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F/m\ctut1
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 » Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_20.ADF |
| Filename: | F/m\ctut1 |
| Read OK: | ✔ |
| File size: | 137C bytes |
| Load address: | 24204556 |
| Exec address: | 632F6D2E |
File contents
�PBoff
USING THE ASSEMBLER 3
~~~~~~~~~~~~~~~~~~~~~
I hope that you have been following me all right so far and enjoying some
experimenting with the assembler - it is through trying things out that we
learn.....
Hopefully I shall lead up to providing routines for simple arcade games
and also possibly adventure games too.
Having given the routines for printing to screen etc., you should be able
to make up instructions for a simple game or a menu or even location data
for an advenure game. How about some ideas......
In the meantime, I want to progress to some more interesting routines as
promised last time.
PLOTTING AND DRAWING
~~~~~~~~~~~~~~~~~~~~
These are performed by using VDU25 and PLOT becomes -
VDU25,p,x,y
where p is the PLOT number and x,y are the co-ordinates.
For MOVE use PLOT 4 and for DRAW use PLOT 5. Other PLOT numbers nan be
used, just as in BASIC, eg PLOT85 for filling triangles.
If you are setting up a series of PLOTs to draw a diagram, I have made up
a subroutine which read data in the form -
EQUB p:EQUW x:EQUW y
This needs the number of PLOTs loaded in A register and the address of
the data loaded in X and Y registers, as explained for previous routines,
before the routine is called.
.plot STXaddr:STYaddr+1:STAlen:LDY#0
.ploop LDA#25:JSR&FFEE \ VDU 25
LDX#5
.ploop2 LDA(addr),Y:JSR&FFEE \ enter data byte
INY:BNEnotover:INC addr+1
.notover DEX:BNEploop2
DEClen:BNE ploop
RTS
Note.
There are two variables in this listing which should be allocated before
the assembly loop so add -
15 addr=&70:len=80
You may also add the address of OSWRCH as a variable since it is easier to
write and saves remembering the address. Add - :oswrch=&FFEE to line 15.
This could even be shortened further (eg - os) provided it does not clash
with other variables.
It is usually good practice to allocate any variables in this way at the
beginning of the program.
The subroutine first enters the value 25 before calling OSWRCH then enters
the loop 'ploop2' which repeats 5 times to enter the 5 data bytes. The
variable 'len' is then decremented and if not zero then the routine
branches back to 'ploop1' for the next plot. If the data is longer than
255 bytes, Y register will return to zero and the branch to 'notover' will
not occur so that the high byte of 'addr' is incremented.
The Print routine could be modified in a similar way to enable it to print
longer text as it will only print up to 255 characters at present.
USER DEFINED CHARACTERS
~~~~~~~~~~~~~~~~~~~~~~~
These are defined by VDU23,char,a,b,c,d,e,f,g,h as in BASIC and this
routine will set up any number of characters from number 224 in sequnce.
Itwill read a series of data lines in the same way as the above routine.
The data can be entered, following the label '.chardata', as -
EQUB a:EQUB b:EQUB c:...........EQUB h
This can be simplified by using EQUD:EQUD but the numbers must be in hex
and each four digits must entered in reverse order as EQUD enters them in
reverse order. This then becomes -
EQUD &dcba:EQUD &hgfe
This routine needs the variables, temp=&81 and oswrch=&FFEE, entering in
line 15 as mentioned above.
.chars LDY#0:LDX#224
.chloop1 STXtemp
LDA#23:JSRoswrch \ VDU 23
TXA:JSRoswrch \ character no.
LDX#8
.chloop2 LDAchdata,Y \ read data byte
JSRoswrch
INY
DEX
BNEchloop2
LDXtemp \ reload char no.
INX \ increment char no.
CPX#242 \ last char no. +1
BNEchloop1
RTS
X register is loaded with 224, the first character value, and this is
stored in 'temp' within loop 'chloop1' since X register is used in the
second loop to count the 8 data bytes. A register is first loaded with 23
then the value in X to give the first two parts of the command. The loop
'chloop2' then loads the 8 data bytes. Register X is then loaded from
'temp' and incremented before repeating the process for the next
character. When the final character definition is completed, the routine
does not branch back as the comparison is met. The value of this must be
entered according to the number of characters to be defined.
This routine uses the Indexed Addressing mode and as written can only be
used once in the program. If some characters need to be redefined during
the running of a program, it should be possible to re-write the code in a
similar way to the print routine so that some could be re-defined from a
second set of data. How about trying this? You would need to do the
characters in reverse order - say from 250 down to 224 and from say 230 to
224 to re-define these. I will cover this later if needed.
I hope to cover key entry routines for making menu choices and moving
characters about the screen next time.
