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Newsletter - April 1999

The ticalc.org Newsletter
http://www.ticalc.org/
April 1999 - Volume 2, Issue 4

IN THIS ISSUE

Letter from the Editor
Letter to the Editor
Calculator News
Programming in Assembly, Part II
Interview with Matt Johnson
Miscellany

LETTER FROM THE EDITOR

Thank you for reading the ticalc.org newsletter! The Program of the Month voting continues this month. Due to a lack of interest in last month's voting, the results will not count (only seven votes maximum were cast for each of the categories). This time we have posted the voting on the news so that more people will vote.

To see the programs which have been nominated and/or cast your vote for the best program in each category, go to http://www.ticalc.org/survey/potm/3.html. In order to vote you must be registered in our voting system. If you are not yet a registered voter on ticalc.org, please go to http://www.ticalc.org/survey/request.html before voting for the Program of the Month. The polls will remain open for one week, after which time the winners will be announced in an addendum to this newsletter.

Kirk Meyer


LETTER TO THE EDITOR

If you have anything that you would like to have published in this newsletter, please send it to newsletter@ticalc.org. Each month I will print one letter that I choose in the "Letter to the Editor" section. You can send letters regarding just about anything as long as they are constructive. Send your letters to the editor to newsletter@ticalc.org.


CALCULATOR NEWS

In calculator news this month, Icarus Productions has been active. Andreas Ess has released M.C. Mik #2 v1.0u, the sequel to the popular original, for Usgard. Additionally, Matt Shepcar has released Bomberbloke v0.96, with more features and levels.

Additionally, a great number of hosted sites have been added this month. It would not be fitting to list every single one here, however. For a complete list of our hosted sites, please visit http://www.ticalc.org/services/hosting/index.html for a complete listing of our hosted sites. For more information about our hosting program, email hosting@ticalc.org .

PROGRAMMING IN ASSEMBLY, PART II

This month I will continue on the topic of programming in assembly language. Last time I cleared up issues about variables and the stack. If you didn't catch last month's installment, check out the newsletter archives (refer to the Misce llany section). In this installment I will deal with the common instructions tha t are used in assembly language. I will again remind the reader that I will refe r to the Z80 whenever a specific reference is necessary.

Before doing tha t I will introduce the assembly version of equals, and for the Z80 that is LD. F or example, if you do 'LD A,4' then the register A now holds the value of 4. You may use this command for both single registers (such as A, B, and C) or for register pairs (such as BC, DE, and HL). More information about using this instruction will be presented in a later installment.

Note that for single registers, A is the primary register, and for register pairs, HL is the primary register. What this means is that the destination of most non-load operations (such as 'LD') must be either A or HL. For example, performing 'ADD B,A' is not legal because B cannot be the destination register for the result.

The first set of commonly used instructions are the math set. This includes the following instructions: ADD, ADC, CP, INC, DEC, SBC, and SUB. ADD takes the second argument, adds it to the first, and stores it in the first. For example, 'ADD A,4' will add four to whatever value A holds, and store the result in A. SUB takes the second argument and subtracts it from A, storing the result in A. This is the opposite of the ADD command. INC and DEC are just forms of ADD and SUB that perform A+=1 and A-=1 (respectively). We will deal with ADC, SBC, and CP in a later discussion after the flags have been introduced.

The next set of instructions are the boolean set. This includes the following instructions: AND, OR, XOR, BIT, RES, and SET. If you are unsure as to what AND, OR, and XOR do, set your TI calculator to Binary base mode and use the built-in 'and', 'or', and 'xor' functions to see what their effects are. RES resets a bit of a register. Bits are numbered as 7 being the left bit and 0 being the right bit. For example, if A equals %11110000 (the % sign indicates a binary number), then 'RES 6,A' would mean that A now equals %10110000. The effect of SET is the opposite of RES, which is to set the specified bit of the specified register. Finally, the BIT command is used for test purposes and will be discussed with the flags.


INTERVIEW WITH MATT JOHNSON

Email: matt@acz.org
Web URL: http://matt.acz.org/
ICQ UIN: 8342478

Interview Log
Kirk How old are you and what level of education do you have?
Optic I am 16 years old and am a Junior in Clearwater High School, Florida.
Kirk What do you plan to do after you graduate?
Optic Probably go to college; University of South Florida looks pretty nice.
Kirk What calculators do you own?
Optic TI-86 and TI-89.
Kirk Do you plan to buy any other calculators soon?
Optic If I feel so inclined. The HP calculators look pretty fun to toy around with also.
Kirk What do you use your calculator for most?
Optic My math homework, and showing my friends the cool stuff ACZ is working on.
Kirk When and how did you find out about the "TI Community" and when did you first visit ticalc.org?
Optic My brother found ticalc.org when he bought a TI-85. Soon after, I had some money to spend and I did a little research. At first I bought a TI-82, and then took it back like a day later and got a TI-86.
Kirk When did you first visit ticalc.org?
Optic About a year and a half ago.
Kirk What was the first program you ever wrote?
Optic My first program was a sound demo program I wrote for 86 central.
Kirk How did you learn to program in assembly language?
Optic I filled out the form for my free Z80 books, and printed out everything I could find on ticalc.org, and asked the Assembly 86 mailing list for a lot of help. Dan Eble was extremely helpful.
Kirk How did you convince Zilog to send you the Z80 documentation?
Optic To convince Zilog to give me the documentation, I filled out the form and said I might be using this information to build my own Z80 computer... and a bunch of other junk :)
Kirk Do you have an idol TI programmer?
Optic Pat Milheron. Most people just do this for fun, he does it for fun and makes money doing it. Can't beat that!
Kirk What projects are you working on now?
Optic Well, most of the stuff I have been doing lately is for the ACZ website. I haven't been doing much Z80 programming since me and David Phillips were working on a side-scroller. There are a lot of cool projects going on at ACZ, however.
Kirk What advice would you give to people wanting to learn to program in assembly?
Optic Buy a 2-liter of moutain dew and start reading. When you get tired of reading, program. Then repeat Step-1 :)
Kirk Aren't you part of an alliance, so to speak?
Optic I'm a member of ACZ. It is a really cool bunch of programmers, extremely talented. We might be going for a trip to six-flags during the summer.

MISCELLANY

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