When the interpreter has loaded at $1200, it executes a boot routine
at $7D79 which zeroes the internal clock, stores the current cursor
positions at their new addresses, and switches out the ROM Monitor and
Video RAM areas. It then loads itself down to commence at $0000, on
the way it loses the boot section and after the initial screen message
is printed this is wiped out too. Strangely enough even the initial
"36439 BYTES FREE" is built-in to that first message. PRINT
SIZE immediately after would produce 36592.
The list of RAM Monitor and S-BASIC entry points and work area adresses
is not a complete list, but it might assist those of you who are delving
into the interpreter with your disassembler.
| S-BASIC entry points / work area |
|
Address
|
Description |
|
$0000
|
Cold start monitor / BASC |
|
$0003
|
Get line to workarea adressed by DE ( unused, all calls to $004A
) |
|
$0006
|
New line |
|
$0009
|
New line if the cursor isn't positioned at line begin |
|
$000C
|
Print space |
|
$000F
|
Print tab. Sets the cursor to the next tab position |
|
$0012
|
Print character stroed in Accu |
|
$0015
|
Print message pointed to by DE ( unused, all calls to $0051 ) |
|
$0018
|
Print message pinted to by DE. Cursor characters are included
( unused, all calls to $0051 ) |
| $001B |
check if key is pressed |
| $001E |
check if SHIFT-BREAK is pressed |
|
$0021
|
Write info header to tape |
|
$0024
|
Write data to tape |
|
$0027
|
Read info header from tape |
|
$002A
|
Read data from tape |
|
$002D
|
Verify tape and program in RAM |
|
$0030
|
Melody play |
|
$0033
|
Time set |
|
$0038
|
Interrupt |
|
$003B
|
Read time |
|
$003E
|
Bell |
|
$0041
|
Set tempo |
|
$0044
|
Melody start |
|
$0047
|
Melody stop |
|
$004A
|
Get line from keyboard |
| $004D |
printer flag.
$16 ( or each other value >0 ) = plot on
$00 = plot off |
| $004E |
CONSOLE flag.
$00 = scrolling is suppressed
each other value executes scrolling |
| $004F |
input buffer length
$FF = BASIC 255 characters
$64 = monitor 100 characters |
| $0050 |
flag tape output
e.g. if >0 then a SAVE or LOAD command called by a program is
active |
| $0051 |
Print message pointed to by DE |
| $0054 |
current cursor position X |
| $0055 |
current cursor position Y |
| $0056 |
points to the first line to be scrolled ( Ymin ) |
| $0057 |
number of lines to be scrolled ( Ymax ) |
| $0058 |
check if key is pressed ( no repeat is possible ) |
| $005B |
points to the first column to be scrolled ( Xmin ) |
| $005C |
number of columns to be scrolled ( Xmax ) |
| $005D |
bits 3 - 0 background colour
bits 7 - 4 character colour |
| $005E |
clear character $00 to clear the screen |
| $005F |
contains character of the last key pressed |
| $0060 |
actual cursor character ( display code used )
$43 = alpha
$EF = graphic lower case
$FF = graphic |
| $0061 |
joystick subroutine |
| $0064 |
AM / PM flag
$00 = AM
$01 = PM |
| $0065 |
joystick value analog |
| $0066 |
joystick value digital |
$0067 -
$00A6 |
Control code address table. Contains the
address to jump to after the "PRINT CHR$"-statement or
a key with the CTRL-key down, as
explained here ( The "NOACT" shown there means it
will effect in an immediate return ). |
$00A7 -
$00D9 |
Concatination flag of Basic lines 0 ( $00A6 ) - 50 ( $00D9 ).
Used for identification of logical lines which logically represent
a Basic line listed on the screen. A Basic line can have up to 255
characters and by this it can exceed the length of a physical line
which has only the length of a 40-character screen line. Basic uses
this area to remember which lines are logically one Basic line.
The contents of this area is important e.g. while editing a Basic
line.
Example: If $00A7 contains $00 00 01 01 00 ... then physical lines
2 and 3 belong logically to the physical line 1. Note, line 1 is
addressed by $00A8 and note, line 0 has only one logical line (
no concatination ). A "$01" flag indicates it is a logical
line to the previous line containing $00 ( or $01 if more than 2
lines are logically one Basic line; as shown in the example ).
$00A7 - $00BF relates to the visible area and $00C0 - $00D8 to the
unvisible area which is shown if scrolling is performed by using
the SHIFT / Cursor UP/DOWN keys. $00D9 is used during a scroll operation
as a workarea. |
| $00EA |
Routine called from PEEK to access the V-RAM |
| $00F2 |
used to POKE to V-RAM |
$011C -
$011F |
table of 4 forbidden / suppressed printer characters ( HOME, CLR,
DEL, INS ) |
| $04A0 |
checks for Break condition
Z-flag is set on return if the condition is true |
| $04B6 |
Display to ASCII converter ( Accu ) |
| $04CD |
ASCII to Display code converter ( Accu ) |
$0EFC -
$0FFB |
ASCII to Display ( and vice versa ) conversion code table. $F0
= non-displayable character |
| $0A32 |
Tempo ( 1 - 7; 1 = quick, 7 = slow ) |
$0A33 -
$0A36 |
unused by Basic |
| $0A37 |
Duration |
| $0A38 |
Octave ( 1 = upper, 2 = middle, 3 = lower ) |
| $0A39 |
Frequency ( ratio ) |
$0FFC -
$121C |
is used by several routines as workarea, e.g. tape header, preparation
of the USING-format, keyboard input buffer.
