Memory Left . . .
As you can gather from the above I have quite an interest in how much memory my program has used. I believe that in Extended Basic there is a command that allows you to do this but I've not saved enough money yet. One way round this is to find the largest array size that the TI will allow you to dimension and still run the program. The largest array size with no program seems to be 1812. e. g.
10 DIM M( 1812)
will run, but
10 DIM M(1812) 20 PRINT "I LOVE TEXAS"
will not. As your program grows in length then the maximum array size will decrease. I find that on average a line of Basic program reduces the array size by 3- 3. 5 depending on the type of program.
Assuming that we have 14K available to us this indicates that a numerical array element uses roughly 8 bytes. This seems about right to me as it means 7 bytes to store a 14 digit number (e. g. using 4 bits per digit) and one byte for sign and exponent (max 127).
Anyway the technicalities don't matter since to use this method all you have to do is find the largest array you can dimension subtract this from 1812 and divide the answer by 3.5. This is approximately how many more lines you can add to your program.
10 DIM M( 900) REST OF THE PROGRAM
Runs OK Memory left = 1812-900 = 912 Lines left = 912/ 3.5= 260.
Comments, Conclusions and a Cry for Help Printers . . . Would it be possible for TIHOME to approach someone like Amber printers to see if they could provide an interface to our machine. From the copy of Tidings I have just read it would seem that some of our members could supply the technical details. Machine-code . . . Is anyone interested in writing some articles on 9900 machine code. I was going to buy the Mini Memory until I found that it did not explain the machine code commands. Is there a book available or do you have to buy the Editor/ Assembler to find out.
New Software Companies
. . . I must agree with the comments made by others about the lack of enthusiasm by some dealers over the TI. One of the problems seems to be an apparent lack of cassette based software. A prospective buyer gets his copy of "Your Computer" and finds it full of software for Spectrum, BBC, etc., but no TI. Talking to my local dealer this seems to be the biggest put-off.
Anyway . . . I thought if no-one else is doing it why shouldn't I. This saw the birth of "Time Travels Inc" and eventually the first game (see below). My cry for help is for a small number of TI users to play test future games. Your fee will be a free game and a view of some of the rubbish I don't end up selling. If you fancy the game described below and would also like to play/ test future games write me a small note when you send off for "Squadron Leader". I would like to know what tape recorder you use and a little about your interest in computing so that I can select a broad spectrum of users. If I choose you I will return your money together with a free copy of the game and a short questionnaire to complete when you have played it. (Needless to say the next game will be an adventure game once I've fitted it into my Memory) . . . Bye.
To Tidings readers a 25% discount if you order now . . . Normal price -6, but at the moment it will only cost you -4-50 inc p& p. Send to: Time Travels Inc, nn mmmmow Way, wwwwwn STOKE Staffs xx15 0zz
Bits and Bytes and Bits and Bytes and Bits and Bytes
The past few months have been good ones for the publication of programs for our computer - so I thought a quick run-down of all recent listings would be useful . . .
Computer and Video Games October Issue:
Hungarian Squares Puzzle by Stephen Shaw
November Issue: Space Lasar by GM Programs
December Issue: Hungarian Hex by Stephen Shaw
January Issue: Target by R. Matthews
Personal Computing Today
October Issue: Blind Maze by Mike O'Regan
January Issue: Earth Attack by Peter Clisby
Personal Computer World
Teepee Textpro by Mike O'Regan
All the listings are games programs with the exception of Teepee Textpro which is a word processor which works with the TI Thermal Printer, but can be adapted for use with other printers.
All the programs are in TI Basic needing only the standard console with the exception of Target which is in Extended Basic.
As you can see, the pace of publication of new programs is sure hotting up, and I am reliably informed that in February's issue of C & VG there are going to be more programs for the 99/ 4A including one about Manchester's sewers?!
Of course the publication of these programs depends on YOU - so all you budding programmers get out there and get published!
### It might not have escaped the attention of many new owners that there is a sorry lack of software floating around for our machine in comparison to some others like the Spectrum, VIC, etc. Well, now good news!
For some time now Stephen Shaw, one of our longest standing members, has been encouraging people to write programs for him to distribute as well as importing some very good examples of what is available in the U. S. Stephen now has numerous programs on offer, so write to him for a list at NN Alsrryy Road, Stockport, Cheshire SK4 Z11.
Thankfully a few other software houses are now marketing programs for our machine and three that have recently come to my attention are: TX Software of Harlow, Essex; Apex Trading of Brighton; and Titan Programs of Corsham, Wiltshire. Also Gemini Marketing of Exmouth, Devon do an excellent range of software for businesses and are promising to expand into educational software.
[1999 update: Gemini and Titan never produced anything for the TI. Apex produced some simple programs but did not last too long. TX suffered the unfortunate loss of its owner before the programs were issued, although Mr Mathews widow did manage to get some copies out.]
Meanwhile, back in Texas, TI have brought out three new command modules Parsec, Chisholm Trail and Alpiner, all priced around $30 in the States but not yet available over here. They all sound pretty exciting, particularly Parsec which I understand has digitized speech (whatever that is!). TI say that they don't know when these will be available over here or what the price will be - so I have ordered Parsec from a dealer in the States - my first attempt at a personal import!