00000000 80 50 42 6f 66 66 0d 55 53 49 4e 47 20 54 48 45 |.PBoff.USING THE| 00000010 20 41 53 53 45 4d 42 4c 45 52 20 33 0d 7e 7e 7e | ASSEMBLER 3.~~~| 00000020 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e |~~~~~~~~~~~~~~~~| 00000030 7e 7e 0d 49 1a 20 68 6f 70 65 20 74 68 61 74 20 |~~.I. hope that | 00000040 79 6f 75 20 68 61 76 65 20 62 65 65 6e 20 66 6f |you have been fo| 00000050 6c 6c 6f 77 69 6e 67 20 6d 65 20 61 6c 6c 20 72 |llowing me all r| 00000060 69 67 68 74 20 73 6f 20 66 61 72 20 61 6e 64 20 |ight so far and | 00000070 65 6e 6a 6f 79 69 6e 67 20 73 6f 6d 65 0d 65 78 |enjoying some.ex| 00000080 70 65 72 69 6d 65 6e 74 69 6e 67 20 77 69 74 68 |perimenting with| 00000090 20 74 68 65 20 61 73 73 65 6d 62 6c 65 72 20 2d | the assembler -| 000000a0 20 69 74 20 69 73 20 74 68 72 6f 75 67 68 20 74 | it is through t| 000000b0 72 79 69 6e 67 20 74 68 69 6e 67 73 20 6f 75 74 |rying things out| 000000c0 20 74 68 61 74 20 77 65 0d 6c 65 61 72 6e 2e 2e | that we.learn..| 000000d0 2e 2e 2e 0d 0d 48 6f 70 65 66 75 6c 6c 79 20 49 |.....Hopefully I| 000000e0 20 73 68 61 6c 6c 20 6c 65 61 64 20 75 70 1a 20 | shall lead up. | 000000f0 74 6f 1a 20 70 72 6f 76 69 64 69 6e 67 1a 20 72 |to. providing. r| 00000100 6f 75 74 69 6e 65 73 20 66 6f 72 20 73 69 6d 70 |outines for simp| 00000110 6c 65 20 61 72 63 61 64 65 20 67 61 6d 65 73 0d |le arcade games.| 00000120 61 6e 64 20 61 6c 73 6f 20 70 6f 73 73 69 62 6c |and also possibl| 00000130 79 20 61 64 76 65 6e 74 75 72 65 20 67 61 6d 65 |y adventure game| 00000140 73 20 74 6f 6f 2e 0d 0d 48 61 76 69 6e 67 20 67 |s too...Having g| 00000150 69 76 65 6e 20 74 68 65 20 72 6f 75 74 69 6e 65 |iven the routine| 00000160 73 20 66 6f 72 20 70 72 69 6e 74 69 6e 67 1a 20 |s for printing. | 00000170 74 6f 20 73 63 72 65 65 6e 20 65 74 63 2e 2c 20 |to screen etc., | 00000180 79 6f 75 20 73 68 6f 75 6c 64 20 62 65 20 61 62 |you should be ab| 00000190 6c 65 0d 74 6f 20 6d 61 6b 65 20 75 70 20 69 6e |le.to make up in| 000001a0 73 74 72 75 63 74 69 6f 6e 73 20 66 6f 72 20 61 |structions for a| 000001b0 20 73 69 6d 70 6c 65 1a 20 67 61 6d 65 20 6f 72 | simple. game or| 000001c0 20 61 20 6d 65 6e 75 20 6f 72 20 65 76 65 6e 20 | a menu or even | 000001d0 6c 6f 63 61 74 69 6f 6e 20 64 61 74 61 0d 66 6f |location data.fo| 000001e0 72 20 61 6e 20 61 64 76 65 6e 75 72 65 20 67 61 |r an advenure ga| 000001f0 6d 65 2e 20 20 48 6f 77 20 61 62 6f 75 74 20 73 |me. How about s| 00000200 6f 6d 65 20 69 64 65 61 73 2e 2e 2e 2e 2e 2e 0d |ome ideas.......| 00000210 0d 49 6e 20 74 68 65 20 6d 65 61 6e 74 69 6d 65 |.In the meantime| 00000220 2c 20 49 20 77 61 6e 74 20 74 6f 20 70 72 6f 67 |, I want to prog| 00000230 72 65 73 73 20 74 6f 1a 20 73 6f 6d 65 1a 20 6d |ress to. some. m| 00000240 6f 72 65 20 69 6e 74 65 72 65 73 74 69 6e 67 20 |ore interesting | 00000250 72 6f 75 74 69 6e 65 73 20 61 73 0d 70 72 6f 6d |routines as.prom| 00000260 69 73 65 64 20 6c 61 73 74 20 74 69 6d 65 2e 0d |ised last time..| 00000270 0d 50 4c 4f 54 54 49 4e 47 20 41 4e 44 20 44 52 |.PLOTTING AND DR| 00000280 41 57 49 4e 47 0d 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e |AWING.