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17-02-89/A\Info
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » CEEFAX disks » telesoftware12.adl |
| Filename: | 17-02-89/A\Info |
| Read OK: | ✔ |
| File size: | 2FBA bytes |
| Load address: | 0000 |
| Exec address: | FFFFFFFF |
File contents
This package will give Assembly language users additional memory space for
the assembling of object code from large source code files.
The assembly method described here is intended for those who already are
familiar with 6502 assembly on the BBC. A reasonable knowledge of this,
and BBC BASIC is assumed in the notes. Beginners would, in any case, be
unlikely to need the extra memory space made available by using this
system.
Minimum hardware requirements are:
Model B computer Cassette recorder BASIC (any version) Any wordprocessor.
Working from cassette will be very slow, and BASIC 2 or later is to be
preferred.
The Assembler built-in the BBC Micro is undoubtedly excellent, but has one
notable failing. This is the fact that the assembling Source program has
to reside in the machine along with the assembled Object code, often in
the same area that the Object code is neede d to run from.
From BASIC 2 onwards this is partly alleviated by the ability to use
offset assembly (OPT 4 - 7), however the main problem still exists; namely
that of having the Source code taking up valuable space.
If you are sufficiently involved in assembly language programming then you
may feel it worth investing in a more sophisticated assembler ROM that can
assemble from Source text files, sending the Object code directly to other
files. But there is an alternative approach which goes a long way to
solving the problem.
Most of us have, without thinking about it, used the computer to perform
simple calculations entered directly from the keyboard. What is not so
obvious is that almost the whole of the BASIC language structure is
available from the keyboard. This includes the assembler. Try the
following:
>P%=&C00
>[OPT 2:LDA #ASC"A":JSR &FFEE:RTS
>CALL &C00
You should find that the computer will print the letter 'A'. Notice that
the assembling line must start with [OPT and all the statements are on
that line. There is no need for the closing ] as the assembler is
automatically switched off at the end of the line.
This can be expanded using labels and variables, and spread over several
lines so:
>NEW
>base=&C00
>oswrch=&FFEE
>P%=base
>[OPT 2:LDX #&0A
>[OPT 2:.label
>[OPT 2:LDA #ASC"A"
>[OPT 2:JSR oswrch
>[OPT 2:DEX
>[OPT 2:BNE label
>[OPT 2:RTS
>CALL base
All of that is a rather contrived way of sending 10 'A's to the screen.
You could be forgiven for thinking that this is an unbelievably tedious
way of assembling code, particularly as the idea is to assemble very large
amounts!
Fortunately there is a way of fooling the computer into thinking that it
is receiving keyboard entry. This is done by using '*EXEC <file>'. What is
needed is a wordprocessor that can produce unformatted raw text with no
added control codes or (time wasting) padding spaces. Wordwise is ideal
for this or, if you have the MASTER series, the text editor. View, and
other wordprocessors can be used if the file is saved with the 'Write
Text' option.
If the previous lines are typed in and saved to a file named (say)
'source', then all you need to do when you want to assemble the code is to
type '*EXEC source'. Note that the variable/label stack will start at
LOMEM which will be PAGE+2 so if you want code to be assembled here then
you must either move LOMEM or use offset assembly and save and re-load the
Object code.
If, for example, you want to assemble your brilliant new game at &1900 and
you expect the code to be less than 8k, construct the file 'source' as
below.
NEW:LOMEM=&3900:base=&1900:P%=base (CR) [OPT 2: {code} (CR) [OPT 2: {code}
(CR) etc.
It should be noted that the lines of code must not exceed 255 characters
(about 6 lines of 40 column text) and for safety I usually stick to about
half of that. The fewer lines you have the faster the code assembles but
you gain nothing memory-wise as the source code exists in file form. Also
LOMEM must be set before any variables are used, otherwise you'll lose
them again!
An astute reader will have noticed that I have only used OPT 2, whereas
usually one needs to use two pass assembly within a FOR-NEXT loop, the FOR
variable being used to set OPT. When assembling from the keyboard or from
an EXEC file, only the current line exists in the computer's memory (at
&700 actually), so FOR-NEXT and REPEAT-UNTIL constructs can only be made
to operate over this line, which can't be more than 255 bytes long.