You have to watch TI very closely at times . . . at least in this country. Available now is the Logo language which is a beautiful, child appropriate computer language which is soon going to take over as the major computer language in our schools . . . BUT . . . over in the U. S. Logo 2 has come out which is a HUGE improvement on the original, but TI in this country are keeping quiet about it. When I enquired about Logo 2, TI told me that this was still being tested out in the States - come off it!
Don't try to unload your obsolete Logos on us - we weren't born yesterday! Give us the REAL THING! Fanfare of trumpets: . . . 99'er Magazine have at last gone monthly! The latest edition I have (November 1982) is up to the usual high standard with good programs for you to type into your machine together with helpful tips and news. One particularly fascinating article was how TI Extended Basic handles subprograms - that's right, not subroutines, but actually subprograms within a program together with some entertaining examples. It is pointed out that this is a unique system which is not available on other micros - and apparently the next cheapest system that uses subprograms is one that costs -40,000!
For all those of you who have not yet bought the Extended Basic command module, this is the most highly recommended expansion of your system. The price has dropped from GBP 100 in the summer to GBP 69 which is the price advertised by AB & C Computers in Tidings' last edition - by this edition it might even have come down further!
Happy computing, Arieh Yacobi.
A couple of observations which may help other users: When using Number Scramble (Oldies But Goodies by Texas Instruments) on my 4A, I found that the X key did not move the numbers as it should have done. It now works OK after changing:
3200 IF KEY= 3 THEN 3270 3210 MROW=-1 3270 MCOL=-1
A very cheap cassette recorder which works well with the 99/ 4A is the Jones CT 5101. I use the Sanyo Slim 3G which I am very pleased with, but I know some recorders (regardless of price/ quality) just refuse to work with the computer. I believe it has a lot to do with the response time of the Auto Level Control.
Help please - I have just received my first batch of programs from the software library (Paul Dicks must spend most of his spare time copying programs!). I have some problems which others may have solved:
015 STARFIGHTER - No control 009 LUNAR LANDER - Metering doesn't seem to do anything 058 BOMB RUN - Doesn't run, Extended Basic? Not indicated on software library list as E/ B, so beware.
Finally, I am willing to help any beginners in my area (Swindon) if I can but would add that I still have my "L" [Learner] plates up myself! Anyway, if you can't seem to get off the ground, ring me on Swindon 822639.
The TMS9900 is a 64-pin integrated circuit. It has 16 data input and output lines and 15 address lines. There are also memory control and interrupt lines. The address range available is 32K words, limited by the 15 address lines. The processor always generates word addresses, bytes are selected internally. There are no general purpose registers in the micro-processor.
It has only three registers. These are: 1. Program counter (PC) - Used to address the program instruction. The PC is incremented each time an instruction is executed, to the next instruction. An instruction may occupy 1 , 2 or 3 words of memory, the processor always steps on the correct amount.
2. Status register (ST) - This carries the results of arithmetic and logical operations. Bits in this register are set or reset to indicated arithmetic or logical comparisons. This register also carries the interrupt priority. If an interrupt of lower priority than set occurs, it is ignored. If an interrupt of higher priority occurs, it is serviced and the interrupt mask priority is set equal to this higher value.
3. Workspace pointer (WP) - As the chip has no general purpose registers, a block of 16 words in memory is pointed to by the workspace pointer. These 16 words are then treated as 16 registers.
Example. If workspace pointer = >F800 (> means hexadecimal) and instruction MOV R0,R1 was executed, then this would write the contents of address >F800 into >F802. (Note all addresses are word addresses and thus even). The most significant byte of a word lives at the even address, the least significant byte lives at an odd address. So R0 is the byte at >F800 and the byte at >F801 , making R1 carry on at >F802.
This WP system means that a new set of 16 registers can be obtained at any time by changing the workspace pointer. If an interrupt occurs, then there is no need to save any registers. The PC, WP and ST are stored in registers 13, 14, and 15 of the new workspace, so that they can be restored at the end of the interrupt.
The 9900 has all it's 16 interrupt vectors (WP + PC addresses) stored in memory, locations 0000 -> 003E. After that come the 16 software interrupt XOP (Ext. Operations) resides at >FFFC, >FFFE. Thus it is normal to place ROM in locations 0-> 3E, so that RESET (level 0 interrupt, usually derived from power up) causes a trap to locations 0000 (for WP) and 0002 (for PC). The other way of getting the processor running is to put ROM at the top of memory and use the LOAD signal (RESET inhibited). The program can then set up the interrupt vectors in RAM at the bottom of memory.
So, the 99/ 4A must have ROM in main memory to enable the system to run from cold. I assume the Basic interpreter also lives there. There must also be some RAM for workspace use (the 1/ 4K I suppose). The 16K RAM is said to be connected to the VDP. I don't have a full data sheet on the 9918 so do not know much about it.
