TRS-80 DOS - NEWDOS/80 v2.0 for the Model I - SYS11/SYS Disassembled

SYS11/SYS

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SYS11 implements the BASIC RENUM (Renumber) command for NEWDOS/80 v2.0. This utility renumbers BASIC program lines and automatically updates all line number references in GOTO, GOSUB, ON...GOTO, ON...GOSUB, and similar statements. The command operates in two phases: Phase 1 scans the program building a table of old-to-new line number mappings, and Phase 2 performs the actual renumbering by updating all references throughout the program.

RENUM syntax: RENUM [new][,old[,increment]] where new is the starting line number for renumbering (default 10), old is the first line to begin renumbering from (default is start of program), and increment is the step between line numbers (default 10).

Address	Bytes	Purpose
4D04H-4D05H	2	Starting old line number (RENUM from)
4D06H-4D07H	2	Ending old line number (RENUM to)
4D08H-4D09H	2	Maximum new line number limit
4D0AH	1	Flag: Non-zero if RENUM range specified
4D0BH	1	Flag: Non-zero if checking line bounds
4D4CH-4D4DH	2	Self-modifying: Line table pointer (scan address)
4DEDH-4DEEH	2	Current line number being parsed
4DE4H	1	Flag: DATA/REM skip mode
4E81H	1	Flag: Statement type indicator
4E8AH-4EC1H	56	Token dispatch table (token, handler address pairs)
4EF6H-4EF7H	2	Current BASIC program scan pointer
4F01H-4F02H	2	Current line start address
4FA6H	1	Bit flags: Bit 0 = first error displayed
5014H-5015H	2	Starting line address in program
5035H-5036H	2	Program expansion offset
50C0H-50C1H	2	Ending line number (high)
50C8H-50C9H	2	Last line address found
50F2H-50F3H	2	Program size adjustment
50F7H-50F8H	2	Available memory remaining
5121H	1	Phase flag: 0=Phase 1 (build table), 1=Phase 2 (renumber)
515AH-515BH	2	Line number difference (new - old)
515EH-515FH	2	Line count for current number parse
5168H-5169H	2	Memory expansion required
5170H-518BH	28	Error message: "FATAL ERROR. TEXT NOW BAD"
518CH-5197H	12	Error message: "ERROR LINES"
5198H-519CH	5	Completion message: "DONE"
51A2H-51F3H	82	Reserved/NOP area (workspace)
64CAH-654AH	128	Line number mapping table (64 entries × 2 bytes)

Address	Purpose
4D0CH	Entry point / store line number mapping
4D25H	Phase 1 initialization
4D6AH	Parse line content for tokens
4DADH	Token dispatch loop
4E4CH	Parse decimal line number (0-65529)
4E8AH	Token dispatch table
4EC3H	Binary search line lookup in mapping table
4F54H	Display error with line number
4F97H	Phase 1 complete / start Phase 2
4FFDH	Phase 2 complete
5050H	Fix next-line pointers after memory move
5063H	Print "DONE" and return to BASIC
5120H	Get next byte from program (phase-aware)
5147H	Print message string

Address	Set By	Purpose
4D4CH	4D65H, 4FEAH	Line table pointer (in LD HL,nnnn)
4DEDH	4D78H	Current line number (in LD DE,nnnn)
4DE4H	4DA8H	DATA/REM skip flag (in LD A,nn)
4E81H	4DA4H, 4DD1H	Statement type flag (in OR nn)
4EF6H	4D34H, 5007H	Scan pointer BC storage
4F01H	4D38H	Current line start (in LD HL,nnnn)
4FA6H	4F65H	Error display flag (bit 0 = first shown)
5014H	507BH	Starting line address
5035H	50CAH	Program expansion offset
50C0H	5087H	Ending line number (in LD DE,nnnn)
50C8H	50AFH	Last line address (in LD DE,nnnn)
50F2H	50CDH	Program size adjustment (in LD DE,nnnn)
50F7H	5117H	Remaining memory (in LD DE,nnnn)
5121H	4FDBH	Phase flag: 0=Phase 1, non-zero=Phase 2
515AH	5163H	Line number difference storage
515EH	4E73H	Digit count storage (in LD DE,nnnn)
5168H	516CH	Memory expansion needed (in LD DE,nnnn)

Token	Handler	Meaning
00H	4D34H	End of line - process next line
22H	4D85H	Quote - skip quoted string
3AH	4DA3H	Colon - start new statement
88H	4D9AH	DATA - skip to end of statement
8DH	4DD9H	FOR - check for line numbers
8EH	4DD9H	NEXT - check for line numbers
91H	4D7EH	REM - skip to end of line
93H	4DD4H	(token) - parse line number
95H	4DC5H	(token) - check skip mode
9EH	4DCFH	RESTORE - parse line number
9FH	4DC1H	(token) - set skip mode
A1H	4E23H	RESUME - handle parentheses
A4H	4E23H	ON - ON...GOTO/GOSUB handling
A5H	4E12H	ON variant - same handling
B4H	4E12H	ERL - error line handling
B5H	4E03H	ELSE - check for line number
C2H	4DD4H	AUTO - parse line number
CAH	4DADH	DELETE - dispatch
FFH	(end)	End of table marker

4D0CH - Entry Point / Store Line Number Mapping

This routine is called to store a line number mapping entry in the translation table. On entry, DE contains the old line number, BC contains the new line number, and HL points to the current position in the mapping table. The table stores pairs of (old, new) line numbers for Phase 2 reference lookup.

4D25H - Phase 1 Initialization

Initialize for Phase 1 scanning. This sets up the program scan from the beginning and prepares to build the line number mapping table. Phase 1 scans through the BASIC program identifying which lines will be renumbered and what their new numbers will be.