The area $1000 - $11FF cannot be used for any purposes if you want
to prevent loss of data during RESET and returning to Basic. In
this case the monitor uses this area. |
$0FFC -
$107B |
tape header area |
| $0FFC |
file type stored |
| $0FFD |
file name |
| $100E |
file size |
| $1010 |
load address |
| $1012 |
executin address |
| $110F |
last line input buffer |
$121D -
$131C |
table used by keyboard-matrix to ASCII conversion |
$131D -
$1321 |
conversin table of additional defined CTRL-keys |
$1322 -
$13C1 |
DEF KEY function table in ASCII, any alterations to DEF KEY will
be stored here. 10 entries; each is 16 bytes in length and each
first byte contains the length of the text |
| $13C2 |
cold start of the RAM monitor |
$141C -
$1439 |
table contains monitor commands ( D, M, P, G, F, R, S, L, V, T
) and their related entry points |
| $1819 |
monitor output flag
>$00 output to printer |
| $1822 |
is where BASIC jumps to after loading, where the intial screen
message is displayed and subsequently gets wiped out as RAM is cleared
p to $FF00. If you don't want everything cleared then this is the
place to make alterations. Cold start Basic used only once at startup. |
| $1848 |
is where all future returns to BASIC from ROM Monitor jump, so
keeping RAM intact, Warm- / RESET-start of BASIC. |
| $1869 |
is where "Ready" gets displayed |
| $1872 |
is the main edit loop |
| $18FB |
starts the execution loop |
| $1915 |
check for TRON ( flag $38DD ) |
| $1930 |
Check BREAK |
| $19D0 |
is the routine for converting MZ-80K to MZ-700 programs addressed
by HL ( program line address ) |
| $20C7 |
is the error table and numbers |
| $2173 |
displays the current line number |
| $21A7 |
converts HL-hex to ASCII and stores it to $6A26 |
| $2287 |
TRON routine, finishes at $229E |
$242F -
$2458 |
which although contains code, is not used |
| $2AF5 |
starts the first keyword table, up to $2CA8 |
$2CA9 -
$30A8 |
is completely empty and this seems a likely place for any additions
you might like to make. If you use a tolkit this is the most favoured
spot for it, so dump this out before making changes. |
| $30A9 |
sees the start of the second keyword table up to the start of
keyword addresses. If you are using a toolkit or a peripheral device
which needs extra code placed somewhere, check on this area before
adding any extra routines. |
$30A9 -
$3146 |
keyword table for 2 bytes tokens prefixed by $FF ( commands ) |
$3147 -
$3206 |
is the keyword address table for tokens $80 - $DF |
$3207 -
$3264 |
is the keyword address table for tokens prefixed by $FE |
$3265 -
$3304 |
keyword table for 2 bytes tokens prefixed by $FF ( functions ) |
| $3807 |
is the address of GOTO. In most versions of Basic GOTO or GOSUB
start their searches for a line number from the top of the program,
which on a long listing or a frequently used subroutine can slow
down the running, the 700 BASIC doesn't.
When a Basic line is entered with either of these statements the
token keyword, $80 for GOTO or $81 for GOSUB, is followed by $0B
and the line number. When the program has been run once the byte
which follows the tokens gets changed to $0C, and the bytes containing
the line number get altered to the absolute address in memory where
the GOTO line is stored, so cutting down the time taken searching
for program lines. Naturally each time a line is added or edited
these byte get changed back to $0B followed by line number, as their
absolute addresses might then be different.
