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TI-User was a small magazine published by Galaxy in Maidstone, a small retailer, aimed to support their customers with Texas Instruments TI99/4a Home Computers - with creative input from Lantern Software. The content is valid for users of the TI99/4a emulations including MESS. This is the fourth issue of their magazine, with a cover date of May 1984.
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TI USER 4 - MAY 1984


Comment The largest problem posed by TI’s withdrawal from the home computer market is that the cartridge software once abundantly availble from many shops is now very hard to find. This would appear to make owning a TI 99/4A look a bit like owning a cassette recorder without any cassettes. The big difference lies in the fact that you can create programs on a computer.

What you have to ask yourself is 'what can I do with my computer' and the answer to that question really lies in what you want to get out of it. If you want to do nothing but play cartridge-style games or if you want to add memory expansion, disk drives and modems then you will probably be better off looking for another machine. If, however, you are interested in learning about computers, how they work, how to write programs and if you are prepared to do bit of looking around for information and software then you should find that the TEXAS will do everything you want it to.

Don't forget, the TI 99/4A is probably the best computer there is for learning how to write programs, the BASIC is very clear and powerful compared to some other machines.

If you want games there are many third party software houses who advertise regularly in the popular computer magazines. What makes computers fun though is not just the games but their flexibility. Try and think of all the things you use your computer for now, apart from games... not very many I’m sure! If you spend a little time thinking about it you will begin to discover that computers could do a lot more for you. Use your imagination! How about getting your TI to: Help with homework, keep track of your money, keep a list of all your records and tapes, make a list of your timetables (school, exams, work etc), these are all things your computer could do either by a small amount of programming or by buying software that will do it for you.

BOOKS THE SMART PROGRAMMING GUIDE FOR SPRITES

If you have the Extended Basic cartridge and are interested in using the sprite graphics to their full, then this is the book for you. Within its pages you will find detailed explanations of just about every use you can think of for sprites. Some chapter headings are:

Sprite Patterns, sprite chase, Shooting sprites, Pick up objects. Eat dots and lay down trail, etc.

Each new subject is handled clearly, with example programs (all those I typed in were bug free), and step by step explanations of how the program is doing what it is doing. The author is obviously very familiar with the operating system of the TI 99/4A and with the operations of BASIC since tips on how to speed up your programs and useful insights into the machine are liberally scattered through the book.

For those who have not yet discovered the delights of Peeking and Poking let me explain that the PEEK command in Extended Basic allows you to look directly into what is called the CPU RAM.

By looking directly at what is stored in this section of memory with CALL PEEK we have a very fast way of bypassing such slow basic operations as creating random numbers.

If all this is beyond you, don't worry, CALL PEEK covers only a small section of this interesting and useful book and I would strongly recommend it to anyone wishing to get more from their Extended Basic.

[sjs 2016- book available online.]


INITIATION INTO THE TI-99/4A ASSEMBLY LANGUAGE with the "mini-memory"

Is this the book that will satisfy all those mini-memory owning potential assembly language programmers? Well, it just may be at that.

The greatest problem in trying to teach aseembly language is the language and jargon is so very different from that of the BASIC programming environment.

Words such as Registers, Workspace, Operands and Mnemonics are just some of the terms which require clarification at a very early stage. To a small extent this book does make an attempt to explain such terms as they arise however, you do still find yourself presented with a host of unfamiliar terms at a very early stage. This is probably the boooks major shortcoming.

The rest of what I have to say of this publication is, thankfully, all good.

The reader is taken methodically through the various numbering systems, the features of EASY BUG, and the rudiments of using the Line-by-Line Assembler.

There are many example programs with detailed explanations, and all those we entered were bug free.

One of the things I liked most about the book was that it assumed the reader would experience some difficulty at first and even advises you to leave out some chapters until later or to go back and read certain chapters if you are having difficulty. Assembly language is bound to be a bit difficult at first but with his system of reading chapters when they are required you tend not to get as bogged down as you would with other publications.

Compared to the Editor/Assembler manual this book is a joy. I would, however, state that in my opinion there is no escaping the need for the E/A manual for the serious programmer.