~~~~~~~~~~| 00000290 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 0d 54 68 65 73 65 |~~~~~~~~~~.These| 000002a0 20 61 72 65 20 70 65 72 66 6f 72 6d 65 64 20 62 | are performed b| 000002b0 79 20 75 73 69 6e 67 20 56 44 55 32 35 20 61 6e |y using VDU25 an| 000002c0 64 20 50 4c 4f 54 20 62 65 63 6f 6d 65 73 20 2d |d PLOT becomes -| 000002d0 0d 0d 20 20 20 20 20 20 20 20 20 56 44 55 32 35 |.. VDU25| 000002e0 2c 70 2c 78 2c 79 0d 0d 77 68 65 72 65 20 70 20 |,p,x,y..where p | 000002f0 69 73 20 74 68 65 20 50 4c 4f 54 20 6e 75 6d 62 |is the PLOT numb| 00000300 65 72 20 61 6e 64 20 78 2c 79 20 61 72 65 20 74 |er and x,y are t| 00000310 68 65 20 63 6f 2d 6f 72 64 69 6e 61 74 65 73 2e |he co-ordinates.| 00000320 0d 0d 46 6f 72 20 4d 4f 56 45 20 75 73 65 20 50 |..For MOVE use P| 00000330 4c 4f 54 20 34 20 61 6e 64 20 66 6f 72 20 44 52 |LOT 4 and for DR| 00000340 41 57 1a 20 20 75 73 65 1a 20 50 4c 4f 54 20 35 |AW. use. PLOT 5| 00000350 2e 20 20 4f 74 68 65 72 20 50 4c 4f 54 20 6e 75 |. Other PLOT nu| 00000360 6d 62 65 72 73 20 6e 61 6e 20 62 65 0d 75 73 65 |mbers nan be.use| 00000370 64 2c 20 6a 75 73 74 20 61 73 20 69 6e 20 42 41 |d, just as in BA| 00000380 53 49 43 2c 20 65 67 20 50 4c 4f 54 38 35 20 66 |SIC, eg PLOT85 f| 00000390 6f 72 20 66 69 6c 6c 69 6e 67 20 74 72 69 61 6e |or filling trian| 000003a0 67 6c 65 73 2e 0d 0d 49 66 20 79 6f 75 20 61 72 |gles...If you ar| 000003b0 65 20 73 65 74 74 69 6e 67 20 75 70 20 61 20 73 |e setting up a s| 000003c0 65 72 69 65 73 20 6f 66 20 50 4c 4f 54 73 20 74 |eries of PLOTs t| 000003d0 6f 1a 20 64 72 61 77 20 61 20 64 69 61 67 72 61 |o. draw a diagra| 000003e0 6d 2c 20 49 20 68 61 76 65 20 6d 61 64 65 20 75 |m, I have made u| 000003f0 70 0d 61 20 73 75 62 72 6f 75 74 69 6e 65 20 77 |p.a subroutine w| 00000400 68 69 63 68 20 72 65 61 64 20 64 61 74 61 20 69 |hich read data i| 00000410 6e 20 74 68 65 20 66 6f 72 6d 20 2d 0d 0d 20 20 |n the form -.. | 00000420 20 20 20 20 20 20 20 45 51 55 42 20 70 3a 45 51 | EQUB p:EQ| 00000430 55 57 20 78 3a 45 51 55 57 20 79 0d 0d 54 68 69 |UW x:EQUW y..Thi| 00000440 73 20 6e 65 65 64 73 20 74 68 65 20 6e 75 6d 62 |s needs the numb| 00000450 65 72 20 6f 66 20 50 4c 4f 54 73 20 6c 6f 61 64 |er of PLOTs load| 00000460 65 64 20 69 6e 20 41 20 72 65 67 69 73 74 65 72 |ed in A register| 00000470 20 61 6e 64 1a 20 74 68 65 1a 20 61 64 64 72 65 | and. the. addre| 00000480 73 73 1a 20 6f 66 0d 74 68 65 20 64 61 74 61 20 |ss. of.the data | 00000490 6c 6f 61 64 65 64 20 69 6e 20 58 20 61 6e 64 20 |loaded in X and | 000004a0 59 20 72 65 67 69 73 74 65 72 73 2c 20 61 73 20 |Y registers, as | 000004b0 65 78 70 6c 61 69 6e 65 64 20 66 6f 72 20 70 72 |explained for pr| 000004c0 65 76 69 6f 75 73 20 72 6f 75 74 69 6e 65 73 2c |evious routines,| 000004d0 0d 62 65 66 6f 72 65 20 74 68 65 20 72 6f 75 74 |.before the rout| 000004e0 69 6e 65 20 69 73 20 63 61 6c 6c 65 64 2e 0d 0d |ine is called...| 000004f0 20 20 20 2e 70 6c 6f 74 20 53 54 58 61 64 64 72 | .plot STXaddr| 00000500 3a 53 54 59 61 64 64 72 2b 31 3a 53 54 41 6c 65 |:STYaddr+1:STAle| 00000510 6e 3a 4c 44 59 23 30 20 20 0d 20 20 20 2e 70 6c |n:LDY#0 . .pl| 00000520 6f 6f 70 20 4c 44 41 23 32 35 3a 4a 53 52 26 46 |oop LDA#25:JSR&F| 00000530 46 45 45 20 20 20 20 20 20 20 20 20 20 20 20 20 |FEE | 00000540 20 20 20 20 20 20 20 20 5c 20 56 44 55 20 32 35 | \ VDU 25| 00000550 0d 20 20 20 4c 44 58 23 35 20 20 0d 20 20 20 2e |. LDX#5 . .