For more details read the Basic Internals. |
$38D3 -
$3901 |
is where pointers to the current program are stored |
| $38D3 |
string workarea pointer |
| $38D5 |
Stack pointer at start of interpreting ( e.g. by RUN, $FE00 ) |
| $38D7 |
number of files allowed |
| $38D8 |
on error flag
$00 = inactive
$01 = active
$02 = Resume active
|
| $38D9 |
CONT flag
$00 = can't continue ( set by GOTO, RUN, edit new line )
$01 = can continue ( set by STOP, END ) |
| $38DA |
address of text-string area |
| $38DC |
unused |
| $38DD |
Trace flag
$01 = TRON
$00 = TROFF |
| $38DE |
unused |
| $38DF |
AUTO flag
$00 = inactive
$01 = active |
| $38E0 |
pointer to next Basic line to interprete |
| $36E2 |
AUTO first line number ( line number for editor ) |
| $38E4 |
AUTO increment count |
| $38E6 |
current line number in work ( or $FFFF if not interpreting ) |
| $38E8 |
address of the line-in-error. ( ON ERROR GOTO / GOSUB ) |
| $38EA |
line-number of the line-in-error |
| $38EC |
address of next line behind the line-in-error |
| $38EE |
address of the error in the line-in-eror |
| $38F0 |
address of byte interpreting |
| $38F2 |
error number |
| $38F3 |
address pointer of the current line for CONT ( set by BREAK, END,
STOP ) |
| $38F5 |
current line number for CONT |
| $38F7 |
address pointer of the next line for CONT |
$38F9 -
$38FA |
unused |
| $38FB |
workarea for loop variables ( e.g. FOR A...NEXT A ) |
$38FD -
$38FF |
unused |
| $3900 |
counter of null-command ( unused routine ) |
| $3901 |
option base flag ( unused ) |
| $3D86 |
is the binary to decimal conversion routine; HL-hex into ASCII
and stored to (DE) |
| $3DB2 |
used by binary / decimal conversion, divides HL by DE and stores
one digit ASCII result |
| $4795 |
turns basic line addressed by (DE) into tokens addressed by (HL) |
| $49CD |
turns tokens addressed by (HL) back to text for listing addressed
by (DE) |
$4B72 -
$4D4F |
text of error messages ( each suffixed by $00 ) |
| $4D50 |
checks for integer less than 256 ( e.g. used on CHR$ )
(HL) points to the integer; result to accu ( and DE ) |
| $4D65 |
checks for integer over 255 ( e.g. used on MOVE )
(HL) points to the integer; result to DE |
| $4DCB |
plotter mode flag ( 1 text mode, 2 = graph ) |
| $4DCD |
print size flag. Contains $4E for normal ( 40 characters ), $4C
for large ( 26 characters ), and $53 for small ( 80 characters ) |
| $4EE0 |
flag for co-ordinates ( $44 = LINE, $4A = RLINE, $4D = MOVE, $52
= RMOVE ) |
| $528B |
checks all maths expressions and sets pointer (DE) to the result |
$6A0C -
$6A11 |
unused |
| $6A12 |
pointer to math memory 4 |
| $6A14 |
pointer to math memory 3 |
| $6A16 |
pointer to math memory 2 |
| $6A18 |
pointer to math memory 1 |
| $6A1A |
pointer to math memory COS(argument) |
| $6A1C |
pointer to math memory SIN(argument) |
| $6A1E |
sign of result trig. |
| $6A1F |
workarea RND |
| $6A21 |
workarea EXP |
| $6A22 |
sign EXP(argument) |
| $6A23 |
workarea EXP |
| $6A24 |
exponent for LN |
$6A25 -
$6A57 |
workarea for ASCII digits
$6A36 decimal point-place
$6A37 right-of-comma positions |
| $6A58 |
counter length of line; workarea for conversion Basic line to
tokens |
| $6A59 |
pointer to result for maths routines |
| $6A5B |
sign of result + / - |
| $6A5C |
workarea for stack pointer |
| $6A5E |
workarea for stack pointer |
| $6A60 |
overflow flag 0 / 1 |
| $6A61 |
exponent result * |
$6A63 -
$6A64 |
unused |
| $6A65 |
type of variable |
| $6A66 |
workarea exponent |
$6A67 -
$6A6D |
workarea mantissa |
| $6A6E |
workarea exponent |
$6A6F -
$6A75 |
workarea mantissa |
| $6A76 |
workarea exponent |
$6A77 -
$6A7D |
workarea mantissa |
| $6A7E |
pointer to real number |
| $6A80 |
flag skip spaces in number |
| $6A81 |
counter left-of-comma positions |
| $6A82 |
flag digit ready |
| $6A84 |
flag decimal-point |
$6AB3 -
$6AC1 |
more pointers to the current program |
| $6AB3 |
end of program; pointer to variables / defined functions |
| $6AB5 |
address of string variable storage |
| $6AB7 |
address for next string variable ( free area ) |
| $6AB9 |
pointer to maths memory |
| $6ABB |
pointer to start of RAM ( changed by LIMIT ). The area pointed
to can be used e.g. as resident part of machine code programs. |
| $6ABD |
top of RAM ( changed by LIMIT; $FF00 ) |
| $6ABF |
pointer to Basic file ( $6BCF ) |
$6AC1 -
$6AC2 |
workarea direct mode; conversion to tokens |
| $6BCF |
Basic program text area |
|
RAM Monitor entry points
|
|
Address
|
Description |
$141C -
$1439 |
table contains monitor commands ( D, M, P, G, F, R, S, L, V, T
) and their related entry points |
| $143A |
Print ( toggles $1819 $01 / $00 ) |
|
$1443
|
Save |
| $1469 |
Load |
|
$14A9
|
Verify |
| $14B8 |
Return |
|
$1545
|
Goto |
| $154A |
Dump |
|
$15BD
|
Memory set |
| $15F4 |
Find |
|
$165A
|
Transfer |
| $1819 |
monitor output flag
>$00 output to printer |
