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2liners/the art of 2-liners/SCRN_PLOT_your_sound_routine.md
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# SCRN/PLOT your 6502/ASM sound routine (or any other)
# PRINT/PLOT your 6502/ASM sound routine (or any other)
This article will explain a new (?) technique to poke ASM (machine language) subroutines using Applesoft (without using ``POKE``s at ALL) and actually spare several characters if you're into 2-liners.
## 6502 Subroutines in 2-liners
@ -247,29 +247,37 @@ Anyway none of these variations are short enough.
Can we do better ? Of course.
## New technique: PRINT/PLOT hexadecimal
So here comes the technique I've developed for this particular case.
So here comes the technique I've developed to help Applesoft write hexadecimal values in memory.
Notice that it can be used for all kinds of subroutines .... just be aware that we're "printing" routines and that the TEXT page lines are not sequential (line 1 is not in $400+40 chars). It works with any value from 0 to 255 and it's almost as easy as to type the actual hexadecimal values in the monitor.
It involves using four very simple instructions: PRINT, SCRN, COLOR and PLOT.
This new (?) technique involves using four very simple instructions: PRINT, SCRN, COLOR and PLOT.
Using the GR/TEXT capabilities of Applesoft we will poke a 6502 routine in TEXT page 1.
We will be using the GR/TEXT capabilities of Applesoft to poke a program in TEXT page 1.
Notice that it can be used for all kinds of subroutines .... just be aware that we're ``PRINT``ing values in memory and that the TEXT page lines are not sequential (line 1 is not in $400+40 chars). It works with any value from 0 to 255 and it's almost as easy as to type the actual hexadecimal values in the monitor.
How does it work ?
### PRINT
First we start from our 14 routine bytes: A6 07 A4 06 AD 30 C0 88 D0 FD CA D0 F5 60
First we start from our 14 routine bytes:
```A6 07 A4 06 AD 30 C0 88 D0 FD CA D0 F5 60```
We leave every number as it is, but we replace all the letters with new letters according to this:
A becomes J, B becomes K, C->L, D->M, E->N and F becomes O.
We now have J6 07 J4 06 JM 30 L0 88 M0 OM LJ M0 O5 60
We now have
```J6 07 J4 06 JM 30 L0 88 M0 OM LJ M0 O5 60```
We will now take advantage of the GR/TEXT screen and the SCRN function.
We now that TEXT page 1 and Lores page 1 share the same memory location, it starts in $400. Also one line of text is represented as 2 lines of lores graphics.
We are going to print every low-nibble (4 bits) of each char on line 1 of TEXT (which is line 0 of GR), this means we print "6746M0080MJ050"
We are going to print every low-nibble (4 bits) of each character on line 1 of TEXT (which is line 0 of GR), this means we rearrange all characters in even positions in the string in another string.
```
PRINT "6746M0080MJ050"
```
And we will print every high-nibble of each char on line 2 of TEXT (which is line 2 of GR), this means we print "J0J0J3L8MOLMO6"
And we will print every high-nibble of each character on line 2 of TEXT (which is line 2 of GR). We rearrange all characters in odd positions in another string
```
PRINT "J0J0J3L8MOLMO6"
```
The result is the following:
@ -292,9 +300,11 @@ The colors in line 0 correspond to the low-nibble (4 bits) of the bytes in $400-
And of course, the same goes for lines 2 & 3... Now all we have to do is copy the points in GR line 2 (low-nibbles of bytes in $480-$48D) to line 1 (high nibbles of bytes in $400-$40D).
The result is that in line 0 and 1 of GR, we'll have our sound routine.
We do this simply by getting the color of the points in line 2 with a ``SCRN(X,2)``, change the color using the ``COLOR`` statement and ``PLOT`` a new point in line 1 with that color.
Here's the resulting code:
The result is that in line 0 and 1 of GR (or TEXT line 1), we'll have our sound routine.
Here's the code:
```
0 HOME: REM 4 chars (not counted)
1 ?"6746M0080MJ050": REM 17+1 chars
@ -304,18 +314,17 @@ Here's the resulting code:
5 PLOT I,1: REM +7+1 chars = 71 chars we PLOT it on line 1, actually adding 16*color to the byte in $400+I
6 NEXT : REM +4 chars = 75 chars
```
Even with the "HOME" statement at first (which is needed but might already be included in your 2-liner), we have 75+4+1 chars = 80 chars
Even with the ``HOME`` statement at first (which is needed but might already be included in your 2-liner), we have 75+4+1 chars = 80 chars
This is still better than the traditional POKE technique ...
The main routine (the ``FOR/NEXT`` loop) "only" takes 39 characters.
This method can be used to POKE/PLOT longer routines ... just make sure to take into account the fact that one line is 40 chars max, so if you need to handle more bytes, simply add a embracing loop to repeat as needed ... don't forget you can do "NEXT I,J" instead of "NEXT:NEXT" !
Of course, if you need line 1 of TEXT or line 0 of GR, you'll see the routine ... it's probably better using Hires 2-liners....
Can we do even better ? Not that I know of if you try to use pseudo-hexadecimal in your code.
## One last thing
Roger Wagner's assembly lines contains another routine to handle sound that might be very useful for 2-liners.
@ -349,11 +358,6 @@ The 24 bytes routine uses 95 characters by itself ... it's almost as good as the
130 CALL 1024 , I, 10
140 NEXT
```
I hope you enjoyed this little tutorial on "how I did it" ! ....
Can you do better than this ? If so, don't hesitate to post, I'd be happy to see what you've come up with !
---
#### Licence
See [license](LICENSE.md)