| 00000560 70 6c 6f 6f 70 32 20 4c 44 41 28 61 64 64 72 29 |ploop2 LDA(addr)| 00000570 2c 59 3a 4a 53 52 26 46 46 45 45 20 20 20 20 20 |,Y:JSR&FFEE | 00000580 20 20 20 20 20 20 20 20 20 20 5c 20 65 6e 74 65 | \ ente| 00000590 72 20 64 61 74 61 20 62 79 74 65 0d 20 20 20 49 |r data byte. I| 000005a0 4e 59 3a 42 4e 45 6e 6f 74 6f 76 65 72 3a 49 4e |NY:BNEnotover:IN| 000005b0 43 20 61 64 64 72 2b 31 20 20 0d 20 20 20 2e 6e |C addr+1 . .n| 000005c0 6f 74 6f 76 65 72 20 44 45 58 3a 42 4e 45 70 6c |otover DEX:BNEpl| 000005d0 6f 6f 70 32 0d 20 20 20 44 45 43 6c 65 6e 3a 42 |oop2. DEClen:B| 000005e0 4e 45 20 70 6c 6f 6f 70 20 20 0d 20 20 20 52 54 |NE ploop . RT| 000005f0 53 20 20 0d 0d 4e 6f 74 65 2e 0d 54 68 65 72 65 |S ..Note..There| 00000600 20 61 72 65 20 74 77 6f 20 76 61 72 69 61 62 6c | are two variabl| 00000610 65 73 20 69 6e 1a 20 74 68 69 73 1a 20 6c 69 73 |es in. this. lis| 00000620 74 69 6e 67 20 77 68 69 63 68 20 73 68 6f 75 6c |ting which shoul| 00000630 64 20 62 65 20 61 6c 6c 6f 63 61 74 65 64 20 62 |d be allocated b| 00000640 65 66 6f 72 65 0d 74 68 65 20 61 73 73 65 6d 62 |efore.the assemb| 00000650 6c 79 20 6c 6f 6f 70 20 73 6f 20 61 64 64 20 2d |ly loop so add -| 00000660 0d 0d 20 20 20 20 20 20 31 35 20 61 64 64 72 3d |.. 15 addr=| 00000670 26 37 30 3a 6c 65 6e 3d 38 30 0d 0d 59 6f 75 20 |&70:len=80..You | 00000680 6d 61 79 20 61 6c 73 6f 20 61 64 64 20 74 68 65 |may also add the| 00000690 20 61 64 64 72 65 73 73 20 6f 66 20 4f 53 57 52 | address of OSWR| 000006a0 43 48 20 61 73 20 61 20 76 61 72 69 61 62 6c 65 |CH as a variable| 000006b0 20 73 69 6e 63 65 20 69 74 20 69 73 20 65 61 73 | since it is eas| 000006c0 69 65 72 20 74 6f 0d 77 72 69 74 65 20 61 6e 64 |ier to.write and| 000006d0 20 73 61 76 65 73 20 72 65 6d 65 6d 62 65 72 69 | saves rememberi| 000006e0 6e 67 20 74 68 65 20 61 64 64 72 65 73 73 2e 20 |ng the address. | 000006f0 20 41 64 64 20 20 2d 20 3a 6f 73 77 72 63 68 3d | Add - :oswrch=| 00000700 26 46 46 45 45 20 74 6f 20 6c 69 6e 65 20 31 35 |&FFEE to line 15| 00000710 2e 0d 54 68 69 73 20 63 6f 75 6c 64 20 65 76 65 |..This could eve| 00000720 6e 20 62 65 20 73 68 6f 72 74 65 6e 65 64 20 66 |n be shortened f| 00000730 75 72 74 68 65 72 20 28 65 67 20 2d 20 20 6f 73 |urther (eg - os| 00000740 29 20 70 72 6f 76 69 64 65 64 20 69 74 20 64 6f |) provided it do| 00000750 65 73 20 6e 6f 74 20 63 6c 61 73 68 0d 77 69 74 |es not clash.wit| 00000760 68 20 6f 74 68 65 72 20 76 61 72 69 61 62 6c 65 |h other variable| 00000770 73 2e 0d 0d 49 74 20 69 73 20 75 73 75 61 6c 6c |s...It is usuall| 00000780 79 20 67 6f 6f 64 20 70 72 61 63 74 69 63 65 1a |y good practice.| 00000790 20 74 6f 1a 20 61 6c 6c 6f 63 61 74 65 20 61 6e | to. allocate an| 000007a0 79 20 76 61 72 69 61 62 6c 65 73 20 69 6e 20 74 |y variables in t| 000007b0 68 69 73 20 77 61 79 20 61 74 20 74 68 65 0d 62 |his way at the.b| 000007c0 65 67 69 6e 6e 69 6e 67 20 6f 66 20 74 68 65 20 |eginning of the | 000007d0 70 72 6f 67 72 61 6d 2e 0d 0d 0d 54 68 65 20 73 |program....The s| 000007e0 75 62 72 6f 75 74 69 6e 65 20 66 69 72 73 74 20 |ubroutine first | 000007f0 65 6e 74 65 72 73 20 74 68 65 20 76 61 6c 75 65 |enters the value| 00000800 20 32 35 20 62 65 66 6f 72 65 20 63 61 6c 6c 69 | 25 before calli| 00000810 6e 67 20 4f 53 57 52 43 48 20 74 68 65 6e 20 65 |ng OSWRCH then e| 00000820 6e 74 65 72 73 0d 74 68 65 20 6c 6f 6f 70 20 27 |nters.the loop '| 00000830 70 6c 6f 6f 70 32 27 20 77 68 69 63 68 20 72 65 |ploop2' which re| 00000840 70 65 61 74 73 20 35 20 74 69 6d 65 73 1a 20 74 |peats 5 times. t| 00000850 6f 1a 20 65 6e 74 65 72 1a 20 74 68 65 20 35 20 |o. enter. the 5 | 00000860 64 61 74 61 20 62 79 74 65 73 2e 20 20 54 68 65 |data bytes. The| 00000870 0d 76 61 72 69 61 62 6c 65 1a 20 27 6c 65 6e 27 |.variable. 