DOSPLUS 3.5 for the Model III - SYS9/SYS Disassembled

SYS9/SYS

Other Navigation

DOSPLUS 3.5 SYS9/SYS Disassembly - The Library Commands CAT, DIR and FREE (Model III)

SYS9/SYS is the first of the high overlays, which hold the library commands: it loads at 5200H, over the area 5200H-5BFFH that SYS0/SYS keeps for them, and holds CAT (request code 83H), DIR (84H) and FREE (85H). CMNDI@ takes these codes from SYS1/SYS's table of the library commands (51BDH, 51C6H and 51CDH) and passes them to the overlay request handler, which loads SYS9/SYS and calls routine 3, 4 or 5 of its table at 5200H with Register Pair HL at the rest of the command line. The file is a load module of 6 blocks, 1402 bytes, from 5200H to 577FH, with the transfer address 5200H; 56D5H-56DAH is not loaded (the digit buffer), and the work area, the output file's buffer and the directory buffer follow the file from 5780H. There are no patch blocks.

The Parts of SYS9/SYS

One Entry for Three Commands

The words of the routine table for CAT and DIR point one byte apart: DIR (520AH) starts with LD A,AFH, and CAT enters at its operand, 520BH, where the byte AFH reads as XOR A. So DIR stores AFH and CAT 00H to 53CFH, the operand of the LD DE,0000H at 53CEH that later selects DIR's long listing. FREE uses the same trick one instruction later: CAT and DIR run LD A,AFH at 521CH and FREE enters at its operand 521DH, so 531BH, the operand of LD A,00H at 531AH, is AFH for CAT and DIR (on to the file list) and 00H for FREE (on to the map). Only CAT and DIR clear the parameters.

The Command Line and the Output

EVAL@ (4479H) takes the command line with the block at 55D7H: a source drive (a name is error 2EH, Invalid parameter, and so is a device), a destination, a wildmask and the parameters INVIS, SYSTEM, KILL and ALPHA (55E0H), which may be shortened, given alone (FFFFH) or with =Y, =N and the like. Their values are stored straight into the operands of three LD DE,0000H instructions (540FH, 541DH, 542BH) and into 5781H. The output goes to the control block at 57A5H: the display (@DO) by default, a device named as the destination (LOCDCB% 44A0H gives its control block, stored under the type 90H), or a file, which INIT@ opens or creates with the buffer 5800H (56DBH); the file is closed at the end (5708H). Every character goes through the ROM's 001BH (561FH). The memory up to 5A00H, or 7A00H with ALPHA, must be below HMEM$ (4411HH), else error 21H, No memory space available. Errors are posted through ERROR@ with bit 6 set, so the message has no frame, and end the command (571AH).

The Drives

A drive named in the command is the only one shown, and an error 08H, Drive not available, when it is not ready. Without one, FREE shows every drive that is ready, 0 to 7, and CAT and DIR show drive 0, or every drive that is ready when a wildmask was given: this is the manual's global form, which finds a file on any drive (55B7H). Each drive starts with the summary line (5269H): Drive:, the drive's name from DCTTBL, the diskette's name from +D0H of the GAT, - Space:, the free directory entries (those without bit 4) and all the entries as nnn/nnn, and the free space as kilobytes with one decimal, such as 82.5k: the 0 bits of the GAT times the sectors per granule, divided by 4, the quarter left shown as .0, .2, .5 or .7 (5650H).

FREE's Map

FREE with a drive outputs a blank line and the map (532DH): one line for a group of cylinders, ccc-ccc:, then two spaces and a character for each granule: L when the granule is locked out (a bit of the lockout table at +60H of the GAT; a rigid drive has none), D for the granules of the directory on the directory cylinder, x for a granule in use and a period for a free one. A line holds seven cylinders, or six when a cylinder has seven granules or more, and the cylinders are two spaces apart, or one when they have five granules or more. The bit of a granule is tested by an instruction BIT n,(HL) whose bit number is stored into it (5611H).

