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ML Variables

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Programming Features - ML Variables

The ML Variables provide an interface between BASIC and the internal Color 64 machine language environment. They allow BASIC programs to read system status information and control various aspects of BBS operation.

All ML variables begin with an exclamation point (!) followed by two digits (for example, !04). They may be used in numeric expressions just like BASIC variables.

Values are assigned using the format:

!XX,value

This syntax is similar to the BASIC POKE command. All ML variables accept values in the range 0–255. Attempting to assign a value outside this range will generate an error.

Some ML variables are read-only, as indicated in the table below. Others are structured as multi-element variables and are accessed using array-style indexing (for example, !23(0)). An out-of-range index will generate an error.

Example:

1000 !04,0:.01:!04,13:if!40<5then1000

In this example:

  • !04 is set to 0, changing the disk input end-of-line character.
  • .01 reads a line from disk.
  • !04 is restored to 13 (carriage return).
  • !40 (number of characters read) is tested. If fewer than 5 characters were read, the loop repeats.

All ML variable references invoke ML processing at address $4E21.

The table below summarizes the ML Variables:

ML Variable Summary
Var Description
!00 Carrier detect mode

If less than 128, carrier timeout is enabled. If 128 or greater, carrier timeout is disabled. See !11.

!01 Status variable (Read-Only)

Status after input commands (.00, .02, @8). 0 = OK 1 = Aborted (CTRL/P) 3 = Pause (CTRL/S) 4 = Aborted (CTRL/X) 255 = Carrier lost

!02 General input/output character

Holds character returned by .00 or .07. Otherwise contains undefined data.

!03 Maximum column for word wrap

When input exceeds this column and word wrap mode is enabled, wrapping occurs. Wrapped word (up to 15 characters) is buffered and reinserted at next input.

!04 End-of-line character

The .01 command or the @5 function will read in a line of data until this character is reached, unless the maximum line length is reached, or !15 is set. See also .01 and !15

!05 Translation mode

0 = ASCII translation 1 = Graphics mode (Commodore/ANSI) 2 = Simulated ASCII (graphics input restricted) See also !18.

!06 Uppercase input constraint

If non-zero, alphabetic input (.02 or @8) is forced to uppercase.

!07 Word wrap mode

If non-zero, word wrap is enabled. See !03.

!08 Wrap/Width Threshold

See Undocumented features: !8.

!09 Character output mask

If not 0, this character will be printed instead of what is typed when inputting a line (the .02 command or the @8 function). This is used when the password is entered (asterisks are printed).

!10 Line feed mode

Active only in ASCII translation mode. If non-zero, ASCII 10 follows ASCII 13. See !05.

!11 Carrier timeout flag

0 = Timer suspended 1 = Timer active (counts to 255 if no carrier) Carrier is checked at 1/60 second intervals (~4.25 seconds timeout). Will hold value of 255 if timed out.

!12 Local mode

1 = disables modem I/O (local mode - no information is outputted to modem) 0 = enables modem I/O.

!13 Inactivity timeout flag

Non-zero value indicates inactivity timeout has occurred (~2 minutes of inactivity).

!14 Disk input file number

Used by .01, @5, .12 and other disk routines.

!15 End-of-line override mode

If non-zero, then the disk input routine will ignore the !04 end of line character and will fill the input buffer until the end of the file is reached, or until the maximum number of characters (length of TX$) has been reached.

!16 SEQ file abort disable

If non-zero, then the next sequential file read (with the .12 command) cannot be aborted by either the spacebar or CTRL/P keys. Resets to zero after completion of file read.

!17 Pager line count

0 disables pager. Non-zero sets pause interval (lines) during .12 sequential reads.

!18 ANSI mode

Active only in Graphics translation mode. If non-zero, ANSI translation is enabled. See !05.

!19 MCI disable flag

If non-zero, MCI processing is disabled for one output line. Automatically resets after output.

!20 Caller log buffer status (Read-Only)

0 = Empty 1 = Contains data >1 = Full (requires disk write)

!21 Variable Stack Number (Read-Only)

Current .18 stack level. 0 if no active stacks.

!22 Network transfer timeout

Set to 128 + minutes when network file transfer initiated (starts timer). 0 disables timer. Transfer aborts if timer expires.

!23 Non-SwiftLink BPS timer table

Table of 18 bytes; holds the timer values used by the Non-SwiftLink systems when sending and receiving the individual bits of data.

  • There are 6 bytes for each BPS rate (300, 1200, and 2400 respectively),
  • For each of the 6 bytes there are 2 bytes for the output bit time, input bit time, and half-bit time
  • Each of the two bytes is a 16-bit value arranged in low byte, high byte order.