'len'| 00000880 1a 20 69 73 1a 20 74 68 65 6e 1a 20 64 65 63 72 |. is. then. decr| 00000890 65 6d 65 6e 74 65 64 1a 20 61 6e 64 20 69 66 20 |emented. and if | 000008a0 6e 6f 74 20 7a 65 72 6f 20 74 68 65 6e 1a 20 74 |not zero then. t| 000008b0 68 65 1a 20 72 6f 75 74 69 6e 65 0d 62 72 61 6e |he. routine.bran| 000008c0 63 68 65 73 20 62 61 63 6b 20 74 6f 20 27 70 6c |ches back to 'pl| 000008d0 6f 6f 70 31 27 20 66 6f 72 20 74 68 65 1a 20 6e |oop1' for the. n| 000008e0 65 78 74 1a 20 70 6c 6f 74 2e 20 20 49 66 20 74 |ext. plot. If t| 000008f0 68 65 20 64 61 74 61 20 69 73 20 6c 6f 6e 67 65 |he data is longe| 00000900 72 20 74 68 61 6e 0d 32 35 35 20 62 79 74 65 73 |r than.255 bytes| 00000910 2c 20 59 20 72 65 67 69 73 74 65 72 20 77 69 6c |, Y register wil| 00000920 6c 20 72 65 74 75 72 6e 20 74 6f 20 7a 65 72 6f |l return to zero| 00000930 20 61 6e 64 20 74 68 65 20 62 72 61 6e 63 68 20 | and the branch | 00000940 74 6f 20 27 6e 6f 74 6f 76 65 72 27 20 77 69 6c |to 'notover' wil| 00000950 6c 0d 6e 6f 74 20 6f 63 63 75 72 20 73 6f 20 74 |l.not occur so t| 00000960 68 61 74 20 74 68 65 20 68 69 67 68 20 62 79 74 |hat the high byt| 00000970 65 20 6f 66 20 27 61 64 64 72 27 20 69 73 20 69 |e of 'addr' is i| 00000980 6e 63 72 65 6d 65 6e 74 65 64 2e 0d 0d 54 68 65 |ncremented...The| 00000990 20 50 72 69 6e 74 20 72 6f 75 74 69 6e 65 20 63 | Print routine c| 000009a0 6f 75 6c 64 20 62 65 20 6d 6f 64 69 66 69 65 64 |ould be modified| 000009b0 20 69 6e 20 61 20 73 69 6d 69 6c 61 72 20 77 61 | in a similar wa| 000009c0 79 20 74 6f 20 65 6e 61 62 6c 65 20 69 74 20 74 |y to enable it t| 000009d0 6f 20 70 72 69 6e 74 0d 6c 6f 6e 67 65 72 20 74 |o print.longer t| 000009e0 65 78 74 20 61 73 20 69 74 20 77 69 6c 6c 20 6f |ext as it will o| 000009f0 6e 6c 79 20 70 72 69 6e 74 20 75 70 20 74 6f 20 |nly print up to | 00000a00 32 35 35 20 63 68 61 72 61 63 74 65 72 73 20 61 |255 characters a| 00000a10 74 20 70 72 65 73 65 6e 74 2e 0d 0d 0d 55 53 45 |t present....USE| 00000a20 52 20 44 45 46 49 4e 45 44 20 43 48 41 52 41 43 |R DEFINED CHARAC| 00000a30 54 45 52 53 0d 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e |TERS.~~~~~~~~~~~| 00000a40 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 7e 0d 54 68 65 |~~~~~~~~~~~~.The| 00000a50 73 65 1a 20 61 72 65 1a 20 64 65 66 69 6e 65 64 |se. are. defined| 00000a60 1a 20 62 79 1a 20 56 44 55 32 33 2c 63 68 61 72 |. by. VDU23,char| 00000a70 2c 61 2c 62 2c 63 2c 64 2c 65 2c 66 2c 67 2c 68 |,a,b,c,d,e,f,g,h| 00000a80 1a 20 61 73 1a 20 69 6e 20 42 41 53 49 43 20 61 |. as. in BASIC a| 00000a90 6e 64 20 74 68 69 73 0d 72 6f 75 74 69 6e 65 20 |nd this.routine | 00000aa0 77 69 6c 6c 20 73 65 74 20 75 70 20 61 6e 79 20 |will set up any | 00000ab0 6e 75 6d 62 65 72 20 6f 66 20 63 68 61 72 61 63 |number of charac| 00000ac0 74 65 72 73 20 66 72 6f 6d 20 6e 75 6d 62 65 72 |ters from number| 00000ad0 20 32 32 34 20 69 6e 20 73 65 71 75 6e 63 65 2e | 224 in sequnce.