4D6AH - Parse Line Content

Skip past the line header (next line pointer and line number) and begin parsing the line content for tokens that reference line numbers (GOTO, GOSUB, etc.).

4D7EH - Skip to End of Line

Called when we need to skip to the end of the current BASIC line (e.g., after processing a REM or DATA statement).

4D85H - Handle Quoted Strings

When a quote character (22H) is encountered in the BASIC line, this routine skips past the entire quoted string since line numbers inside strings should not be renumbered.

4D95H - Check for Quote or Colon

Part of the main parsing loop. This checks if the current character is a quote (start of string literal) or a colon (statement separator). Strings must be skipped entirely, and colons signal the start of a new statement.

4DA3H - Begin Statement Scan

Reset statement flags and begin scanning a new BASIC statement. This is entered after processing each statement separator (colon) or at the start of a line. The flags track whether we're in a DATA/REM statement and the statement type.

4DC1H - Set DATA/REM Skip Mode

Called when a DATA or REM token is encountered. Sets a flag that causes subsequent bytes to be skipped until end of line, since DATA constants and REM comments should not have their contents parsed for line numbers.

4DC5H - Check Skip Mode Active

Check if DATA/REM skip mode is active. If so, all bytes are ignored until end of line.

4DCFH - Handle GOTO/GOSUB Tokens

Called when GOTO (token CEH) or GOSUB (token CDH) is encountered. These statements require line number arguments that must be renumbered. This routine parses the line number and records it for potential update.

4DF9H - Line Number Overflow Error Handler

Called when a line number exceeds the maximum valid value (65529). Displays error and aborts operation.

4E00H - Handle THEN Token

Handle the THEN token (D2H). THEN can be followed by a line number (for implied GOTO) or by statements. This checks if a digit follows.

4E12H - Handle ON Token

Handle the ON token (A4H/A5H). ON...GOTO and ON...GOSUB statements have lists of line numbers that need renumbering. This scans for the GOTO or GOSUB token that follows the numeric expression.

4E23H - Handle Function with Parentheses

Handle tokens that can have parenthesized arguments containing commas. This tracks parenthesis nesting so that commas inside parentheses are not mistaken for ON...GOTO/GOSUB separators.

4E40H - Get Next Byte with End Check

Get next byte from the BASIC line, but check for end of line or statement separator. If either is found, pop return address and go to next statement.

4E4CH - Parse Line Number

Parse a decimal line number from the BASIC program text. Converts ASCII digits to binary and validates the result is within range (0-65529). Returns the line number in DE. If in Phase 2, also looks up the new line number from the mapping table.

4E8AH - Token Dispatch Table

This table maps BASIC tokens to handler addresses. Format: handler_low, handler_high, token. Searched linearly until token matches or FFH end marker.

4EC3H - Binary Search Line Lookup

Binary search through the line mapping table at 64CAH to find a line number. Returns pointer to the line in BASIC program. Table has 64 two-byte entries (128 bytes total).

4F22H - Lookup Old Line Number

Called when a non-zero line number was parsed. Looks up the old line number in the mapping table to find its new value.

4F54H - Display Error with Line Number

Display an error message with the offending line number. A = error code character, DE = line number.

4F97H - Phase 1 Complete / Start Phase 2

Called when Phase 1 scan reaches end of program. Checks if memory expansion is needed, expands program if necessary, then starts Phase 2 to actually update line numbers.

4FFDH - Phase 2 Complete

Called when Phase 2 finishes. Skip past line header bytes, update string boundary, then compact the program back down.

5050H - Fix Line Pointers

After moving program in memory, fix all the next-line pointers throughout the program.

5063H - Print Done Message

Print "DONE" message and return to BASIC.

5073H - Calculate Line Ranges

Calculate the starting and ending line addresses for the renumber operation based on user-specified range.

50EDH - Out of Memory Error

Called when there isn't enough memory to expand the program for renumbering.

50F1H - Calculate Memory Adjustment (Shrink Path)

Calculate how much memory needs to be adjusted. Entry with DE=0 for shrinking path.

50F6H - Calculate Memory Adjustment (Expand Path)

Calculate memory adjustment with stored offset value for expansion.

511DH - Skip Whitespace

Skip any whitespace characters (spaces, tabs) and return the next significant byte in A.

5120H - Get Next Byte from Program

Fetch the next byte from the BASIC program being scanned. Updates scan position and optionally copies byte to output buffer. Self-modifying code controls copy behavior.

512BH - Skip Whitespace Loop

Loop entry for whitespace skipping. Continues fetching bytes until non-whitespace found.

513BH - Check for Digit

Check if current byte is a decimal digit (0-9). Returns with carry set if digit found.

5147H - Print Message String

Print a null-terminated or 03H-terminated message string pointed to by HL.

5153H - Phase 1: Calculate Memory Expansion

During Phase 1, calculate how much memory expansion is needed based on the difference between old and new line number digit counts.

5170H - Error Message: "FATAL ERROR. TEXT NOW BAD"

ASCII message displayed when a fatal error occurs during Phase 2 renumbering.

518CH - Error Message: "ERROR LINES"

ASCII message header displayed before listing lines with errors.

5198H - Completion Message: "DONE"

ASCII message displayed when renumbering completes successfully.

519DH - Additional Range Validation

Perform additional validation of the renumber range parameters.

51A2H - Reserved/Workspace Area

Reserved area filled with NOPs (00H bytes). May be used as workspace during renumbering operations or reserved for future expansion. Extends from 51A2H to 51F3H (82 bytes).