TRS-80 DOS - NEWDOS/80 v2.0 for the Model I - ASPOOL/MAS Disassembled

ASPOOL/MAS

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Purpose

ASPOOL is a sophisticated print spooler for the TRS-80 that intercepts printer output, buffers it to disk files, and prints it in the background. This allows users to continue working while documents print, effectively providing multitasking for printer operations.

Key Features:

• Background Printing: Captures printer output to disk, allowing programs to continue running
• Multiple Pool Files: Supports up to 5 separate spool files (POOL_:1 through POOL_:5)
• Multi-Interface Support: Works with RS-232 serial, Model III parallel port, or Model I expansion interface hardware ports
• Flexible Configuration: Interactive installation with 13+ configuration options
• Self-Relocating Code: Automatically positions itself in high memory below HIGH$
• Form Feed Handling: Soft form feed (sending multiple line feeds) or hard form feed (0CH character)
• Page Management: Configurable lines per page with automatic page breaks
• Timeout Detection: Configurable delay after last keystroke before printing
• DOS Integration: Intercepts DOS printer vectors for seamless operation
• Buffer Management: 256-byte circular input buffer (5440H-5540H) and 256-byte output buffer (5300H-5400H)

Operation Modes:

• Spool Mode (W command): Captures printer output to disk files
• Print Mode (P command): Prints spooled files to physical printer
• Status Mode (no command): Displays current spooling/printing status
• Clear Mode (C command): Clears backlog or activates printing
• Stop Mode (S command): Stops spooler operation
• Install Mode (I command): Interactive configuration and installation
• Purge All Mode (A command): Deletes all pool files

Technical Highlights:

• Self-Modifying Code: Extensive use of runtime code modification for configuration
• Address Relocation: Sophisticated scanner that relocates all absolute addresses during installation
• System Vector Interception: Hooks into NEWDOS/80 keyboard break (4026H) and system vectors (4016H)
• Memory Protection: Adjusts HIGH$ (4049H) to protect spooler from BASIC memory allocation
• Hardware Port I/O: Direct control of printer ports (E8H, E9H, EAH, EBH) with baud rate configuration
• Circular Buffering: Efficient keyboard input buffering during print operations
• DOS Integration: Uses NEWDOS/80 file I/O routines (4413H, 4420H, 4424H, 4428H, etc.)

Instructions/Command Line:

Command	Syntax	Description
ASP	ASP	Display current spool status (spooling count, printing status, backlog)
ASP P	ASP P	Activate printer - start printing spooled files to physical printer
ASP S	ASP S	Stop spooler - halt all spooling and printing operations
ASP C	ASP C	Clear - prompt to clear backlog (B) or activate printing (P)
ASP W	ASP W	Write mode - begin capturing printer output to spool files
ASP I	ASP I	Install - interactive configuration and installation to disk
ASP A	ASP A	purge All pool files - delete all POOL_:n files (1-5)

NEWDOS/80 System Vectors

Address	Type	Description
4016H	Word	System pointer - modified to point to printer buffer check routine (5661H relocated)
4026H	Word	Keyboard break vector - modified to point to spooler return (550BH relocated)
4041H	Byte	System clock seconds (used for timeout calculation)
4042H-4043H	Word	System clock minutes:hours (used for timeout calculation)
4049H	Word	HIGH$ - top of available memory, adjusted to protect spooler
4121H	Byte	Numeric conversion result (used by 0E6CH routine)
4369H	Byte	DOS mode flags (bit 6 = in DOS mode indicator)

Pool Status and Configuration

Address	Type	Description
5534H	Byte	Active spool count (number of files currently being spooled)
5766H	Byte	Printer active flag and pool number (00H=inactive, 01-05H=active pool)
5822H	Byte	Pool number character in filename template ('1'-'5')
5824H	Byte	Display template pool number
5828H-582CH	5 Bytes	Pool status table (00H=empty, 01-FEH=file count)
582DH	Byte	Pool table end marker (FFH)
582EH	Byte	Line feed counter for form feed calculations
582FH	Byte	Column position flag (00H=start of line, 01H=content on line)

File Control Blocks

Address	Type	Description
5420H	32 Bytes	Spool file FCB (POOL_:n files for capturing output)
5400H	32 Bytes	Printer file FCB (reading spool files for printing)

Buffer Areas

Address	Type	Description
5200H-5300H	256 Bytes	Printer input buffer (reading from spool files)
5300H-5400H	256 Bytes	Printer output buffer (capturing output to spool)
5440H-5540H	256 Bytes	Keyboard input circular buffer (monitoring input during print)

