Editor's note: The information contained in this article may be outdated and/or inaccurate.
Well, I just had myself a good time converting
UNITCONV to ASM. Now I got the program to run a little bit faster, and
the menus are cooler. Im probably going to rewrite it so its only one
program, instead of 100 (exaggeration). I also want to get rid of the CONV
list, and that should clear up A LOT of space. Im trying to get a hold
of all simple little programs that you probibly use for math and science
to cheat on the exams so I can make them smaller and faster by programming
them in ASM. Also, another ASM programmer I know of is trying to work out
a new compression program that works kinda like SQUISH and ZASMLOAD, but
itll be one file that converts and executes. Dont be looking for it very
soon, though. Theres a few things he needs to work out.
Welcome, friends. Today is the day that
you learn how to make a GOOD ASM program. In order to do this, I will have
to teach you about labels. A label is just as it sounds. It's the same
in BASIC as it is in ASM. The difference is how you jump to the label that
makes ASM difficult.
Remember in good old BASIC how you could
only have one-character labels? Well, ASM makes labels a lot more fun and
easier to remember my letting you determine the length and names of your
labels. To write a label in a program, you just type a word or phrase in
the first column and place a colon after it, like so:
Remember how I always used to tell you
that the commands in an ASM program have to be in the first column? Well,
this is because the assembler is stupid. It cant tell the difference between
a label and a command, so you have to make the two different by putting
the commands in the second column, or the position, and the labels
in the first column, or home position. I named the label 'FIRST_LABEL'
instead of '1ST_LABEL' or 'FIRST LABEL' because you can't put a number
as the first digit of a label, and you can't use spaces. The colon is also
VERY important. Without the colon, the assembler thinks the label is just
Now, "How do you jump to a label,
Phil?" you ask? Well, the command you'd use to jump is 'jp', short
for 'JUMP'. Get it? I'll show you an example that will jump to the label
'jp' IS A COMMAND, so therefore, it MUST
be in the position, like 'ld' or 'cp'. Okay, you have labels now,
and you can jump to them. Now it's time for an 'If...Then Goto...' command.
These commands are what make up the body on the more complex ASM programs.
Remember good ol' 'COMPARE', or 'cp'? Well, when you use that command comparing
two numbers, the output will either be zero, or 'z', or not zero, 'nz'
(If you are confused about comparing, refer to The ASM Logs vol. 2). (The
cp command needs to have the accumulator defined, or the variable a
defined in order to work. It outputs to z. but thats not important now.)
An 'If...Then Goto...' command can only read 'If zero Then Goto...' or
'If not zero Then Goto...' in ASM, so programmers have to get creative.
Let's compare two numbers:
Now, since 'a' equals five and you are
subtracting 5 from 'a', the output will be zero, right? I order to jump
to a label in this statement, we would add either a 'z' or an 'nz' to the
'jp' command ('z' being zero, and 'nz' being not zero). The command 'If
a-5=zero Then Goto FIRST_LABEL' would look like this in ASM:
Now just add on to this more 'cp' commands,
and you can compare 'a' to any thing you want in a series (you dont have
to keep redefining a), like so:
Also, you can put in 'nz' for 'z' if you
want the program to jump if the answer is not zero, like so:
Labels do not HAVE to be jumped to. Just
like how you really don't have to do this in BASIC:
You don't have to do this in ASM:
The same lines without the 'jp' command
would accomplish the same task, and take up less memory.
It's time to make another program!!! This
time, it will be a few simple 'cp...jp' commands. Remember to put in your
head like so:
#define equ .equ
#define EQU .equ
#define end .end
Now, program the following in notepad or
This means "If 'a' minus 5 equals
zero, jump to label, but if not, jump back home and try again."
And this means "Store 'a', or 1, into
BASIC's X and exit the program"
This means "Store 'a', or 0, into
BASIC's X and exit the program." Don't forget to end the program by
putting the lines:
Now, follow the instructions in Log 1 to
assemble, and try your program. Change the value of 'a' to anything, or
compare it with other numbers. Have a good ol' time!!!
Just a quick side note. When you are programming,
you might want to add notes to your program to tell yourself what you did,
or what each line does. This comes in handy when you are programming ENORMOUS
programs. All you have to do to make a note is put a semicolon ( ; ) before
the note on any line, and the assembler will not assemble it. Kind of like
ld a,5 ;Loads 5 into accumulator
Everything after the semicolon on the line
Remember, I already said that I'm NOT responsible
for ANY data loss on your TI- 83, so don't change these programs TOO much,
and nothing bad will happen (I hope). I typed this at 23:06 and I am tired,
so there are probably grammer mistakes galore. So sue me. If this log has
confused the hell out of you, read it again, or try reading the previous
logs again so you get a clue.
Thanks go out to the usuals, and Andy,
who published the document.
Thanks for your time, see you in vol. 4!