All in all this is a usesful book: with some delightful assembly language programs such as thoae which allow you to draw on the screen in the high resolution BIT MAP MODE (not available in BASIC) and in the MULTICOLOUR MODE (also not available from BASIC).

The best tutorial yet for the potential assembly language programmer

[2016- This was a French book by Denise Amrouche and Roger Didi which can sometimes be found on ebay but has no online presence].

MODULES There is now no doubt that EMI have decided not to release the cartridge games they had planned for the TI, which is a great pity since, having seen them in action, in my opinion they would have represented some of the best software available for the computer.
[2016 sjs: It took a couple more years but Howard Greenburg of Arcade Hardware was finally able to arrange for three Thorne-EMI titles to be released for the TI99/4a]

There are, however, some new modules about if you’re prepared to hunt for them and the ATARISOFT range is now being actively marketed by ATARI. In spite of representing a high standard of programming on some of the range, such as the excellent versions of Donkey Kong and Defender, these modules have caused some problems for a few TI-99/4a owners.

The plastic casings on some of the cartridqes have been prone to wobble a bit in the cartridge slot and for one or two unfortunate owners the modules have been found not to operate at all. I would stress that this is not really a fault of the cartridges but stems from Texas Instruments resolve to stop other companies producing games for their machine. In the later models of the TI-99/4a, the VERSION 2.2, TI have altered the circuitry so that only their own cartridges can use the port. So be warned, non-TI modules will not run on your machine if you have a version 2.2 computer. The version you have is written on the test card which appears when you first switch on the machine.

[2016-sjs- Some of the Atarisoft modules used the console's built in large character set that appears on the opening test card screen. They used a direct address which TI changed in some consoles, resulting in corrupted text in the games. There was no fix]

Apart from these problems, which affect only a minority of users, most of the Atarisoft games are great fun. If you haven't seen their Donkey Kong I would recommend it.

STOP PRESS - At the time of going to press the Atarisoft range is unavailable in the U.K


Now, what of those new modules I was speaking of earlier? Well, these really are new games, from both TI themselves and from well known games companies such as IMAGIC and SEGA. As I mentioned these games are not due for general release and are only available from two sources that I am aware of and these companies have only imported limited numbers at their own expense. If you want to find out more about these products then I would advise that you either telephone or wite to either: ARCADE HARDWARE or PARCO ELECTRICS

Titles. that I can remember are; Moonmine, Hopper, MASH, Slymoids, Space Bandit. Sewermania, Bigfoot, Superfly, Jawbreaker, Microsurgeon, Burgertime and Buck Rogers and the planet of Zoom. The last title is the only one I am very familiar with and can recommend it as an excellent game with superb 3d graphics. Other titles that are reputed to be of a high standard are MASH, Microsurgeon and Burgertime

IUG INTERNATIONAL USERS GROUP

Now that the TI is no longer in production it is becoming more and more important for TI owners to club toqether and communicate, to swap programs and ideas and to learn from each other. Specialist publications such as "99'er Magazine" specifically coverinq the TI-99/4A have always in the past been a boon to those of us who wish to get the most from our computer", Sadly, 99er magazine has withdrawn its excellent coverage and is now diversifying in order to stay competative, a departure which, I’m sure, leaves many TI-Users high and dry when it comes to their need for software and tutorial articles.

You may remember my mentioning in one of the earlier issues a group called the The International 99/4 Users Group, since that issue I have subscribed to the group and I am now very glad that I did. The group offers a monthly newsletter and a bi-monthly colour magazine called Enthusiast 99, a publication which rivals 99er for its programming ideas and software. The magazine deals with all facets of the TI and has its ear to the ground as far as computer news is concerned, articles cover everything from the very simplest basic programs to the most complex machine code ideas and information, all presented in a very sophisticated format.

As if this were not enough the group also offers a software market and exchange scheme, open to members only, with a selection of over two thousand software titles!