Configuration Flags

Address	Type	Description
5792H	Byte	Printer type (00H=hardware I/O port, 01H=Model III, 02H=RS-232)
56C5H	Byte	Print activation flag (50H='P' when printing activated)
56F1H	Byte	Stop flag (C9H=RET when spooler stopped)
5C88H	Byte	Circular buffer enable flag (00H=disabled, 01H=enabled)
5DB4H	Byte	Interrupt driven printer flag (00H=disabled, 01H=enabled)

Buffer Pointers and Counters

Address	Type	Description
57FBH	Byte	Printer buffer read counter (F6H=empty, increments with each read)
57FDH	Byte	Keyboard buffer write counter (F6H=empty, increments with each write)
57E8H	Word	Keyboard buffer write position (unused/debugging)

Input Buffers

Address	Type	Description
5C44H	2 Bytes	Single character input buffer
5C46H	2 Bytes	Two-digit numeric input buffer
5C16H	26 Bytes	Filename input buffer

Baud Rate Table

Address	Type	Description
5DBCH-5DC3H	8 Bytes	Baud rate lookup table (22H, 44H, 55H, 66H, 77H, AAH, CCH, EEH)

Address	Original	Modified By	Purpose
550BH	E5 (PUSH HL)	5639H → C9H	Stop spooler by inserting RET to disable operation handler
5533H	3A3455 (LD A,(5534H))	-	Reads spool count for display/logic
5534H	Variable	55D9H, 55EFH	Current spool count - number of active spool files
5548H	00H	594CH → 00H/01H	Multi-line feed mode flag for soft form feed
554EH	Variable	5957H	Total lines per page for form feed boundary
5553H	Variable	593DH	Print lines per page (maximum line count)
5554H	C9H (RET)	5931H → C9H/D8H	Line overflow handler (C9H=ignore, D8H=check)
5599H	0053 (5300H)	55ACH, 5619H	Current buffer write pointer for output capture
55BBH	C4 (CALL NZ)	5963H → C4H/11H	ETX finalization call (C4H=enable, 11H=LD DE,nnnn to disable)
5639H	Writes C9H	-	Stop command modifies 550BH and 56F1H to RET
56C5H	00H	54ECH, 56CEH	Print activation flag (50H='P' activates printing)
56F1H	00H	5639H → C9H	Stop flag at 56F0H+1 (C9H stops spooler operation)
570EH	0000H	5C7BH	Saved disk buffer pointer from 4016H
5708H	0000H	5C72H	Saved keyboard break vector from 4026H
573DH	0000H	56C1H, 57C8H, 578DH	Current buffer read pointer for printing
5759H	00H (NOP)	5683H → C9H	Temporarily disable print routine (patchable location)
576DH	00H	5670H	Saved seconds value for timeout calculation
5777H	0000H	5677H	Saved minutes:hours for timeout calculation
577EH	00H	5991H	Timeout threshold in seconds
5792H	01H	5903H, 5907H, 5915H	Printer type configuration (00H/01H/02H)
57A4H	0000H	5C75H	RS-232 driver address for CALL at 57A3H
57BDH	18H (JR)	591FH → 18H/3EH	Printer port selection (18H=primary EAH, 3EH=alternate E8H)
57D5H	C9H (RET)	5972H → 00H/C9H	Line feed insertion (00H=NOP enables, C9H=RET disables)
57DDH	00H (NOP)	5C91H → C9H	Keyboard input check (C9H=RET disables monitoring)
57E3H	Varies	5C84H	Keyboard scan routine address (modified if interrupt mode disabled)
57FBH	F6H	5810H, 581AH	Buffer read counter (F6H=empty state)
5802H	4054H	580DH	Buffer read pointer in LD HL,nnnn at 5801H
5822H	31H ('1')	5988H, 5652H	Pool number digit in filename template
5C88H	01H	5C87H+1	Circular buffer flag (00H=disabled, 01H=enabled)
5DB4H	01H	5DB3H+1	Interrupt driven printer flag (00H=disabled, 01H=enabled)
5662H	Varies	5C8CH	Printer buffer check call address (modified if circular buffer disabled)