The solution is to use '*EXEC source' twice, adjusting the OPT variable
acordingly. Using OPTs 1-3, and 5-7 causes confusion. You end up with
repeated lines on the screen, so stick to 0-2, and 4-6. As you don't want
to reset the whole system with NEW each pass, you also need to split the
file into two parts. Call them 'init' and 'code'. Taking this one step
further 'code' can be made to re-run itself so:
'init' file :
NEW (CR)
LOMEM=&3900 (CR)
base=&1900 (CR)
zero=&70 (CR)
oswrch=&FFEE (CR)
osbyte=&FFF4 (CR)
I%=0 (CR)
*EXEC code (CR)
'code' file :
P%=base (CR)
[OPTI%: {code} (CR)
[OPTI%: {code} (CR)
etc.
IF I%=0 THEN I%=2:*EXEC code (CR)
All you now need to do is to type '*EXEC init', and let it get on with it.
Notice that all constants should be set in 'init' in the same way that you
would use a PROCinit in a 'real' program. I've spread the lines out in the
example to make this clearer. Also in 'code' the OPT variable will be
entered for every new line. Using one of the resident integers makes it a
little clearer and less tedious to enter than a real variable.
Ideally you want the labels and variables to take up as little room in the
variable stack as possible, thereby making the maximum possible space
available to the assembled code. Use all the resident integers where
possible. This will cost you no memory at all. P% (and in the case of
offset assembly, O%) are used by the assembler so are not available. I
suggest you use I% for the OPT variable. For other variables use minimum
possible abbreviations and real variables rather than non-resident
integers. The '%' takes a valuable byte out of the variable stack. Also
use lots of REMs and blank lines for clarity. They use up no memory at
all. The assembler drops out every line so REMs are quite possible, and in
fact clearer than comments. Purists will hate me for saying this, but
don't use unnecessary variables. Use the actual addresses for OS calls
etc., as below:
REM this is an A writer (CR)
(CR)
[OPTI%:.a1:LDA #ASC"A":LDX #&0A (CR)
(CR)
REM loop to here for more A's (CR)
(CR)
[OPTI%:.a2:JSR &FFEE:DEX:BNE a2 (CR)
(CR)
REM no more A's so exit (CR)
(CR)
[OPTI%:RTS (CR)
A lot of people follow labels with a space rather than a colon. I strongly
advise you not to, when using this method of assembly. From experience I
know it is very easy to accidentally remove spaces from a text file whilst
tidying up. Tedious when the error won 't be reported until the second
pass!
One problem that isn't obvious here is the computer's response to errors.
These will be reported in the usual way, but as you are assembling via the
'keyboard' there is no program for BASIC's error handler to stop, so it
will keep on trying to assemble with the error message being scrolled off
the top of the screen. Obviously you can't sit glued to the screen
watching for errors as they occur, and undetected ones can be extremely
difficult to identify, so an error handler has to be added.
The lines below should be put in at the very start of 'init' so that once
the code runs 'NEW' will wipe out the (no longer required) variables used.
The routine works by redirecting BRKV, where all errors pass. The new code
closes the current EXEC file, then puts BRKV back where it belongs. The
result is that you see the error message at the bottom of the screen. You
then know that the line above is the one containing the error.
LOMEM=&7000:brkv=&202:P%=&C00 (CR)
(CR)
[OPT2:.store:EQUW &FFFF (CR)
(CR)
[OPT2:.err:PHP:PHA:TXA:PHA:TYA:PHA (CR)
[OPT2:LDA #&77:JSR &FFF4 (CR)
[OPT2:SEI:LDA store:STA brkv (CR)
[OPT2:LDA store+1:STA brkv+1:CLI (CR)
[OPT2:PLA:TAY:PLA:TAX:PLA:PLP:JMP(brkv) (CR)
(CR)
[OPT2:.set:SEI (CR)
[OPT2:LDA brkv:STA store (CR)
[OPT2:LDA brkv+1:STA store+1 (CR)
[OPT2:LDA #err MOD256:STA brkv (CR)
[OPT2:LDA #err DIV256:STA brkv+1 (CR)
[OPT2:CLI:RTS (CR)
(CR)
CALL set (CR)
Be very careful to ensure that this bit of code doesn't itself contain
errors. I've used &C00 for the error code's location. This is normally a
safe place. The code is very short and could be put in one of several
other places if necessary.
