eight characters are read by the ROM's line input into 5600H, the rest is filled with spaces and 50D1H of SYS2/SYS, which PROT has loaded at 4E00H, returns the hash in Register Pair HL. When exactly eight characters are typed, Register B is 00H for the fill and DJNZ writes 256 spaces at 5608H-5707H, over the first bytes of APPEND at 5700H (a bug: the Bugs part of the introduction). BREAK is not tested.

546EH - Invalid During a Chain

PROT comes here when bit 5 of 430FH is set.

5504H - VERIFY: Read Back Every Sector Written

VERIFY alone (or with an option that is not OFF or NO) makes @WRITE (4439H) jump to 47A8H, @VERF, which writes each sector and reads it back; VERIFY (OFF) puts back 478BH, the plain write. The option is read by 51A0H of SYS1/SYS.

5515H - Test for BREAK and the Pause Key

Called by APPEND, LIST, PRINT and DIR between characters or lines. While the chaining flag (430FH bit 5) is set it returns the Z FLAG at once. Otherwise BREAK held returns the NZ FLAG (stop); SHIFT and @ (the code 60H) waits until BREAK (NZ) or another key is pressed (Z, the key is dropped); no key or another key returns the Z FLAG (go on).

553AH - File Specification Required

The commands come here when the file specification cannot be parsed or names a device (it starts with an asterisk).

5543H - Unused: Device Specification Required

Nothing in DoubleDOS jumps to 5543H: no command of SYS6/SYS needs a device. The text 55A5H is shown by nothing.

554CH - Report an Error

Every disk error of the commands comes here with the error code in Register A. Bit 6 is set and @ERROR (4409H) is called through a jump: SYS4/SYS shows the message, and as bit 7 is clear it ends at 4030H, the abnormal exit.

5700H - APPEND: Add One File to the End of Another

APPEND file1 TO file2 (the word TO is passed over by the file specification parser of SYS1/SYS). Both files must exist. file2 is opened with its buffer at 6100H and positioned at its end, file1 with its buffer at 5600H; then file1 is copied byte by byte to the end of file2 until its end, BREAK, or an error. Both files are closed.

5748H - Unused: Remains of an Earlier APPEND

Nothing jumps to 5748H-57A0H. 5748H is the high byte of a CALL 4448H whose first bytes have been overwritten by the jump at 5745H; then come a test and a jump that end as at 5742H-5745H, and an earlier form of the command that copies sector by sector with @READ and @WRITE and makes file2 when it does not exist. They are shown as instructions; 57A1H is used again.

57A1H - Close Both Files

The end of APPEND: file2 and then file1 are closed.

57B6H - Copy the Bytes

Each byte of file1 is taken by the ROM's 0013H and put into file2 by 001BH; both go through the device vector to SYS0/SYS's byte input and output of a file. The end of file1, or BREAK (5515H), closes both files.

57D7H - DUMP: Write Memory to a Program File

DUMP file (START=, END=, TRA=). The memory from START to END is written to the file (default extension CIM, made when it does not exist) as a load module: a name record of the first six letters and digits of the name, load records of 254 bytes at most, and a transfer record of TRA. START and END are 7000H and TRA 402DH (DOS READY) unless given; START must be 7000H or more and END not below START. The results of the writes of 001BH are not tested (a bug: the Bugs part of the introduction).

5914H - KILL: Remove a File

KILL file. The file is opened (with the record length and buffer left in Register B and Register Pair HL by the parser, which @KILL does not use) and removed by @KILL, which frees its granules and its directory entries.

592CH - LIST: Show a File on the Screen

LIST file (LINE=n). The file is shown byte by byte through the ROM's display until its end; BREAK at the end of a line stops it, SHIFT and @ pauses. LINE was meant to pass over the first lines, but its table 598BH is put in Register Pair BC, while the parser takes its table in Register Pair DE, which still holds 5551H, the file specification: LINE is never found and stays 0000H (a bug: the Bugs part of the introduction). The skip loop 5953H-5965H is therefore never run.

5994H - LOAD: Load a Program Without Running It

LOAD file. @LOAD reads the load module into memory; the command then goes to DOS READY.

59ACH - PRINT: Send a File to the Printer

PRINT file. The file is sent byte by byte to the printer through the ROM's 003BH until its end, with a carriage return after it; BREAK stops it, SHIFT and @ pauses.

5B00H - ATTRIB: Set the Attributes and Passwords of a File

ATTRIB file (I, PROT=level, ACC=password, UPD=password); only the first letter of each word is looked at. The file is opened (SYS2/SYS stays in memory at 4E00H with its work area 5155H-516BH), the list is read, and the file's directory entry gets: the protection level when PROT is given, else level 0; the invisible bit when I is given, else none; the access or update password hash only when ACC or UPD is given. The passwords are hashed by 50D1H of SYS2/SYS; SYS2/SYS never tests them when it opens a file (SYS2/SYS bug B13).