COMMAND PROCESSING - 5457H-5507H

Address	Description
5457H	Main Command Parser: Entry point that scans command line for P, S, C, W commands. Jumps to syntax error (4409H) if invalid. Calls 547DH to find last character before ENTER.
547DH	Get Last Character: Scans forward through command line to find last character before 0DH (ENTER). Returns character in A.
5486H	Status Display: Shows current spooler status including "SPOOL STATUS", printing status, spooling count, and pool backlog. Reads stop flag at 56F1H.
54C5H	Conditional Display Helper: Converts number to ASCII (+30H), stores at 5822H, calls DOS print routine if non-zero.
54D5H	Clear Command Handler: Prompts "CLEAR BACK LOG OR PRINT (B/P)?", waits for response, either clears pool table (B) or activates printing (P) by setting 56C5H.
54F2H	Buffer Clear Loop: Scans pool table at 5828H, sets active pools (status ≥02H) to 00H until FFH end marker.
5501H/5505H	Command Entry Points: Set C=03H (Write) or C=04H (Stop), fall through to common handler at 5507H.
5507H	Common Operation Handler: Pushes 402DH return address twice, preserves registers, calls 567DH screen handler then 5518H main logic. Address 550BH modified to C9H when stopping.

CORE SPOOLING OPERATIONS - 5518H-5650H

Address	Description
5518H	Main Spooler Logic: Checks DOS mode (4369H bit 6), dispatches C=04H to stop routine, C=03H to write operation. Displays "CAN'T SPOOL FROM DOS" if in DOS.
5533H	Write Operation: Checks spool count at 5534H, calls 55F7H if zero to initialize, loads screen position counter from 582EH.
553DH	ENTER Key Handler: Calls 557EH output routine, increments line feed counter, checks multi-line mode flag at 5548H, handles overflow at FFH.
5557H	Form Feed Handler: Processes 0CH character - either clears counter or calculates line feeds to form boundary using 554EH maximum, outputs via loop at 5571H.
557AH	ETX Check: Tests for 03H (End of Text), jumps to 55B9H finalization routine if found.
557EH	Character Output to Buffer: Writes character to buffer at 5599H (initially 5300H), increments pointer, checks for 5400H boundary. Handles 0DH by filling with spaces.
55A4H	Buffer Full Handler: Writes 256-byte buffer to disk via 443CH, displays "CAN'T WRITE TO" error on failure, calls 55F0H verification, resets pointer to 5300H.
55B9H	ETX Finalization: Writes final partial buffer if not empty, closes file via 4428H, counts active files in pool table starting at 5827H, updates spool count at 5534H.
55F0H	Write Verification: Calls 444BH verify routine, calls 55D0H close on error.
55F7H	Initialize New Session: Calls 5642H pool counter, displays "SPOOL FULL. WAITING ON PRINTER" if pool not empty, stores count, calls 5651H filename setup, resets buffer pointer, creates file via 4420H.
5634H	Stop Spooler: Stores C9H (RET opcode) at 550BH and 56F1H to disable operations, displays "SPOOL STOPPING." message.
5642H	Count Active Files: Scans pool table at 5828H, increments C counter for each non-zero status until 00H (empty) or FFH (end marker).
5651H	Filename Setup: Converts pool number to ASCII (+30H), stores at 5822H, copies 8 bytes from template at 581EH ("POOL_:1") to FCB at 5420H via LDIR.

PRINTER OUTPUT MANAGEMENT - 5661H-5790H

Address	Description
5661H	Printer Input Buffer Check: Calls 57FAH to check for available character, saves system clock state (4041H-4043H) at 576DH and 5777H if character available.
567DH	Screen Output Handler: Main coordinator - temporarily patches 5759H to C9H, calls 575AH, checks DOS mode (4369H bit 6), manages printer status flag at 5766H, coordinates pool file operations.
56F6H	Print Command Handler: Closes active spool file if present, installs printer driver vectors (4413H), adjusts memory limits (4026H, 4016H, 4049H), displays "SPOOL STOPPING." on error.
5739H	Buffer Pointer Comparison: Compares buffer write pointer against 5300H limit to check for overflow. Returns Z if equal, C if below, NC if above.
5745H	Clear FCB and Close File: Zeros extent field (FCB+8), record count fields (FCB+12, FCB+13), jumps to DOS close routine at 4428H.
575AH	Printer Output Main Entry: Preserves IX register, calls actual printer handler at 5762H.
5762H	Printer Character Output Handler: Calls keyboard input at 57DDH, checks printer active flag at 5766H, calculates elapsed time since last character (576DH, 5777H), validates buffer position, dispatches to output.
5791H	Physical Printer Dispatcher: Routes output based on printer type at 5792H: 00H→hardware I/O port (57B8H), 01H→Model III port (57AAH), 02H→RS-232 (5799H).
57AAH	Model III Printer Output: Verifies Model III compatibility (37E8H & F0H = 30H), outputs character to memory-mapped port at 37E8H.
57B8H	Hardware Printer Output: Checks printer ready via port EAH bit 6, handles alternate port E8H, outputs character to port EBH. Instruction at 57BDH modified to select port.
57DDH	Keyboard Input Check: Calls ROM keyboard scan at 03E3H, stores characters in circular buffer at 5440H, manages buffer counter at 57FDH, handles wraparound via 5817H.