With a little ingenuity you will find that almost all assembly can be done
from files like this, including lists and tables. These can sometimes be
pre-compiled in BASIC programs, and *LOAD used in conjunction with OSCLI
to locate them where they are required. Very occasionally there is a
problem that has to be solved with a procedure or function, which
obviously can't exist in a file. This is particularly true for BASIC 1
users who may need to synthesise the EQU and OSCLI operations. Fortunately
it is possible to tuck very small procedures away in memory and call them
when required. If you have a block of procedures that is less than 512
bytes long, and are careful about LOMEM it is possible to have it residing
at &900. Below is an arrangement that does just that.
procedures :
10DEFPROCa:PRINT"PROCa":ENDPROC
20DEFPROCb:PRINT"PROCb":ENDPROC
Save as 'PROC'
'init' file :
PAGE=&900 (CR)
LOAD"PROC" (CR)
(CR)
LOMEM=&7000: {etc. as before}
To run the whole suite type '*EXEC init'. This, or any later files can now
call the procedures or functions as they need to. If the procedures use
variables, they will be put safely on the variable stack above LOMEM.
Notice that I've used the maximum possible compression in the procedures
to save memory space. Also the LOAD command in 'init' must be on its own
line. Finally OLD must be used instead of NEW or the computer will lose
the program lines loaded!
A complete (rather contrived) set is as follows:
PROGRAM :
10DEFPROCa:CLS:PRINT'"All done!":ENDPROC
Save as 'PROC'
'init' file :
PAGE=&900 (CR)
LOAD"PROC" (CR)
(CR)
LOMEM=&7000 (CR)
brkv=&202 (CR)
P%=&C00 (CR)
(CR)
[OPT2:.store:EQUW &FFFF (CR)
(CR)
[OPT2:.err:PHP:PHA:TXA:PHA:TYA:PHA (CR)
[OPT2:LDA #&77:JSR &FFF4 (CR)
[OPT2:SEI:LDA store:STA brkv (CR)
[OPT2:LDA store+1:STA brkv+1:CLI (CR)
[OPT2:PLA:TAY:PLA:TAX:PLA:PLP:JMP (brkv) (CR)
(CR)
[OPT2:.set:SEI (CR)
[OPT2:LDA brkv:STA store (CR)
[OPT2:LDA brkv+1:STA store+1 (CR)
[OPT2:LDA #err MOD256:STA brkv (CR)
[OPT2:LDA #err DIV256:STA brkv+1 (CR)
[OPT2:CLI:RTS (CR)
(CR)
CALL set (CR)
OLD (CR)
LOMEM=&1A00 (CR)
base=&1900 (CR)
I%=0 (CR)
*EXEC code (CR)
'code' file :
P%=base (CR)
REM this is an A writer (CR)
(CR)
[OPTI%:.a1:LDX #&0A (CR)
(CR)
REM loop to here for more A's (CR)
(CR)
[OPTI%:.a2:LDA #ASC"A":JSR &FFEE:DEX:BNE a2 (CR)
(CR)
REM no more A's so exit (CR)
(CR)
[OPTI%:RTS (CR)
IF I%=2 THEN PROCa ELSE I%=2:*EXEC code (CR)
Once you develop really large Source code you will find that it won't all
fit in to one text file. This is not a problem. All you have to do is to
make files daisy-chain each other like the ones below.
file 2:
REM basic tools (CR)
(CR)
[OPTI%: {code} (CR)
etc
*EXEC ftools (CR)
file 3:
REM filing tools (CR)
(CR)
[OPTI%: {code} (CR)
etc
*EXEC mtools (CR)
file 8:
REM subroutines (CR)
(CR)
[OPTI%: {code} (CR)
etc
IF I%=6 THEN CLS:P.''"Finished" EL.I%=6:*EXEC btools (CR)
I use this method to produce a 16k Toolkit EPROM using offset assembly. It
requires 8 files and takes around five minutes to assemble from the DFS.