| 00000ae0 0d 0d 49 74 1a 77 69 6c 6c 20 72 65 61 64 20 61 |..It.will read a| 00000af0 20 73 65 72 69 65 73 20 6f 66 20 64 61 74 61 20 | series of data | 00000b00 6c 69 6e 65 73 20 69 6e 20 74 68 65 20 73 61 6d |lines in the sam| 00000b10 65 20 77 61 79 20 61 73 20 74 68 65 20 61 62 6f |e way as the abo| 00000b20 76 65 20 72 6f 75 74 69 6e 65 2e 0d 54 68 65 20 |ve routine..The | 00000b30 64 61 74 61 20 63 61 6e 20 62 65 20 65 6e 74 65 |data can be ente| 00000b40 72 65 64 2c 20 66 6f 6c 6c 6f 77 69 6e 67 20 74 |red, following t| 00000b50 68 65 20 6c 61 62 65 6c 20 27 2e 63 68 61 72 64 |he label '.chard| 00000b60 61 74 61 27 2c 20 61 73 20 2d 0d 20 20 20 20 20 |ata', as -. | 00000b70 20 0d 20 20 20 20 20 20 45 51 55 42 20 61 3a 45 | . EQUB a:E| 00000b80 51 55 42 20 62 3a 45 51 55 42 20 63 3a 2e 2e 2e |QUB b:EQUB c:...| 00000b90 2e 2e 2e 2e 2e 2e 2e 2e 45 51 55 42 20 68 0d 0d |........EQUB h..| 00000ba0 54 68 69 73 20 63 61 6e 20 62 65 1a 20 73 69 6d |This can be. sim| 00000bb0 70 6c 69 66 69 65 64 1a 20 62 79 20 75 73 69 6e |plified. by usin| 00000bc0 67 20 45 51 55 44 3a 45 51 55 44 20 62 75 74 20 |g EQUD:EQUD but | 00000bd0 74 68 65 20 6e 75 6d 62 65 72 73 20 6d 75 73 74 |the numbers must| 00000be0 20 62 65 20 69 6e 20 68 65 78 0d 61 6e 64 20 65 | be in hex.and e| 00000bf0 61 63 68 20 66 6f 75 72 20 64 69 67 69 74 73 20 |ach four digits | 00000c00 6d 75 73 74 1a 20 65 6e 74 65 72 65 64 20 69 6e |must. entered in| 00000c10 20 72 65 76 65 72 73 65 20 6f 72 64 65 72 20 61 | reverse order a| 00000c20 73 20 45 51 55 44 20 65 6e 74 65 72 73 20 74 68 |s EQUD enters th| 00000c30 65 6d 20 69 6e 0d 72 65 76 65 72 73 65 20 6f 72 |em in.reverse or| 00000c40 64 65 72 2e 20 54 68 69 73 20 74 68 65 6e 20 62 |der. This then b| 00000c50 65 63 6f 6d 65 73 20 2d 0d 0d 20 20 20 20 20 20 |ecomes -.. | 00000c60 20 45 51 55 44 20 26 64 63 62 61 3a 45 51 55 44 | EQUD &dcba:EQUD| 00000c70 20 26 68 67 66 65 0d 0d 54 68 69 73 20 72 6f 75 | &hgfe..This rou| 00000c80 74 69 6e 65 20 6e 65 65 64 73 20 74 68 65 20 76 |tine needs the v| 00000c90 61 72 69 61 62 6c 65 73 2c 20 74 65 6d 70 3d 26 |ariables, temp=&| 00000ca0 38 31 20 61 6e 64 20 6f 73 77 72 63 68 3d 26 46 |81 and oswrch=&F| 00000cb0 46 45 45 2c 1a 20 65 6e 74 65 72 69 6e 67 1a 20 |FEE,. entering. | 00000cc0 69 6e 0d 6c 69 6e 65 20 31 35 20 61 73 20 6d 65 |in.line 15 as me| 00000cd0 6e 74 69 6f 6e 65 64 20 61 62 6f 76 65 2e 0d 0d |ntioned above...| 00000ce0 20 20 20 2e 63 68 61 72 73 20 4c 44 59 23 30 3a | .chars LDY#0:| 00000cf0 4c 44 58 23 32 32 34 20 0d 20 20 20 2e 63 68 6c |LDX#224 . .chl| 00000d00 6f 6f 70 31 20 53 54 58 74 65 6d 70 20 0d 20 20 |oop1 STXtemp . | 00000d10 20 4c 44 41 23 32 33 3a 4a 53 52 6f 73 77 72 63 | LDA#23:JSRoswrc| 00000d20 68 20 20 20 20 20 20 20 20 20 20 20 5c 20 56 44 |h \ VD| 00000d30 55 20 32 33 0d 20 20 20 54 58 41 3a 4a 53 52 6f |U 23. TXA:JSRo| 00000d40 73 77 72 63 68 20 20 20 20 20 20 20 20 20 20 20 |swrch | 00000d50 20 20 20 5c 20 63 68 61 72 61 63 74 65 72 20 6e | \ character n| 00000d60 6f 2e 0d 20 20 20 4c 44 58 23 38 20 0d 20 20 20 |o.. LDX#8 . | 00000d70 2e 63 68 6c 6f 6f 70 32 20 4c 44 41 63 68 64 61 |.chloop2 LDAchda| 00000d80 74 61 2c 59 20 20 20 20 20 20 20 5c 20 72 65 61 |ta,Y \ rea| 00000d90 64 20 64 61 74 61 20 62 79 74 65 0d 20 20 20 4a |d data byte. J| 00000da0 53 52 6f 73 77 72 63 68 0d 20 20 20 49 4e 59 20 |SRoswrch. INY | 00000db0 0d 20 20 20 44 45 58 20 0d 20 20 20 42 4e 45 63 |. DEX . BNEc| 00000dc0 68 6c 6f 6f 70 32 0d 20 20 20 4c 44 58 74 65 6d |hloop2. LDXtem| 00000dd0 70 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |p | 00000de0 20 20 20 20 20 20 5c 20 72 65 6c 6f 61 64 20 63 | \ reload c| 00000df0 