BUFFER MANAGEMENT - 57FAH-5817H

Address	Description
57FAH	Read from Printer Input Buffer: Manages circular buffer reads from 5440H base. Checks counter at 57FBH (F6H=empty), returns character or 00H, calls 5817H on wraparound.
5817H	Reset Buffer Pointers: Resets circular buffer to start (5440H) and counter to F6H when buffer wraps.

CONFIGURATION AND INSTALLATION - 58FAH-5A54H

Address	Description
58FAH	Configuration Initialization: Comprehensive setup prompting for: existing driver (5A55H), parallel/serial (5A78H), H14 printer (5A9AH), pages mode (5AADH), form feed type (5ABAH), lines per page (5AD8H, 5AF6H), ETX handling (5B14H), line feed (5B36H), pool number (5B5AH), timeout (5B78H). Modifies code at 5792H, 57BDH, 5554H, 5548H, 554EH, 55BBH, 57D5H, 5824H, 577EH, 5DB4H, 5C88H.
5A2FH	Display Prompt and Get Character: Displays prompt string (terminated with 03H) via 4467H, reads one character into buffer at 5C44H via DOS input routine at 0040H.
5A3AH	Get Two-Digit Numeric Input: Prompts for 10-99 range input, validates 2 characters entered, calls ROM conversion at 0E6CH, returns value from 4121H.
5A18H	Yes/No Prompt Handler: Sets BC to 594EH (Y/N characters), falls through to two-option prompt handler.
5A1BH	Two-Option Prompt Handler: Generic handler for two-character choices. Loops until valid response matching B or C received. Returns Z if first option, NZ if second.
59B0H	Program Installation to Disk: Creates DUMP command at 5C11H with hex addresses, copies program data, formats filename, writes to disk via 4419H, displays "DONE" message.
59FDH	Convert Address to Hex String: Converts 16-bit address in DE to 4 ASCII hex characters at (HL). Calls 5A02H for high byte then low byte.
5A02H	Convert Byte to Hex Characters: Converts byte in A to two ASCII hex chars. Rotates high nibble to low position, calls 5A0BH twice.
5A0BH	Convert Nibble to Hex Character: Masks low 4 bits, adds 30H for '0'-'9' or adds 37H for 'A'-'F', stores at (HL) and increments.

ALTERNATIVE COMMANDS - 5C4BH-5C6DH

Address	Description
5C4BH	Alternative Command Entry: Calls 547DH to get last character. Tests for 'I' (49H) → jumps to 58FAH configuration. Tests for 'A' (41H) → continues to purge all. Otherwise generates syntax error.
5C58H	Purge All Pool Files: Iterates A=01H to 05H, calls 5651H to setup filename, opens file via 4424H, closes via 5745H if successful. Effectively purges all pool files.
5C6FH	Save System Vectors: Preserves keyboard break vector (4026H) at 5708H and 57A4H, disk buffer pointer (4016H) at 570EH. Applies interrupt and circular buffer configuration based on flags at 5DB4H and 5C88H.

HARDWARE INITIALIZATION - 5C94H-5CB1H

Address	Description
5C94H	Hardware Printer Port Initialization: Tests printer type at 5792H. If 00H (hardware port), configures expansion interface: outputs 00H to E8H, reads E9H, masks with F8H, ORs with 04H, outputs to EAH. Reads baud rate from table at 5DBCH indexed by E9H bits 0-2, outputs to E9H.