The machine used is a perfectly standard Model B with only Wordwise added.
If you stick to the format I've used here then the BASIC program 'PRINTER'
can be used to make a hard copy of your files. It is intended for use with
an Epson compatible printer using normal fan-fold paper.
The program prints a heading on each page with the filename and page
number. For clarity it will automatically strip off the '[OPTI %' and will
indent statements and comments, whilst leaving any BASIC untouched. There
is also an option to split the statements on to separate lines - this
really gobbles up paper but makes the code a delight to read.
00000000 54 68 69 73 20 70 61 63 6b 61 67 65 20 77 69 6c |This package wil|
00000010 6c 20 67 69 76 65 20 41 73 73 65 6d 62 6c 79 20 |l give Assembly |
00000020 6c 61 6e 67 75 61 67 65 20 75 73 65 72 73 20 61 |language users a|
00000030 64 64 69 74 69 6f 6e 61 6c 20 6d 65 6d 6f 72 79 |dditional memory|
00000040 20 73 70 61 63 65 20 66 6f 72 0d 74 68 65 20 61 | space for.the a|
00000050 73 73 65 6d 62 6c 69 6e 67 20 6f 66 20 6f 62 6a |ssembling of obj|
00000060 65 63 74 20 63 6f 64 65 20 66 72 6f 6d 20 6c 61 |ect code from la|
00000070 72 67 65 20 73 6f 75 72 63 65 20 63 6f 64 65 20 |rge source code |
00000080 66 69 6c 65 73 2e 0d 0d 54 68 65 20 61 73 73 65 |files...The asse|
00000090 6d 62 6c 79 20 6d 65 74 68 6f 64 20 64 65 73 63 |mbly method desc|
000000a0 72 69 62 65 64 20 68 65 72 65 20 69 73 20 69 6e |ribed here is in|
000000b0 74 65 6e 64 65 64 20 66 6f 72 20 74 68 6f 73 65 |tended for those|
000000c0 20 77 68 6f 20 61 6c 72 65 61 64 79 20 61 72 65 | who already are|
000000d0 0d 66 61 6d 69 6c 69 61 72 20 77 69 74 68 20 36 |.familiar with 6|
000000e0 35 30 32 20 61 73 73 65 6d 62 6c 79 20 6f 6e 20 |502 assembly on |
000000f0 74 68 65 20 42 42 43 2e 20 41 20 72 65 61 73 6f |the BBC. A reaso|
00000100 6e 61 62 6c 65 20 6b 6e 6f 77 6c 65 64 67 65 20 |nable knowledge |
00000110 6f 66 20 74 68 69 73 2c 0d 61 6e 64 20 42 42 43 |of this,.and BBC|
00000120 20 42 41 53 49 43 20 69 73 20 61 73 73 75 6d 65 | BASIC is assume|
00000130 64 20 69 6e 20 74 68 65 20 6e 6f 74 65 73 2e 20 |d in the notes. |
00000140 42 65 67 69 6e 6e 65 72 73 20 77 6f 75 6c 64 2c |Beginners would,|
00000150 20 69 6e 20 61 6e 79 20 63 61 73 65 2c 20 62 65 | in any case, be|
00000160 0d 75 6e 6c 69 6b 65 6c 79 20 74 6f 20 6e 65 65 |.unlikely to nee|
00000170 64 20 74 68 65 20 65 78 74 72 61 20 6d 65 6d 6f |d the extra memo|
00000180 72 79 20 73 70 61 63 65 20 6d 61 64 65 20 61 76 |ry space made av|
00000190 61 69 6c 61 62 6c 65 20 62 79 20 75 73 69 6e 67 |ailable by using|
000001a0 20 74 68 69 73 0d 73 79 73 74 65 6d 2e 0d 0d 4d | this.system...M|