I would heartily recommend this magazine and user club since it offers very good professiona1 support and an access to software on the American market both cheaply and under the guarantee of the I.U.G

INTERNATIONAL 99/4 USERS GROUP BETHANY

[2016- Unfortunate timing this little article. The last issue of Enthusiast 99 produced by the IUG was May-June 1984. Ultimately it was wound up insolvent. There were issues about unmet subscriptions and other unfortunate matters.]

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TIPS TI-TIPS

What can you do with CALL KEY? How can you use it to best effect?

Let's start by examining what it does and then perhaps we will be able to find one or two new uses for it. Take the statement:
100 CALL KEY (0,K,S)
100 is the program line number, CALL KEY tells the computer that it should prepare to scan the keyboard to see whether or not a key has been pressed.

Inside the brackets, the 0 tells the computer exactly what type of scan to perform - this is important and is something many people ignore. 0 is most often used simply because it is given as the main example in the reference book, what it does is cause the computer to return the ASCII code (see pages 93 and 102 of the Users Reference Guide) for the key pressed and assign it to the variable K. So that if you were pressing the D key when line 100 was executed, the variable K would equal 68. If no key is pressed then K=-1. The variable S in line 100 will equal 0 if no key has been pressed, -1 if a key has been pressed and +1 if a key has been pressed that was different to that of the last keyboard scan.
The following short program will allow the user to press any key and see what values are returned for K

100 CALL CLEAR
110 CALL KEY (0,K,S)
120 PRINT K
130 GOTO 110

Try pressing keys with the alpha lock up and with it down, also use the function and control keys. when you are familiar with the kind of response you get and have looked at page 90 of the reference guide, alter the number in the brackets of line 110 to another number less than 6. Page 90 gives a rough explanation of the different numbers the keys will return.

Probably the most useful number to use is 3. This disables the entry of lower case characters (not their use in a program) so that whether the alpha lock is up or down you wi11 still only get the ASCII codes for capital letters. How many times have you seen Play with the alpha lock down on your screen?

Codes 1 and 2 split the keyboard and the numbers returned are shown on page 91 of the |reference guide, these codes also read the fire buttons of the two joysticks - K will equal 18 if a button has been pressed.

On page 93 of the reference guide the table of function keys and control keys show the values returned when these keys are used. The control key table should be useful to those wishing to make use of the graphics capabilities of the control keys as outlined in the first issue of TI-USER.

-------
How do you use random numbers to their best effect?

There are two Basic commands related to the generation of random numbers, they are RANDOMIZE and RND.

RND is concerned with creating a random number whilst RANDOMIZE allows you to specify the type of number you want and to control the RND command. Here’s how it works.
100 CALL CLEAR
110 PRINT RND
120 GOTO 110

what you get is a series of numbers greater than or equal to zero but less than a one. If you run the program again though you will get exactly the same series of number, not very random!

This is where the RANDOMIZE statement comes in. If you add the line
50 RANDOMIZE
you will now get a different set of numbers every time the program is run.

You can further control the RND command by using what is called a seed with the RANDOMIZE command. what this does is to give you a sequence of numbers that is repeatable
eg. Alter line 50 to the following
50 RANDOMIZE 81

Once more you will get the same sequence of numbers every time you run the program. A different seed will produce a different sequence and each sequence is repeatable just by using the appropriate seed. Take note not to use more than two figure numbers since the computer only uses the first two bytes of the number.

Now, after all that, how do you get a truly random number between say, 1 and 255? Well, let's start by adding 1 to the value of RND, this gets us a number between 1 and 2.9999999r. If we then multiply that by 255 and use INT to get a whole number we end up in the right place

100 CALL CLEAR
110 RANDOMIZE
120 R=INT(RND*255)+1
130 PRINT R
140 GOTO 120

Generally speaking, you can use the following formula to get the range of random numbers you require:
H=The highest random number required
L=The lowest random number required
R=INT(RND*(H-L))+L
There are quicker ways of generating random numbers with Extended Basic, by Peeking the scratch pad ram - for a detailed explanation see the Smart Programming Guide for Sprites- review this issue.