68 61 72 20 6e 6f 2e 0d 20 20 20 49 4e 58 20 20 |har no.. INX | 00000e00 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000e10 20 20 20 20 20 20 20 5c 20 69 6e 63 72 65 6d 65 | \ increme| 00000e20 6e 74 20 63 68 61 72 20 6e 6f 2e 0d 20 20 20 43 |nt char no.. C| 00000e30 50 58 23 32 34 32 20 20 20 20 20 20 20 20 20 20 |PX#242 | 00000e40 20 20 20 20 20 20 20 20 20 20 20 5c 20 6c 61 73 | \ las| 00000e50 74 20 63 68 61 72 20 6e 6f 2e 20 2b 31 0d 20 20 |t char no. +1. | 00000e60 20 42 4e 45 63 68 6c 6f 6f 70 31 0d 20 20 20 52 | BNEchloop1. R| 00000e70 54 53 20 0d 0d 58 1a 20 72 65 67 69 73 74 65 72 |TS ..X. register| 00000e80 1a 20 69 73 1a 20 6c 6f 61 64 65 64 20 77 69 74 |. is. loaded wit| 00000e90 68 20 32 32 34 2c 20 74 68 65 20 66 69 72 73 74 |h 224, the first| 00000ea0 20 63 68 61 72 61 63 74 65 72 20 76 61 6c 75 65 | character value| 00000eb0 2c 20 61 6e 64 1a 20 74 68 69 73 1a 20 69 73 0d |, and. this. is.| 00000ec0 73 74 6f 72 65 64 1a 20 69 6e 1a 20 27 74 65 6d |stored. in. 'tem| 00000ed0 70 27 1a 20 77 69 74 68 69 6e 1a 20 6c 6f 6f 70 |p'. within. loop| 00000ee0 20 27 63 68 6c 6f 6f 70 31 27 20 73 69 6e 63 65 | 'chloop1' since| 00000ef0 20 58 20 72 65 67 69 73 74 65 72 20 69 73 20 75 | X register is u| 00000f00 73 65 64 20 69 6e 20 74 68 65 0d 73 65 63 6f 6e |sed in the.secon| 00000f10 64 20 6c 6f 6f 70 20 74 6f 20 63 6f 75 6e 74 20 |d loop to count | 00000f20 74 68 65 20 38 20 64 61 74 61 20 62 79 74 65 73 |the 8 data bytes| 00000f30 2e 20 20 41 20 72 65 67 69 73 74 65 72 20 69 73 |. A register is| 00000f40 20 66 69 72 73 74 20 6c 6f 61 64 65 64 20 77 69 | first loaded wi| 00000f50 74 68 20 32 33 0d 74 68 65 6e 20 74 68 65 20 76 |th 23.then the v| 00000f60 61 6c 75 65 20 69 6e 20 58 1a 20 74 6f 20 67 69 |alue in X. to gi| 00000f70 76 65 20 74 68 65 20 66 69 72 73 74 20 74 77 6f |ve the first two| 00000f80 20 70 61 72 74 73 20 6f 66 20 74 68 65 20 63 6f | parts of the co| 00000f90 6d 6d 61 6e 64 2e 20 20 54 68 65 20 6c 6f 6f 70 |mmand. The loop| 00000fa0 0d 27 63 68 6c 6f 6f 70 32 27 20 74 68 65 6e 20 |.'chloop2' then | 00000fb0 6c 6f 61 64 73 20 74 68 65 20 38 20 64 61 74 61 |loads the 8 data| 00000fc0 1a 20 62 79 74 65 73 2e 1a 20 20 52 65 67 69 73 |. bytes.. Regis| 00000fd0 74 65 72 1a 20 58 1a 20 69 73 20 74 68 65 6e 20 |ter. X. is then | 00000fe0 6c 6f 61 64 65 64 20 66 72 6f 6d 0d 27 74 65 6d |loaded from.'tem| 00000ff0 70 27 1a 1a 20 61 6e 64 1a 20 69 6e 63 72 65 6d |p'.. and. increm| 00001000 65 6e 74 65 64 1a 20 62 65 66 6f 72 65 1a 20 72 |ented. before. r| 00001010 65 70 65 61 74 69 6e 67 1a 20 74 68 65 1a 20 70 |epeating. the. p| 00001020 72 6f 63 65 73 73 1a 20 66 6f 72 1a 20 74 68 65 |rocess. for. the| 00001030 1a 20 6e 65 78 74 0d 63 68 61 72 61 63 74 65 72 |. next.character| 00001040 2e 1a 20 20 57 68 65 6e 20 74 68 65 20 66 69 6e |.. When the fin| 00001050 61 6c 20 63 68 61 72 61 63 74 65 72 20 64 65 66 |al character def| 00001060 69 6e 69 74 69 6f 6e 20 69 73 20 63 6f 6d 70 6c |inition is compl| 00001070 65 74 65 64 2c 20 74 68 65 20 72 6f 75 74 69 6e |eted, the routin| 00001080 65 0d 64 6f 65 73 20 6e 6f 74 1a 20 62 72 61 6e |e.does not. bran| 00001090 63 68 20 62 61 63 6b 20 61 73 20 74 68 65 20 63 |ch back as the c| 000010a0 6f 6d 70 61 72 69 73 6f 6e 20 69 73 20 6d 65 74 |omparison is met| 000010b0 2e 20 20 54 68 65 20 76 61 6c 75 65 20 6f 66 20 |. The value of | 000010c0 74 68 69 