CAT and DIR

The file list (53CBH) reads directory sectors 2 to the last. An extended entry is never shown, a deleted entry only with KILL, a system file only with SYSTEM, an invisible file only with INVIS (a deleted entry's other bits and a system file's invisible bit are not tested), an entry without a name never, and an entry that does not match the wildmask (WILD@, 5712H) is passed over (5403H). Each name is NAME/EXT in a column of 15 characters (5444H). CAT puts four names on a line. DIR heads the list with Filespec Attrib LRL #Secs #Recs Space Updated and gives each file a line (5476H, 54C2H): seven attribute characters (the protection level, then P, S, K, I, ! and +, or periods), the logical record length, the sectors written (+14H), the records, the kilobytes of the granules of all its extents (extended entries followed through 449AH) and the date of the last update as MM/DD/YY. The records are the whole sectors and the end of file byte divided by the record length, a part record counted as one. Numbers are made by the ROM's 132FH, five digits with leading zeros, and shown in a field of five or as two or three digits (5690H, 56C6H).

With ALPHA the list has two passes: the first reads the whole directory into memory, a sector to a page from 5900H, and SORT@ (4482H) sorts all its entries by their 11 bytes of name and extension, ascending; the second lists them from memory (5586H). The SPACE BAR pauses the output until the next key and BREAK ends it; neither is read while a DO file runs (563FH).

Differences from the Manual

The manual says FREE has no parameters; it takes the same four as CAT and DIR and ignores them, but since FREE does not clear 5781H, ALPHA still raises the memory it needs. The first number of the summary line counts the entries not in use (bit 4 clear, so deleted entries count as free), as the manual's description says; its example, which reads 080/128 as 80 of 128 used, has it the wrong way round. CAT shows system, invisible and deleted files only with their parameters, as the manual says, unlike CAT@ in SYS8/SYS.

Differences from the Model I

The code is the Model I SYS9/SYS at the same addresses; only the addresses in SYS0/SYS differ: HMEM$ is at 4411H (Model I 4049H), SFLAG1$ at 4297H (4302H), the system buffer at 4300H (4200H), DCTTBL at 44E8H (43ABH), and the calls go to the Model III entry points: 4488H DISKIO% (4485H), 44A3H LOCDCT% (448BH), 44A0H LOCDCB% (4488H), 444EH MULT@ (444BH), 4451H DIVD@ (444EH), 4494H the divide (4943H), 449AH the directory sector read (490CH) and 4485H the register saving wrapper (4525H).

5200H - The Routine Table

Data: SYS9/SYS's table of routines 2-5, one word each, used by SYS0/SYS's overlay request handler (its 49D3H-49E6H) for the request codes 82H-85H. CMNDI@ takes the codes of the library commands from SYS1/SYS's table: CAT 83H (51BDH), DIR 84H (51C6H), FREE 85H (51CDH). No file of the diskette requests 82H. The words for CAT and DIR point one byte apart, into the same instruction (520AH).

5208H - Routine 2

Nothing to do when SYS0/SYS's record locator brings SYS9/SYS back.

520AH - DIR, CAT and FREE

Routines 4 (DIR, 520AH), 3 (CAT, 520BH) and 5 (FREE, 521DH), entered from CMNDI@ through the overlay request handler with Register Pair HL at the rest of the command line. DIR stores AFH and CAT 00H to 53CFH, the operand of LD DE,0000H at 53CEH that selects the long listing; both clear the parameters INVIS, SYSTEM, KILL and ALPHA and store AFH to 531BH, the operand of LD A,00H at 531AH that sends them on to the file list. FREE enters at 521DH and stores 00H there, so it stays with the free space summary and map, and it does not clear the parameters. The command line is then evaluated by EVAL@ with the block at 55D7H: a source drive, a destination file or device, a wildmask and the parameters.

5269H - One Drive

The loop over the drives starts here with Register C = the drive. A drive that is not ready is an error when it was named (08H), else it is passed over. The GAT is read to 5900H, the drive's name and the diskette's name are put into the summary line, the free granules and the free directory entries are counted, and the line Drive: dd NAME - Space: free/total nnn.nk is output.