000001b0 69 6e 69 6d 75 6d 20 68 61 72 64 77 61 72 65 20 |inimum hardware |
000001c0 72 65 71 75 69 72 65 6d 65 6e 74 73 20 61 72 65 |requirements are|
000001d0 3a 0d 0d 4d 6f 64 65 6c 20 42 20 63 6f 6d 70 75 |:..Model B compu|
000001e0 74 65 72 20 43 61 73 73 65 74 74 65 20 72 65 63 |ter Cassette rec|
000001f0 6f 72 64 65 72 20 42 41 53 49 43 20 28 61 6e 79 |order BASIC (any|
00000200 20 76 65 72 73 69 6f 6e 29 20 41 6e 79 20 77 6f | version) Any wo|
00000210 72 64 70 72 6f 63 65 73 73 6f 72 2e 0d 0d 57 6f |rdprocessor...Wo|
00000220 72 6b 69 6e 67 20 66 72 6f 6d 20 63 61 73 73 65 |rking from casse|
00000230 74 74 65 20 77 69 6c 6c 20 62 65 20 76 65 72 79 |tte will be very|
00000240 20 73 6c 6f 77 2c 20 61 6e 64 20 42 41 53 49 43 | slow, and BASIC|
00000250 20 32 20 6f 72 20 6c 61 74 65 72 20 69 73 20 74 | 2 or later is t|
00000260 6f 20 62 65 0d 70 72 65 66 65 72 72 65 64 2e 0d |o be.preferred..|
00000270 0d 54 68 65 20 41 73 73 65 6d 62 6c 65 72 20 62 |.The Assembler b|
00000280 75 69 6c 74 2d 69 6e 20 74 68 65 20 42 42 43 20 |uilt-in the BBC |
00000290 4d 69 63 72 6f 20 69 73 20 75 6e 64 6f 75 62 74 |Micro is undoubt|
000002a0 65 64 6c 79 20 65 78 63 65 6c 6c 65 6e 74 2c 20 |edly excellent, |
000002b0 62 75 74 20 68 61 73 20 6f 6e 65 0d 6e 6f 74 61 |but has one.nota|
000002c0 62 6c 65 20 66 61 69 6c 69 6e 67 2e 20 54 68 69 |ble failing. Thi|
000002d0 73 20 69 73 20 74 68 65 20 66 61 63 74 20 74 68 |s is the fact th|
000002e0 61 74 20 74 68 65 20 61 73 73 65 6d 62 6c 69 6e |at the assemblin|
000002f0 67 20 53 6f 75 72 63 65 20 70 72 6f 67 72 61 6d |g Source program|
00000300 20 68 61 73 0d 74 6f 20 72 65 73 69 64 65 20 69 | has.to reside i|
00000310 6e 20 74 68 65 20 6d 61 63 68 69 6e 65 20 61 6c |n the machine al|
00000320 6f 6e 67 20 77 69 74 68 20 74 68 65 20 61 73 73 |ong with the ass|
00000330 65 6d 62 6c 65 64 20 4f 62 6a 65 63 74 20 63 6f |embled Object co|
00000340 64 65 2c 20 6f 66 74 65 6e 20 69 6e 0d 74 68 65 |de, often in.the|
00000350 20 73 61 6d 65 20 61 72 65 61 20 74 68 61 74 20 | same area that |
00000360 74 68 65 20 4f 62 6a 65 63 74 20 63 6f 64 65 20 |the Object code |
00000370 69 73 20 6e 65 65 64 65 20 64 20 74 6f 20 72 75 |is neede d to ru|
00000380 6e 20 66 72 6f 6d 2e 0d 0d 46 72 6f 6d 20 42 41 |n from...From BA|
00000390 53 49 43 20 32 20 6f 6e 77 61 72 64 73 20 74 68 |SIC 2 onwards th|
000003a0 69 73 20 69 73 20 70 61 72 74 6c 79 20 61 6c 6c |is is partly all|
000003b0 65 76 69 61 74 65 64 20 62 79 20 74 68 65 20 61 |eviated by the a|
000003c0 62 69 6c 69 74 79 20 74 6f 20 75 73 65 0d 6f 66 |bility to use.of|
000003d0 66 73 65 74 20 61 73 73 65 6d 62 6c 79 20 28 4f |fset assembly (O|