73 20 6d 75 73 74 20 62 65 0d 65 6e 74 |this must be.ent| 000010d0 65 72 65 64 20 61 63 63 6f 72 64 69 6e 67 20 74 |ered according t| 000010e0 6f 20 74 68 65 20 6e 75 6d 62 65 72 20 6f 66 20 |o the number of | 000010f0 63 68 61 72 61 63 74 65 72 73 20 74 6f 20 62 65 |characters to be| 00001100 20 64 65 66 69 6e 65 64 2e 0d 0d 54 68 69 73 20 | defined...This | 00001110 72 6f 75 74 69 6e 65 20 75 73 65 73 1a 20 74 68 |routine uses. th| 00001120 65 1a 20 49 6e 64 65 78 65 64 20 41 64 64 72 65 |e. Indexed Addre| 00001130 73 73 69 6e 67 20 6d 6f 64 65 20 61 6e 64 20 61 |ssing mode and a| 00001140 73 20 77 72 69 74 74 65 6e 20 63 61 6e 20 6f 6e |s written can on| 00001150 6c 79 20 62 65 0d 75 73 65 64 20 6f 6e 63 65 20 |ly be.used once | 00001160 69 6e 20 74 68 65 20 70 72 6f 67 72 61 6d 2e 1a |in the program..| 00001170 20 20 49 66 20 73 6f 6d 65 20 63 68 61 72 61 63 | If some charac| 00001180 74 65 72 73 20 6e 65 65 64 20 74 6f 20 62 65 20 |ters need to be | 00001190 72 65 64 65 66 69 6e 65 64 20 64 75 72 69 6e 67 |redefined during| 000011a0 0d 74 68 65 20 72 75 6e 6e 69 6e 67 20 6f 66 20 |.the running of | 000011b0 61 20 70 72 6f 67 72 61 6d 2c 20 69 74 1a 20 73 |a program, it. s| 000011c0 68 6f 75 6c 64 20 62 65 20 70 6f 73 73 69 62 6c |hould be possibl| 000011d0 65 20 74 6f 20 72 65 2d 77 72 69 74 65 20 74 68 |e to re-write th| 000011e0 65 20 63 6f 64 65 20 69 6e 20 61 0d 73 69 6d 69 |e code in a.simi| 000011f0 6c 61 72 20 77 61 79 20 74 6f 20 74 68 65 20 70 |lar way to the p| 00001200 72 69 6e 74 20 72 6f 75 74 69 6e 65 20 73 6f 1a |rint routine so.| 00001210 20 74 68 61 74 1a 20 73 6f 6d 65 20 63 6f 75 6c | that. some coul| 00001220 64 20 62 65 20 72 65 2d 64 65 66 69 6e 65 64 20 |d be re-defined | 00001230 66 72 6f 6d 20 61 0d 73 65 63 6f 6e 64 20 73 65 |from a.second se| 00001240 74 20 6f 66 20 64 61 74 61 2e 20 20 48 6f 77 20 |t of data. How | 00001250 61 62 6f 75 74 20 74 72 79 69 6e 67 20 74 68 69 |about trying thi| 00001260 73 3f 20 20 59 6f 75 1a 20 77 6f 75 6c 64 1a 20 |s? You. would. | 00001270 6e 65 65 64 1a 20 74 6f 1a 20 64 6f 1a 20 74 68 |need. to. do. th| 00001280 65 0d 63 68 61 72 61 63 74 65 72 73 20 69 6e 20 |e.characters in | 00001290 72 65 76 65 72 73 65 20 6f 72 64 65 72 20 2d 20 |reverse order - | 000012a0 73 61 79 20 66 72 6f 6d 20 32 35 30 20 64 6f 77 |say from 250 dow| 000012b0 6e 20 74 6f 20 32 32 34 20 61 6e 64 20 66 72 6f |n to 224 and fro| 000012c0 6d 20 73 61 79 20 32 33 30 20 74 6f 0d 32 32 34 |m say 230 to.224| 000012d0 20 74 6f 20 72 65 2d 64 65 66 69 6e 65 20 74 68 | to re-define th| 000012e0 65 73 65 2e 20 20 49 20 77 69 6c 6c 20 63 6f 76 |ese. I will cov| 000012f0 65 72 20 74 68 69 73 20 6c 61 74 65 72 20 69 66 |er this later if| 00001300 20 6e 65 65 64 65 64 2e 0d 0d 49 1a 20 68 6f 70 | needed...I. hop| 00001310 65 1a 20 74 6f 1a 20 63 6f 76 65 72 1a 20 6b 65 |e. to. cover. ke| 00001320 79 1a 20 65 6e 74 72 79 20 72 6f 75 74 69 6e 65 |y. entry routine| 00001330 73 20 66 6f 72 20 6d 61 6b 69 6e 67 20 6d 65 6e |s for making men| 00001340 75 20 63 68 6f 69 63 65 73 20 61 6e 64 20 6d 6f |u choices and mo| 00001350 76 69 6e 67 0d 63 68 61 72 61 63 74 65 72 73 20 |ving.characters | 00001360 61 62 6f 75 74 20 74 68 65 20 73 63 72 65 65 6e |about the screen| 00001370 20 6e 65 78 74 20 74 69 6d 65 2e 0d | next time..| 0000137c
F/m\ctut1.m0
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