Module Review Review
BUCK ROGERS Planet of Zoom
As far as home computer games rate, this game has to be a ten out of ten.
You are preseanted with a landscape in 3D, you can see your ship from above whilst the multi-coloured landscape rolls towards you and an onboard computerized voice says "avoid the electron towers Buck". This is easier said than done but try telling that to a speech synthesiser. Nevertheless; you push the joystick forward and guide your ship between the narrow towers.

Suddenly you have gone far enough and the warning comes "watch the Hoppers".
Hoppers are nasty! You can see them in the dietance- steeadily hoppinq towards you, getting larger as they approach. Some spring at you from the side and some sandwhich you between the electron towers, you need all your wits about you and eyes everywhere! When you've ploughed your way through the hoppers you race off into space where you hear "alien guard approaching". These are a swarm saucers which swoop and dive at you, once you have beaten them off their mother ship arrives - the mother- ship comes at you and is very large - when you have destroyed this then you move to a harder level and try again.

One thing I really liked about this game was the control you have over the level of difficulty involved. Speed is the essential factor here - the faster you go the harder it gets and the more points you score. Unusually, if you travel fast, you actually use up less fuel which gives you another incentive to try it the hard way.

I really enjoyed this game, the graphics were good and the actiion frenzied at times, skillful at others. The addition of speech adds another dimension to the game which is lacking on many other computers

[Each to his own- I very quickly found this module pointless and boring-sjs]

PRODUCT NEWS
LANTERN SOFTWARE have just released their first all machine code game for the mini-memory module, believed to be the first machine code game to be designed and written for the mini-memory by a UK software house.
The game, occupying the full 4k is called SNEAKIES and currently retails at GBP6.95

The scenario finds you on a deserted grass plain with volcanoes erupting in the distance. The Creakies are little alien figures who jump from brightly coloured balloons drifting across the skies. Their plan is to disguide their invasion. It is therefore up to you to shoot and burst the balloons with your laser tank, fire at the protective mother ship medning the balloons as fast as you burst them and to catch all the falling sneakies before they hit the ground or the open bay of the tank - no easy task.

As you get farther into the game it speeds up to breakneck proportions and you will certainly find yourself with a problem on your hands.

Mini Memory Assembly MINI -MEMORY
In attempting to give some kind of ongoing tutorial on assembly language and the use of the mini-memory it would be firuitless to start right at the beginning since it would require a fairly lengthy book to handle that and with the magazine being quarterly we wouldnt get very far very quickly.

What I propose to do is to use example programs to give as much insight as possible into the operation of asssembly language and the internal layout of the TI-99/4a

A good place to start is probably with accessing the screen and printing characters on it. First ffom basic, using the new commands PEEK and POKE and then with assembly language. I would advise, though that you have handy either a copy of the Editor/Assembler manual or preferably of "Initiation into TI-99/4a Assembly Language".

Imagine computer memory as a series of cardboard boxes- they can either be empty or they can contain a number. The largest number that any one box can hold is 255 and the loweat 0. Each box is numbered so that it is locatable, the first 0 then 1, then 2, etc these reference numbers are called memory addresses and with the Basic commands PEEK and POKE you can give the computer an address and either peek at the number at that location or poke a number into a box at that location.

Your screen is split up into 24 rows by 32 columns and it is not hard to visualise the screen grid, with each letter being placed in one location of this grid. Imagine instead that each location on the screen has a memory address instead of a grid reference so that the top left position on the screen is now at address zero in memory, the next location across is at address two, the next at three etc. until you reach address 31 at the right edge of the screen. The next location is address 32 and is one row down on fhe 1eft side of the screen
00,01,02,03,04,05,06 .....31
32,33,34,35,36,37,38 ......63
etc

This is in fact how the VDP RAM is arranged. The screen is made up of a block of memory boxes starting at location 0 and ending at location 767. This is what is shown on the memory map on page 76 of the mini-memory manual OK, so what can we do now that we know all this? Well the computer thinks that the screen starts at VDP address 0 so that if you were to POKE a number into any VDP address between 0 and 767 then a character will be placed on the screen. In order to print a character that can be seen you will have to select a number from the legal range of ASCII codes and then add 96. So to POKE an A onto the screen you would use 65+96=161. When you are working from Basic you will always have to add this offset of 96