RELOCATION AND INSTALLATION - 5CB2H-5DD0H

Address	Description
5CB2H	Calculate Relocation: Loads HIGH$ from 4049H, subtracts program size (06FAH) to get new base address. Copies program in two blocks: header (5450H, 0CH bytes to base+0251H) and main code (049EH bytes). Calculates relocation offset (destination - source).
5CE0H	Address Relocation Scanner: Sophisticated instruction analyzer that scans copied code from start to end (BC). For each byte: detects instruction type and length via opcode analysis (handles 00-3F, 40-BF, C0-FF ranges), identifies 3-byte instructions with address operands (01H, 11H, 21H, 31H, C3H, CDH, C4H/CCH/D4H/DCH/E4H/ECH/F4H/FCH), extracts 16-bit addresses, checks if address is within spooler range (5200H-58F9H), adds relocation offset if in range, writes back relocated address. Special handling for: ED prefix (LD (nnnn),rr at 43H), DD/FD prefixes (indexed instructions), CB prefix (bit instructions), I/O instructions (D3H, DBH). Advances pointer appropriately for each instruction type.
5D82H	Installation Completion: Verifies relocation successful (generates error 3AH if not). Displays "SPOOL ACTIVE" message at 5DC4H. Installs program via 4461H at relocated address. Updates HIGH$ at 4049H to protect spooler. Calculates and stores relocated vectors: 550BH+offset → 4026H (break handler), 5661H+offset → 4016H (buffer check), 5755H+offset → DE (vector table). Conditionally calls 4410H to install printer driver if flag at 5DB4H set. Returns to DOS via 402DH.

Filename:	POOL_:n where n = 1-5 (pool number)
Drive:	Drive specified in configuration (0-3)
Contents:	Raw printer output data captured from applications
Structure:	256-byte records written sequentially Printable characters (≥20H) stored directly Control characters processed: 0DH (carriage return), 0CH (form feed), 03H (ETX end marker) Final partial record written on file close No header or trailer - pure data stream
Pool Table Status:	00H = Empty pool slot 01H-FEH = Number of files queued in pool FFH = End of table marker

Self-Relocation Technique:

ASPOO implements a sophisticated self-relocation algorithm that scans through copied code and adjusts all absolute addresses. The scanner at 5CE0H analyzes each instruction's opcode to determine length and whether it contains a 16-bit address operand. For 3-byte instructions (LD rr,nnnn, JP nnnn, CALL nnnn), it extracts the address, checks if it falls within the spooler's original range (5200H-58F9H), and if so, adds the relocation offset. This allows the spooler to be positioned anywhere in memory below HIGH$ without requiring reassembly.

Self-Modifying Code Strategy:

The program extensively uses self-modifying code for configuration. Rather than using variables and conditional branches, configuration settings directly modify instruction opcodes and operands. For example, the stop flag at 56F1H changes a PUSH HL to RET (C9H), completely bypassing the spooler logic. This technique was common in the era due to memory constraints and provides faster execution than conditional branches.

DOS Vector Interception:

ASPOO integrates with NEWDOS/80 by hijacking system vectors. The keyboard break vector (4026H) is redirected to the spooler's return routine, allowing it to maintain control. The disk buffer pointer (4016H) is redirected to the printer buffer check, intercepting all printer I/O. This transparent interception means applications continue using normal printer output without modification.

Memory Protection:

After relocation, ASPOO adjusts the HIGH$ system variable (4049H) to point just below the relocated spooler code. This prevents BASIC programs and DOS operations from overwriting the spooler. The spooler calculates its new position as HIGH$ - 06FAH (program size), ensuring it always resides at the top of available memory.

Buffer Management:

The spooler uses three buffers: (1) Output buffer at 5300H-5400H captures printer data from applications, written in 256-byte blocks when full. (2) Input buffer at 5200H-5300H reads spool files for printing. (3) Keyboard buffer at 5440H-5540H monitors user input during printing, using circular buffer technique with wraparound at F6H initial counter value.

Timeout Detection:

The printer delay mechanism at 5762H saves system clock values (seconds at 4041H, minutes:hours at 4042H-4043H) when characters arrive. Before printing each character, it calculates elapsed time and compares against the configured threshold. This prevents premature printing while the application is still generating output, only starting after the configured idle period.

Hardware Abstraction:

ASPOO supports three printer interfaces through runtime configuration: (1) RS-232 serial via driver calls at 57A4H, (2) Model III memory-mapped port at 37E8H, (3) Model I expansion interface I/O ports at E8H/E9H/EAH/EBH. The dispatcher at 5791H routes output based on the printer type byte at 5792H, providing hardware independence.

5450H - Program Header and Identification

This section contains the program identification string "ASP" (Apparat Spooler) padded with NOPs. The program entry point begins at 545BH.

5457H - Main Entry Point and Command Parser

Program entry point that parses the command line for spooler commands. Recognizes commands: P (Print), S (Stop), C (Clear), W (Write buffer to disk). Invalid commands result in a Syntax Error at 4409H. Entry: HL points to command line buffer. Exit: Jumps to appropriate command handler or returns via 402DH.