532DH - The Free Space Map

FREE with a drive: one line for each group of cylinders, ccc-ccc: followed by a character for each granule of each cylinder, L for a granule locked out (the lockout table at +60H of the GAT, not on a rigid drive), D for the directory's granules on the directory cylinder, x for a granule in use and . for a free one. A line holds seven cylinders, or six when a cylinder has seven granules or more, with two spaces between cylinders, or one when a cylinder has five granules or more. The SPACE BAR pauses the map and BREAK ends it (563FH).

53CBH - The File List of CAT and DIR

DIR outputs the heading line 573DH first; CAT and DIR then read directory sectors 2 to the last, one at a time into 5900H. With ALPHA the list is made in two passes: the first reads every directory sector into memory from 5900H, a page for each (53FDH, 5573H), SORT@ sorts all the entries by name and extension (558DH), and the second pass lists the entries from memory without reading. 53FEH holds the pass: FFH while reading, 00H while listing (and 00H without ALPHA).

5403H - An Entry

Register Pair HL = a directory entry in the buffer. An extended entry (bit 7) is never listed; an entry not in use (bit 4 clear) only with KILL; a system file (bit 6) only with SYSTEM; an invisible file (bit 3) only with INVIS; an entry with no name is passed over, and so is one that does not match the wildmask. The parameters are kept as the operands of three LD DE,0000H instructions, where EVAL@ stores the values.

5444H - The Name

NAME/EXT in a column of 15 characters: up to eight characters of the name (to the first space), a / when the extension does not start with a space, the three characters of the extension, then spaces to the 15th column.

5476H - The Attributes

DIR only. Seven characters: the protection level 0-7 (bits 2-0 of the flag byte), then P when either password code (+10H, +12H) is not 4296H, the code of a blank password, S for a system file (bit 6), K for a deleted file (bit 4 clear), I for an invisible file (bit 3), ! when the file may not shrink (bit 7 of +01H) and + when it was written to since its last copy or backup (bit 6 of +01H); a period for each that is not so. The letters are at 577AH.

54C2H - The Sizes

DIR only: the logical record length (1-256), the number of sectors (+14H), the number of records and the space the file's granules take in kilobytes, each as a number of up to five digits in a field of five, then the date of the last update.

5563H - The Next Entry

After each entry the SPACE BAR and BREAK are tested (563FH); BREAK ends the command. Then the next of the eight entries of the sector, then the next sector (or the next page of memory with ALPHA) up to the last directory sector.

55B7H - The Next Drive

A drive named in the command ends it. Without one, CAT and DIR go on to drives 1-7 only when a wildmask was given (the manual's global form); FREE goes on to every drive. Drives that are not ready are passed over (5274H).

55D7H - The Evaluation Block

Data: the 9 byte block EVAL@ (4479H) fills from the command line (5221H): the flags, then the addresses of the source, destination and wildmask blocks (33 bytes each, after the file at 5783H, 57A4H and 57C5H) and of the parameter table.

55E0H - The Parameters

Data: EVAL@'s parameter table, four 9 byte entries (a six character name, the address of the value, the type byte) and 00H at the end. Each type byte is 20H, a logical value: the name alone, or =Y, YES or ON, stores FFFFH; =N, NO or OFF 0000H; a name may be shortened to its first letters (the manual's S, I, K and A). FREE takes the same table: its map and summary do not look at the values, but ALPHA still raises the memory needed (5248H).

5605H - Output a Letter or a Period

Outputs the attribute letter at Register Pair DE when the C FLAG is set, else a period, and moves Register Pair DE to the next letter. Register Pair AF is kept, so the caller can go on rotating its flag byte.

5611H - Test a Granule's Bit

Register B = a granule 0-7, Register Pair HL = a byte of the GAT or the lockout table: returns the NZ FLAG when bit Register B of the byte is set. The bit number is put into the instruction BIT n,(HL) at 561CH (its second byte, 561DH).