000003e0 50 54 20 34 20 2d 20 37 29 2c 20 68 6f 77 65 76 |PT 4 - 7), howev|
000003f0 65 72 20 74 68 65 20 6d 61 69 6e 20 70 72 6f 62 |er the main prob|
00000400 6c 65 6d 20 73 74 69 6c 6c 20 65 78 69 73 74 73 |lem still exists|
00000410 3b 20 6e 61 6d 65 6c 79 0d 74 68 61 74 20 6f 66 |; namely.that of|
00000420 20 68 61 76 69 6e 67 20 74 68 65 20 53 6f 75 72 | having the Sour|
00000430 63 65 20 63 6f 64 65 20 74 61 6b 69 6e 67 20 75 |ce code taking u|
00000440 70 20 76 61 6c 75 61 62 6c 65 20 73 70 61 63 65 |p valuable space|
00000450 2e 0d 0d 49 66 20 79 6f 75 20 61 72 65 20 73 75 |...If you are su|
00000460 66 66 69 63 69 65 6e 74 6c 79 20 69 6e 76 6f 6c |fficiently invol|
00000470 76 65 64 20 69 6e 20 61 73 73 65 6d 62 6c 79 20 |ved in assembly |
00000480 6c 61 6e 67 75 61 67 65 20 70 72 6f 67 72 61 6d |language program|
00000490 6d 69 6e 67 20 74 68 65 6e 20 79 6f 75 0d 6d 61 |ming then you.ma|
000004a0 79 20 66 65 65 6c 20 69 74 20 77 6f 72 74 68 20 |y feel it worth |
000004b0 69 6e 76 65 73 74 69 6e 67 20 69 6e 20 61 20 6d |investing in a m|
000004c0 6f 72 65 20 73 6f 70 68 69 73 74 69 63 61 74 65 |ore sophisticate|
000004d0 64 20 61 73 73 65 6d 62 6c 65 72 20 52 4f 4d 20 |d assembler ROM |
000004e0 74 68 61 74 20 63 61 6e 0d 61 73 73 65 6d 62 6c |that can.assembl|
000004f0 65 20 66 72 6f 6d 20 53 6f 75 72 63 65 20 74 65 |e from Source te|
00000500 78 74 20 66 69 6c 65 73 2c 20 73 65 6e 64 69 6e |xt files, sendin|
00000510 67 20 74 68 65 20 4f 62 6a 65 63 74 20 63 6f 64 |g the Object cod|
00000520 65 20 64 69 72 65 63 74 6c 79 20 74 6f 20 6f 74 |e directly to ot|
00000530 68 65 72 0d 66 69 6c 65 73 2e 20 42 75 74 20 74 |her.files. But t|
00000540 68 65 72 65 20 69 73 20 61 6e 20 61 6c 74 65 72 |here is an alter|
00000550 6e 61 74 69 76 65 20 61 70 70 72 6f 61 63 68 20 |native approach |
00000560 77 68 69 63 68 20 67 6f 65 73 20 61 20 6c 6f 6e |which goes a lon|
00000570 67 20 77 61 79 20 74 6f 0d 73 6f 6c 76 69 6e 67 |g way to.solving|
00000580 20 74 68 65 20 70 72 6f 62 6c 65 6d 2e 0d 0d 4d | the problem...M|
00000590 6f 73 74 20 6f 66 20 75 73 20 68 61 76 65 2c 20 |ost of us have, |
000005a0 77 69 74 68 6f 75 74 20 74 68 69 6e 6b 69 6e 67 |without thinking|
000005b0 20 61 62 6f 75 74 20 69 74 2c 20 75 73 65 64 20 | about it, used |
000005c0 74 68 65 20 63 6f 6d 70 75 74 65 72 20 74 6f 20 |the computer to |
000005d0 70 65 72 66 6f 72 6d 0d 73 69 6d 70 6c 65 20 63 |perform.simple c|
000005e0 61 6c 63 75 6c 61 74 69 6f 6e 73 20 65 6e 74 65 |alculations ente|
000005f0 72 65 64 20 64 69 72 65 63 74 6c 79 20 66 72 6f |red directly fro|
00000600 6d 20 74 68 65 20 6b 65 79 62 6f 61 72 64 2e 20 |m the keyboard. |