547DH - Get Last Character Before ENTER

Subroutine that advances through the command line buffer to find the last character before the carriage return (ENTER). This allows parsing command modifiers that follow the main command. Entry: HL points to current position in command buffer. Exit: A contains last character before ENTER, HL points to that character.

5486H - Display Spool Status

Displays the current status of the spooler when no command is specified. Shows "SPOOL STATUS", whether output is currently being printed, number of files spooling, and backlog count. Entry: Called when ENTER is pressed without a command. Exit: Returns to DOS via 402DH.

54C5H - Display Number with Message

Conditionally displays a message with a numeric value. If the value in Register A is zero, returns immediately without displaying. Otherwise, converts the number to ASCII and displays the message. Entry: A contains numeric value to display, HL points to message string. Exit: Message displayed if A was non-zero.

54D5H - Clear Backlog Command Handler

Handles the 'C' (Clear) command which prompts the user to either clear the backlog or print it. Displays prompt and waits for 'B' (backlog clear) or 'P' (print) response. Entry: Called from command parser when 'C' command detected. Exit: Either clears buffer (returns via 402DH) or continues printing (jumps to 56C5H).

5501H - Write Buffer Command Entry

Entry point for the 'W' (Write) command which writes spooler buffer to disk. Sets up operation code and falls through to common spool operation handler. Entry: Called from command parser when 'W' command detected. Exit: Continues to shared spool operation code at 5507H.

5505H - Stop Spooler Command Entry

Entry point for the 'S' (Stop) command which stops the spooler. Sets up operation code and continues to shared handler. Entry: Called from command parser when 'S' command detected. Exit: Falls through to shared code at 5507H.

5507H - Common Spool Operation Handler

Common handler for spool operations (Write and Stop). Sets up return address stack, preserves registers, and calls main spooler logic. Entry: C contains operation code (03H=Write, 04H=Stop). Exit: Returns to DOS via 402DH after operation completes.

5518H - Main Spooler Operation Logic

Main logic routine for spooler operations. Checks DOS mode, handles operation code dispatching for Write (C=03H) and Stop (C=04H) commands. Entry: C contains operation code (03H=Write, 04H=Stop), E=00H initially. Exit: Operation completed, returns to caller.

557EH - Output Character to Spool Buffer

Outputs a character to the memory-based spool buffer at 5300H-5400H range. Handles screen position tracking and buffer wrapping. When buffer fills, writes to disk. Entry: A contains character to output. Exit: Character written to buffer, buffer pointer advanced.

55B9H - Finalize Spool Buffer (ETX Handler)

Handles End of Text (ETX, 03H) character to finalize the current spool buffer. Fills remaining buffer with ETX markers and writes final buffer to disk. Updates pool counters to reflect completed spool file. Entry: A=03H (ETX), HL points to screen position. Exit: Buffer finalized and written, pool status updated.

55F0H - Buffer Write Verification and Management

Verifies disk write operations and manages buffer state after writes. Checks for write completion, handles printer wait conditions if buffer is full. Entry: Called after writing buffer to disk. Exit: C FLAG clear on success, set on error.

55F7H - Initialize New Spool Session

Initializes a new spooler session when first starting to spool output. Creates new spool file, displays "waiting on printer" message if needed, and sets up buffer pointers. Entry: C contains operation code, no files currently spooling. Exit: Spool file opened and ready, buffer initialized.

5634H - Stop Spooler Command Handler

Handles the 'S' (Stop) command to shut down the spooler. Patches the spooler entry points with RET instructions to disable spooling, displays stopping message. Entry: Called from command dispatcher when C=04H (Stop command). Exit: Spooler disabled, message displayed, returns to DOS.

5642H - Count Active Spool Files

Counts the number of active spool files in the pool table. Scans pool status bytes from 5828H onwards until finding FFH end marker. Entry: None. Exit: C contains count of active files (01H-FEH range), Z FLAG set if count=0, NZ FLAG set if count>0, A contains incremented final value.

5651H - Setup Pool Filename in FCB

Creates the spool filename "POOL_:n" in the File Control Block (FCB) at 5420H. Converts the pool number to ASCII and embeds it in the template string. Entry: A contains pool number (1-9), DE points to FCB at 5420H. Exit: FCB filename field populated with "POOL_:n" where n is the pool number.

5661H - Printer Input Buffer Check

Checks for available character from printer input buffer. Saves system state (clock values) if character available. Entry: None. Exit: A contains character if available (NZ), or 00H if buffer empty (Z). System clock state saved if character read.