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So the command CALL PEEK(367,x) will perform an operation similar to that of GCHAR, fetching a character code from address 367 om the screen. CALL POKEV(367,161) will print an A in the centre of the screen. The big advantage of this method is that it is much faster than the usual basic commands and that you can Peek and Poke successive bytes in one command eg
CALL POKEV(365,72+96,69+96,7
6+96,79+96,79+96)

This prints ’HELLO’ very quickly in the middle of the screen. Here then is an excellent way of speeding up your Basic programs
Now, lets have a look at the short assembly language routine that I gave you to look at last issue. what this did, if you were one of those who managed to make it work, was to print the words P'RINT THIS LINE on the screen and it worked in a similar fashion to the basic line above.

Here is the program listing. Remember to type a space whenever the ’sp’ appears

    
    sp AORG sp  >7D00
T1  sp TEXT sp  'PRINT THIS LINE'
    sp LI   sp  R0,>0126
    sp LI   sp  R1,T1
    sp LI   sp  R2,15
    sp BLWP sp  @>6028
L1  sp LIMI sp  2
    sp LIMI sp  0
    sp JMP  sp  L1
    sp  END

You will see the hexadecimal numbers and addresses qiven by the assembler.
In order to see this program in action you should load the Line-by-Line Assembler via the 'L' option of the EASY BUG, quit the easy bug and select minimemory RUN, using a program name NEW

Let's examine what this program is doing.
The Assembler commands are listed in both of the manuals previously mentioned.
In line 1, AORG stands for Absolute ORiGine and it tells the assembler (which is the program you loaded and which you are usinq to enter the assembly language program) where in the 4k of CPU memory to place the first machine code instructions.

Now the assembler program is actually taking up much of the 4k so that you have about 1k of programming space left. Hex address >7D00 is at about the starting point of the free section of memory.

Line 2 is rather like the DATA command of Basic, only TEXT converts each letter into its ASCII equivalent and places it in memory. T1 is a label and is simply there so that you are able to locate the Start of the text.

In line 3 we are loading a hexadecimal number into what is called a REGISTER. You can use 16 registers at any one time, each represents two bytes in a 32 byte section of memory called a WORKSPACE. These registers are numbered R1,R2,R3 etc and are used in assembly language in a similar manner to variables in basic.

The actual command in this line reads 'Load Immediate Register 0 with the hex. number >0126' What we are doing is storing the screen address where the first byte of TEXT will be printed. Hex >0126 is equal to decimal 294.

Line 4 loads the start address in CPU RAM of the first byte of TEXT into Register 1. When we created the label T1, the assembler automatically made the label T1 equal to the address at which the data starts. Again the usage of labels is similar to that of variables.

Line 5 loads the number of bytes that will be read from CPU RAM onto the screen, in other words the number of letters and spaces in the 'PRINT THIS LINE' ie fifteen. You will notice that the assembler understands decimal 15 as 15 and does not attempt to read it in hexadecimal because it is not preceded by a greater than sign (> ). Either system of numbering is acceptable but it is essential to become familiar with hex as early as you can.

Line 6 is like Basic GOSUB. Having stored in the registers all the information you need to transfer data from CPU memory to the screen in VDP memory, we can now Branch to a utility routine in the mini-memory which will do the the transfer work for us.

This routine uses a different set of registers to our own so we are using the command Branch and Load Workspace Pointer (BLWP) location >6028 the routine will find two address, one will be the start of the utility routine, the other will be the address in memory of the new workspace ie the utility program's set of variables. When the utility routine has finished it then returns to your program to execute the next line.

Lines 7 and 8 are beyond the scope of this article, their function is to allow the prgram to be quitted - otherwise you would have to switch off to stop the program running. L1 is a label similar to T1 and in Line 9 it is used to tell the program where to jump back to. The command JMP acts like the Basic GOTO.

So there it is we have used the machine code utility routine called VDP Mu1tiple Byte Write described in the Mini-Memory manual on page 35

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