561FH - Output a Character

561FH outputs a carriage return (0DH); 5621H outputs the character in Register A, through the control block at 57A5H: the display's or a device's (type 90H, made by 56F7H) or the file's that INIT@ opened (56EBH). The ROM's 001BH hands it to SYS0/SYS (4033H).

562AH - Output a Text

Outputs the text at Register Pair HL up to the 03H that ends it; Register Pair HL returns at the 03H.

5634H - Output Spaces

Outputs Register A spaces (Register A must not be 0); Register Pair AF returns with Register A = 00H.

563FH - The SPACE BAR and BREAK

Returns the Z FLAG when BREAK is pressed, else the NZ FLAG. While a DO file runs (bit 5 of SFLAG1$) the keyboard is not read. The SPACE BAR pauses until the next key, and that key may be BREAK.

5650H - Output Kilobytes

Register Pair HL = a number of sectors of 256 bytes: outputs it as kilobytes with one decimal (the sectors divided by 4, then .0, .2, .5 or .7 for the quarter left) and a k, such as 82.5k, the integer part in a field of five characters.

5670H - Output a Date

Register B = the month, Register C = the day (bits 7-3) and the year less 1980 (bits 2-0): outputs MM/DD/YY with two digits each, the year 80-87.

5690H - Output a Number

Register Pair DE = a number: 5690H outputs it as two digits, 5694H as three, both with leading zeros, and 5698H in a field of five characters with leading spaces. Register A is the count of leading zeros that may be left out (bit 7: put a space in place of each). The registers other than Register Pair AF are kept (4485H). The ROM's 132FH turns the number into five digits at 56D5H.

56C6H - A Number to Digits

Register Pair DE = a number, Register Pair HL = a buffer: the ROM's 132FH (FOUTCI) turns the integer at 4121H into five ASCII digits with leading zeros at Register Pair HL and a 00H after them; Register Pair BC = 0000H asks for no decimal point and no commas. Register Pairs BC and HL are kept.

56D5H - The Digit Buffer

Not in the file: no load block fills 56D5H-56DAH, which 569EH and the ROM's 132FH use for the digits of a number.

56DBH - Open the Output

The output goes to the display (@DO, device 1) unless a destination was given. A destination with a name or a drive (bit 6 or bit 3 of its flag byte at 57A4H) is a file: INIT@ opens or creates it with the control block at 57A5H (the destination's text) and the buffer 5800H. Any other destination is a device: its number (bits 0-2) goes to LOCDCB%, and its control block address and the type 90H are stored at 57A5H-57A7H. Returns the Z FLAG, or the NZ FLAG with INIT@'s error in Register A.

5708H - Close the Output

Closes the output file through CLOSE@ (4428H) unless the output is a device (type 90H). Returns the Z FLAG, or the NZ FLAG with CLOSE@'s error in Register A.

5712H - WILD@ When a Wildmask Was Given

Calls WILD@ (447CH) only when the command had a wildmask: with Register B not zero it sets the mask from the text at Register Pair HL, with Register B = 00H it compares the name at Register Pair HL with the mask (the NZ FLAG for no match). Without a wildmask it returns the Z FLAG: every name matches.

571AH - Posting an Error

571AH takes the error code from Register B, 571BH from Register A. Bit 6 is set, so ERROR@ (SYS5/SYS) displays the message without its frame; bit 7 is clear, so ERROR@ then ends the command through ABORT@.

5720H - The Summary Line

Data: the line Drive: dd NAME - Space: that starts each drive's output (52E8H), ended by 03H for 562AH. 5299H-52A7H put the drive's name and the diskette's name into it; the file holds NS and diskname there.

573DH - DIR's Heading

Data: the heading line of DIR's columns (53CBH), ended by 0DH and 03H.

577AH - The Attribute Letters

Data: the six letters of DIR's attributes after the protection level, output by 5605H in this order, a period for each that does not hold.

5780H - The Work Area

Not in the file: SYS9/SYS uses the memory after its last byte (577FH) for its counters, the three blocks of EVAL@, the output file's buffer and the directory buffer.