5B3AH - Read the Next Word of the List

Register Pair HL is at the opening parenthesis or a comma. The first letter picks the word: I, A (access), U (update) or P (protection); any other gives ATTRIBUTE SPECIFICATION ERROR.

5BD1H - Find the Value of a Word

Called with Register Pair HL at the first letter of the word. The rest of the word is passed over up to an equals sign; a carriage return, closing parenthesis or comma first returns the Z FLAG (no value) with Register Pair HL at it. After an equals sign up to eight letters and digits (the first a letter) are copied to 5155H, padded with spaces, by 5081H of SYS2/SYS; the NZ FLAG is returned with Register Pair HL at the character after the value.

5BF7H - Change the Directory Entry

The entry of the file is read, its attribute byte is rebuilt from bits 7-4 and the parts given, the password hashes given are stored, and the entry is written back.

5C39H - Attribute Specification Error

Every fault in ATTRIB's list comes here.

5C6FH - DIR: Show the Directory

DIR [:d] (A, I, S). The heading FILE DIRECTORY --- DRIVE d is shown at the top of a cleared screen, then the diskette's name and date from its GAT. The eight directory sectors are copied to 6100H-68FFH, and the entries are shown three to a line in the order of the hash index table: entry 0 of every sector, then entry 1, and so on. A file shows its NAME/EXT, then S for a system file, I for an invisible one and P when it has passwords; system files only with S, invisible ones only with I. With A every file has a line of its own with LRL, EOF (the records) and SIZE (the granules). After twelve lines DIR waits for a key; BREAK stops it. The copy at 6100H-68FFH is cleared at the end.

5CECH - Show One Entry

Register Pair HL is the entry in the copy at 6100H-68FFH, Register B the places left on the line. An entry is passed over when it is not in use (bit 4 of its attribute clear), when it is an extra entry (bit 7), when it is a system file (bit 6) and S was not given, or when it is invisible (bit 3) and I was not given.

5DBFH - Go to the Next Entry

The same entry of the next sector page comes next; after page 68H, the next entry of the first page.

5DE1H - Clear the Copy of the Directory

Writes 00H in 6100H-68FFH: no copy of the directory entries, with their password hashes, stays in memory after DIR.

5DF1H - Show LRL, EOF and SIZE

Called for DIR (A) with Register Pair HL the entry. LRL is the record length (256 for 00H); EOF is the number of records, the three byte number at 5E67H-5E69H (the sectors of entry +14H-+15H times 256, plus the end of file byte of entry +03H) divided by the record length; SIZE is the granules of all the file's extents. Entry +14H-+15H counts the last sector even when it is only partly used, so EOF is 256 bytes too large for a file whose end of file byte is not 00H (a bug: the Bugs part of the introduction). Returns Register B 01H.

5E3EH - Count the Granules of a File

Called with Register Pair HL the entry in the copy at 6100H-68FFH. The granule bytes of the extents at +16H-+1FH are added up (bits 4-0 plus 1 each); FEH and a record go on to the extents of the extra entry (its sector page 61H plus bits 2-0, its place bits 7-5), FFH ends. Returns Register Pair DE the granules.

5EE0H - FREE: Show the Free Space of Each Drive

For drives 0-3 a line DRIVE d -- NAME MM/DD/YY nnnnn FILES, nnnnn GRANS: the diskette's name and date from the GAT, the free directory places (HIT bytes 00H in entries 2-7 of the eight sectors, the places of ordinary files) and the free granules (the 0 bits of GAT bytes 00H-BFH). A drive whose index pulses 50FDH of SYS2/SYS does not see is passed over. To have SYS2/SYS's routines in memory, an empty file specification is opened first, which loads SYS2/SYS and fails.

5F9CH - RENAME: Give a File a New Name

RENAME file1 TO file2. file1 is opened; file2 must have no drive of its own, gets file1's drive and must not exist. The open of file2 leaves its name and extension parsed at 515DH in SYS2/SYS's work area: they replace the name in file1's directory entry, and file1's HIT byte gets the hash of the new name. The passwords of the entry stay as they were.

606CH - Write a Number in Decimal

Called with Register Pair HL the number (0-65535) and Register Pair DE the place. Five characters are written: the ten thousands, thousands, hundreds and tens as digits once one of them is not 0, spaces before that, and the units always as a digit. Register Pair DE returns past them.

608CH - Write One Place

Register A is the character for 0 (a space until a digit has been written, then the digit 0), Register Pair BC the value of the place. The place is subtracted from Register Pair HL as often as it goes; the count is written as a digit, or Register A when it is 0. Returns Register A 30H once a digit has been written.

60A7H - Divide a Three Byte Number

Called with Register Pair HL three bytes, high byte first, and Register C the divisor. Returns Register Pair DE the quotient (its low 16 bits). For Register C 00H (256) the quotient is the first two bytes. The remainder is kept in Register A and shifted left with RLA: when Register C is above 80H, a remainder of 80H or more loses its top bit, and the quotient is wrong (a bug: the Bugs part of the introduction).