00000610 57 68 61 74 20 69 73 20 6e 6f 74 20 73 6f 0d 6f |What is not so.o|
00000620 62 76 69 6f 75 73 20 69 73 20 74 68 61 74 20 61 |bvious is that a|
00000630 6c 6d 6f 73 74 20 74 68 65 20 77 68 6f 6c 65 20 |lmost the whole |
00000640 6f 66 20 74 68 65 20 42 41 53 49 43 20 6c 61 6e |of the BASIC lan|
00000650 67 75 61 67 65 20 73 74 72 75 63 74 75 72 65 20 |guage structure |
00000660 69 73 0d 61 76 61 69 6c 61 62 6c 65 20 66 72 6f |is.available fro|
00000670 6d 20 74 68 65 20 6b 65 79 62 6f 61 72 64 2e 20 |m the keyboard. |
00000680 54 68 69 73 20 69 6e 63 6c 75 64 65 73 20 74 68 |This includes th|
00000690 65 20 61 73 73 65 6d 62 6c 65 72 2e 20 54 72 79 |e assembler. Try|
000006a0 20 74 68 65 0d 66 6f 6c 6c 6f 77 69 6e 67 3a 0d | the.following:.|
000006b0 0d 3e 50 25 3d 26 43 30 30 0d 3e 5b 4f 50 54 20 |.>P%=&C00.>[OPT |
000006c0 32 3a 4c 44 41 20 23 41 53 43 22 41 22 3a 4a 53 |2:LDA #ASC"A":JS|
000006d0 52 20 26 46 46 45 45 3a 52 54 53 0d 3e 43 41 4c |R &FFEE:RTS.>CAL|
000006e0 4c 20 26 43 30 30 0d 0d 59 6f 75 20 73 68 6f 75 |L &C00..You shou|
000006f0 6c 64 20 66 69 6e 64 20 74 68 61 74 20 74 68 65 |ld find that the|
00000700 20 63 6f 6d 70 75 74 65 72 20 77 69 6c 6c 20 70 | computer will p|
00000710 72 69 6e 74 20 74 68 65 20 6c 65 74 74 65 72 20 |rint the letter |
00000720 27 41 27 2e 20 4e 6f 74 69 63 65 20 74 68 61 74 |'A'. Notice that|
00000730 0d 74 68 65 20 61 73 73 65 6d 62 6c 69 6e 67 20 |.the assembling |
00000740 6c 69 6e 65 20 6d 75 73 74 20 73 74 61 72 74 20 |line must start |
00000750 77 69 74 68 20 5b 4f 50 54 20 61 6e 64 20 61 6c |with [OPT and al|
00000760 6c 20 74 68 65 20 73 74 61 74 65 6d 65 6e 74 73 |l the statements|
00000770 20 61 72 65 20 6f 6e 0d 74 68 61 74 20 6c 69 6e | are on.that lin|
00000780 65 2e 20 54 68 65 72 65 20 69 73 20 6e 6f 20 6e |e. There is no n|
00000790 65 65 64 20 66 6f 72 20 74 68 65 20 63 6c 6f 73 |eed for the clos|
000007a0 69 6e 67 20 5d 20 61 73 20 74 68 65 20 61 73 73 |ing ] as the ass|
000007b0 65 6d 62 6c 65 72 20 69 73 0d 61 75 74 6f 6d 61 |embler is.automa|
000007c0 74 69 63 61 6c 6c 79 20 73 77 69 74 63 68 65 64 |tically switched|
000007d0 20 6f 66 66 20 61 74 20 74 68 65 20 65 6e 64 20 | off at the end |
000007e0 6f 66 20 74 68 65 20 6c 69 6e 65 2e 0d 0d 54 68 |of the line...Th|
000007f0 69 73 20 63 61 6e 20 62 65 20 65 78 70 61 6e 64 |is can be expand|
00000800 65 64 20 75 73 69 6e 67 20 6c 61 62 65 6c 73 20 |ed using labels |
00000810 61 6e 64 20 76 61 72 69 61 62 6c 65 73 2c 20 61 |and variables, a|
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17-02-89/A\Info.m0
17-02-89/A\Info.m1
17-02-89/A\Info.m2
17-02-89/A\Info.m4
17-02-89/A\Info.m5
.