567DH - Screen Output Handler and Printer Management

Main screen output handler that manages printer output for applications. Checks DOS mode, printer status flags, and coordinates output to physical printer or screen. Calls print buffer processor and manages pool file operations. Entry: None. Exit: Registers preserved, output processed.

56F6H - Print Command Handler

Handles the 'P' (Print) command to activate printer output from spool files. Closes any active spool file, sets up printer driver vectors, adjusts memory limits, and starts printing. Entry: Called from command parser when 'P' command detected. Exit: Printer activated and started, returns to DOS.

5739H - Buffer Pointer Comparison

Compares buffer write pointer against buffer limit to check for overflow. Entry: BC and HL contain pointers to compare. Exit: Z FLAG set if pointers equal (buffer at limit), C FLAG set if buffer full, NC FLAG if space available.

5745H - Clear FCB Fields and Close File

Clears specific fields in the File Control Block and closes the file. Zeros out extent and record count fields in the FCB. Entry: DE points to FCB. Exit: FCB fields cleared, file closed via DOS.

5755H - Printer Driver Vector Table

Data table containing printer driver configuration bytes. Used by DOS vector installation routine to configure printer I/O vectors.

575AH - Printer Output Main Entry

Main entry point for printer output processing. Preserves IX register and calls actual printer handler. Entry: Called by DOS when output sent to printer device. Exit: Character processed, IX preserved.

5762H - Printer Character Output Handler

Processes characters for printer output. Calls keyboard input routine to get character from buffer, checks timeout against saved clock values, validates buffer position, and dispatches to appropriate output handler based on system configuration. Entry: Character available in buffer or timeout check needed. Exit: Character output to physical printer or error returned.

5791H - Physical Printer Output Dispatcher

Dispatches character output to appropriate physical printer interface based on system configuration. Checks configuration flags and routes to RS-232, Model III printer port, or hardware printer port. Entry: C contains character to output. Exit: Character sent to printer, buffer pointer advanced.

57AAH - Model III Printer Port Output

Outputs character to TRS-80 Model III printer port. Checks printer compatibility and sends character directly to hardware. Entry: C contains character to output. Exit: Character sent to Model III printer port or error returned.

57B8H - Hardware Printer Port Output

Outputs character to hardware printer port via I/O ports. Checks printer ready status and sends character when ready. Handles both Model I expansion interface (port EAH) and alternate interface (port E8H). Entry: C contains character to output. Exit: Character sent to hardware printer port.

57D6H - Line Feed Insertion (Unused)

Appears to be unused code for inserting line feed (0AH) before carriage return. This routine is not called in normal execution flow. Entry: HL points to buffer position. Exit: 0AH inserted, buffer pointer updated.

57DDH - Keyboard Input Check During Print

Checks for keyboard input during printer operations. Uses ROM keyboard scanning routine and manages circular input buffer at 5440H. Handles buffer wrapping when full. Entry: None. Exit: A contains character if available (NZ), or 00H if no input (Z).

57FAH - Read Character from Printer Input Buffer

Reads next character from the circular printer input buffer at 5440H. Manages buffer read pointer and handles wraparound. Entry: None. Exit: A contains character from buffer (NZ) or 00H if buffer empty (Z). HL and BC preserved.

5817H - Reset Buffer Pointers

Resets circular buffer pointers to start position when buffer wraps. Entry: Called when buffer counter wraps to 00H. Exit: HL points to buffer start, A contains reset counter value.

581DH - Data Area and Message Strings

Program data area containing message strings for display, spool status table, and working variables. Includes pool filename templates, status messages, and configuration data.

58FAH - Configuration Initialization Entry Point

Main initialization routine that prompts user for spooler configuration settings. Configures printer type, form feed handling, line counts, and other operational parameters through interactive prompts. Entry: Called during program installation. Exit: Configuration complete, returns to DOS via 402DH.

59B0H - Program Installation to Disk

Writes configured spooler program to disk with embedded configuration. Creates three copies of program data at different memory locations, then writes to disk file. Entry: Configuration complete. Exit: Program written to disk, returns to DOS.

59FDH - Convert Address to Hex String

Converts 16-bit address in DE to ASCII hexadecimal string at (HL). Processes high byte then low byte. Entry: DE contains address to convert, HL points to output buffer. Exit: 4-character hex string written to (HL), HL advanced past string.

5A02H - Convert Byte to Hex Characters

Converts byte in A to two ASCII hexadecimal characters at (HL). Processes high nibble then low nibble. Entry: A contains byte to convert, HL points to output buffer. Exit: Two hex characters written, HL advanced by 2.