The table is as follows: 300 BPS output bit time, 300 BPS input bit time, 300 BPS half-bit time, 1200 BPS output bit time, etc. To access any individual byte of the table, just index !23 like an array (i.e. !23(0) would be byte 0 of the table).

!24 Carrier type

Hardware comparison value for carrier detection (set by Setup).

!25 Carrier status (Read-Only)

Non-zero if carrier detected.

!26 SwiftLink flag (Read-Only)

0 = Non-SwiftLink 1 = SwiftLink system

!27 Term buffer mode

If this is not zero, then all characters printed to the screen will also be put into the term buffer. • Parameters of the buffers are established by the !28, !29, and !30 variables. • Output is diverted to file number 3 (normally screen output). • Used by the Plusterm program.

!28 Term buffer pointer

This is a 16-bit address in low byte, high byte format which points to the next open character in the term buffer. • !28(0) is the low byte, and !28(1) is the high byte. • Used by the Plusterm program.

!29 Term buffer bottom pointer

16-bit address of first byte of buffer. Used by the Plusterm program.

!30 Term buffer top pointer

16-bit address of last valid byte. Used by the Plusterm program.

!31 Current BPS rate (Read-Only)

0=300, 1=1200, 2=2400, 3=4800, 4=9600, 5=14400, 6=19200, 7=38400

!32 Modem Input buffer empty flag (Read-Only)

0 = Empty Non-zero = Characters pending

!33 X-Modem ASCII conversion mode

If non-zero, converts ASCII to PETSCII during transfer.

!34 X-Modem CRC retry count

Sets the number of times that the system will attempt to engage CRC (Cyclical Redundancy Check) at the beginning of an X-Modem file transfer.

!35 Punter block size

Sets the Block size in bytes for Punter protocol.

!36 Transfer file type

1 or 3 = PRG 2 = SEQ

!37 Current protocol (Read-Only)

0 = Punter 1 = X-Modem

!38 Transfer timeout flag

Non-zero after transfer complete indicates carrier or network timeout during transfer.

!39 Transfer abort status

Non-zero indicates aborted transfer.

!40 Input character count

For keyboard input (.02 or @8) or disk input (.01 or @5), this value is the number of characters read in during input.

!41 Alternate output mode

If non-zero, BBS output is diverted to file #3.

  • Affects BBS output only (BASIC PRINT commands unaffected).
!42 Day of month (Read-Only)

Updated by @16 function.

!43 Month of year (Read-Only)

Updated by @16 function.

!44 AM/PM flag (Read-Only)

0 = AM Non-zero = PM

!45 Current hour (Read-Only)

Holds values 1–12, updated by @11.

!46 Scratch register

General-purpose read/write variable. See Undocumented features: !46.

!47 Character output delay

May be used to slow output of the system for slower systems. 0 = No delay 255 = Maximum delay

!48 Fast garbage collect mode

If non-zero, enables fast string garbage collection. Triggered automatically when free string space < 256 bytes. Supports up to 2048 strings; disables if exceeded. Screen blanks during execution. Recommended for string-intensive routines.

!49 Boot device numbers (Read-Only)

A table of 3 values, !49(0) to !49(2), which holds the device numbers for the Boot drive, Program drive, and External drive, respectively. See also !50, !51, and the function @30.

!50 Boot drive numbers (Read-Only)

A table of 3 values, !50(0) to !50(2), which holds the drive numbers for the Boot drive, Program drive, and External drive, respectively. See also !49, !51, and the function @30.

!51 Disk swapping flag (Read-Only)

Defined by BOOTMAKER program. 0 = No swap required Non-zero = Disk swap required See also !49, !50, and the function @30.

!52 Most recent find location (Read-Only)

Holds location result of @2 or @25 find functions.

!53 2 MHz FGC flag

If 1, C128 attempts 2 MHz mode during fast garbage collect. No effect on C64. Automatically set for C128 users.

!55 Message record delimiter flag

See Undocumented features: .31.

!56 Message editor command state

Indicates editor command mode. See Undocumented features: !56.

!57 Editor prefix trigger

Defines key entering editor command mode. See Undocumented features: !57.

!58 Editor variable (Undocumented)

Under investigation. See Undocumented features: !58.

!59 Text-entry mode flag (Editor)

Non-zero indicates text-entry-only state. See Undocumented features: !59.

!60 Editor menu selection

Stores selected editor menu item. See Undocumented features: !60.

Next Section: ML Functions

Programming Features

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