5A0BH - Convert Nibble to Hex Character

Converts low nibble of A to ASCII hexadecimal character. Handles 0-9 as '0'-'9', A-F as 'A'-'F'. Entry: A contains nibble in low 4 bits, HL points to output location. Exit: ASCII hex character stored at (HL), HL incremented.

5A18H - Yes/No Prompt Handler

Displays prompt and waits for Y or N response. Returns with Z FLAG set for 'N', NZ FLAG set for 'Y'. Continues prompting until valid response received. Entry: HL points to prompt string. Exit: Z FLAG indicates response (Z='N', NZ='Y'), BC contains response characters.

5A1BH - Two-Option Prompt Handler

Generic prompt handler for two-character choices (P/S, S/H, etc.). Displays prompt and waits for response matching either character in BC. Returns with Z FLAG set if first option selected. Entry: HL points to prompt string, B contains first option character, C contains second option character. Exit: Z FLAG set if B matched, NZ FLAG set if C matched.

5A2FH - Display Prompt and Get Single Character

Displays a prompt string and reads one character from the keyboard. Used by configuration routines for single-character responses. Entry: HL points to prompt string (terminated with 03H). Exit: Character read into buffer at 5C44H, HL updated.

5A3AH - Get Two-Digit Numeric Input (10-99)

Prompts for and validates two-digit numeric input in range 10-99. Continues prompting until valid input received. Entry: HL points to prompt string. Exit: A contains validated numeric value (10-99 decimal).

5A55H - Configuration Prompt Strings

Data area containing all configuration prompt strings used during spooler installation. Each string is terminated with 03H byte (ETX). Strings are displayed to guide user through configuration process.

5C11H - DUMP Command Template String

Template for DUMP command used to write configured program to disk. Contains placeholder addresses that are filled in by hex conversion routines during installation. Command format: "DUMP device/filename startaddr endaddr entryaddr".

5C44H - Input Buffer Area

Working buffer space for keyboard input during configuration. Single character responses stored at 5C44H, two-character responses at 5C46H.

5C4BH - Alternative Command Entry Point

Alternative entry point for ASP command processing. Handles 'I' command for installation/configuration and 'A' command for purging all pool files. Entry: HL points to command line. Exit: Command processed or error generated.

5C58H - Purge All Pool Files Command Handler

Handles the 'A' (purge All) command to delete all pool files (POOL_:1 through POOL_:5). Iterates through each pool number, opens and closes each file to clear it. Entry: Called from 5C55H when 'A' command detected. Exit: All pool files purged, returns to main command handler.

5C6FH - Save System Vectors and Configuration

Saves NEWDOS/80 system vectors and applies configuration settings. Stores keyboard break vector, disk buffer pointer, and configures interrupt/buffer options based on installation settings. Entry: All pools purged. Exit: System vectors saved to self-modifying code locations.

5C94H - Hardware Printer Port Initialization

Initializes hardware printer port if using I/O port printer (not RS-232 or Model III). Configures expansion interface ports E8H/E9H/EAH for printer communication. Looks up baud rate from configuration table. Entry: Configuration loaded. Exit: Printer port initialized if needed.

5CB2H - Calculate Relocation and Copy Program

Calculates new memory location for spooler program, copies program data to new location with address relocation, and installs program at calculated address. Adjusts HIGH$ memory limit, copies code blocks, relocates addresses in copied code. Entry: Configuration complete. Exit: Program relocated and installed, ready for operation.

5CE0H - Address Relocation Scanner

Scans through copied code and relocates all absolute addresses that point to spooler code area. Identifies instructions with 16-bit address operands, checks if addresses fall within spooler range (5200H-58F9H), and adjusts them by relocation offset. Entry: HL points to start of code, BC points to end, relocation offset on stack. Exit: All addresses relocated, spooler ready for execution.

5D82H - Installation Completion

Completes spooler installation after relocation. Verifies relocation successful, displays "SPOOL ACTIVE" message, updates system vectors to point to relocated code, adjusts HIGH$ memory limit, and initializes printer driver. Entry: Relocation complete, offset and addresses on stack. Exit: Spooler installed and active, returns to DOS.

5DBCH - Baud Rate Lookup Table

Lookup table for printer baud rate configuration values. Indexed by baud rate setting from expansion interface port E9H (bits 0-2). Table contains port configuration values for different baud rates.

5DC4H - Final Message String

Completion message displayed when spooler is successfully installed and activated.

End of Program

Program Entry Point: 5C4BH - Alternative command entry for 'I' (Install) and 'A' (purge All) commands.