The next question is how the CPU communicates with the VDP. It could be that the VDP is mapped into main memory or it could be done through the CRU. The CRU is the Communications Register Unit. This grand sounding facility is actually a bit serial I/ O method. It works by setting an address on the address lines A4 to A14. The address is obtained from Register 12 of the current workspace. To do an input, the CPU samples the CRUIN line.
For an output, the CRUOUT line is set to 0 or 1, and required, followed by a pulse on the CRUCLK line. This can be done for single bit inputs and outputs or multiple (1-16) inputs and outputs. For multiple bit transfers, the address is changed for each bit. This system allows the micro to address 4096 input and output bits.
This system need not be used only for I/ O. RAM can be connected to the CRU address space and then written and read via CRU instructions. The advantage of CRU I/ O is the simplicity of the hardware. The disadvantage is the speed. An output of 16 bits (LDCR R1,0) takes 52 clock cycles (17.3ms at 3MHz clock). An input of 16 bits (STCR R1,0) takes 60 clock cycles (20ms). So if the VDP is CRU addressed, transfers to the RAM will be slow. (A memory mapped I/ 0, MOV R1,@ PORT is 22 clock cycles - 7ms).
Well, that's a brief tour of the TMS9900. In the TI-99/ 4A free glossy, under specifications it says "System memory and address signals available at peripheral connector". They may be, but if TI don't say what is on which pin, what use is it? Even if it cannot be included in the price, a hardware manual for a few pounds would be useful.
P. S. I don't have Mini Memory but if anyone has a question on 9900 assembly language, drop me a line.
Imagine! You wake at 7 a. m. one morning. There is a dull ache in your chest, your arms feel heavy as lead, your hands are tingling. You know you have a digestion like a horse, you've never had indigestion before, but the ache goes on and on and you cannot get back to sleep. You take a deep breath but the ache gets neither better nor worse. You feel as if you will never move again, heavy, washed out.
Suddenly you realize what is happening to you. All the lectures you have attended, all the folks you have talked to in hospital, all the books you have read come flooding back to you.
It is a heart attack! "Jen? You awake?" She turns over and groans. "I'm having a heart attack." She wakes up. Now there are advantages and disadvantages in having a nurse as a wife. They have a way of dismissing aches and paints as malingering. But this time in one minute flat she had run through the traditional list of symptoms. In one minute ten seconds you are sitting up at a forty five degree angle supported by pillows. One minute twenty and she is on the telephone to the G. P. (General Practitioner = doctor). Two minutes and she is packing "a few things" into a case ready for when the ambulance comes after her diagnosis has been confirmed by the doctor.
That is how my break through started. A few weeks in hospital which were busy and interesting and then home. Then I began to realize just how long a day really was. And the days stretched away in one long unbroken chain. What was I going to do with all that time?
I had been enjoying a full and satisfying life style. I had been a Methodist Minister for 26 years. I was looking after five churches with all the fun and sadness that goes with being involved in the devotional and social life of so many people. I had been doing a bit of teaching, just Psychology and Religious Studies at the local District College. I was Free Church Chaplain to a local Psychiatric Hospital. I was studying part time for a Masters degree with Sheffield University, and keeping up with my favorite hobby of astronomy.
How long before I could begin picking up my life again? Six months, they said, at least. Nothing intellectually demanding, they said. You'll have to give something up, they said, and get some weight off.
About this time, among the other magazines, someone sent me a copy of Printout. It was full of a jargon I didn't understand, though I'd done a bit of computing with an Open University course back in 1973. I found I only understood one word in ten. So I got them to bring me more computing magazines and soon
I had decided I was going to buy a micro. I listed all the attributes of my ideal micro. The two real one's which came anywhere near my ideal were the BBC 'B' and the TI-99/ 4A. But I found I would have to wait at least six months for a BBC so I ordered a Texas from Computer Supermarket in Corby with an Extended Basic module. Within a week it came.
Up till now I have spent my days reading. I'd always intended to read the vet books by James Herriott, now I read them one a day. I discovered the Covenant books by Stephen Donaldson: they took a little longer to read. I read the only one of Richard Adam's books I hadn't already read, Plague Dogs but suddenly I had no time for reading, the days sped by. I had found a new type of therapy.
My wife named it Texas Therapy. A new way to recover from a coronary. But there is still my break-through to tell you about.
One of the after effects of my heart attack is a new kind of pain in my chest. I get it under two sets of conditions (i) when I get excited (ii) when the wind blows in my face. The pain is called angina.
I can play a lot of TI Invaders before the excitement brings on my chest pain. But I first noticed that computer games do bring on angina after buying Octal from Stephen Shaw. Then I found that when I reached the third floor of Keys To The Castle (also obtainable from Stephen) I began to suffer. But the game which has given me the worst bout of angina is The Attack. After about one minute at level two I feel the ache begin and after five minutes I can stand it no longer and have to give up.
They say Parsec is even more exciting. Well, I will tell you. I have ordered it and we will see how it does on my new rating scale, how long it takes to give me angina.
These are my ratings so far:
TI Invaders 20+ Keys to the Castle 15 Octal 10 Cross Country Car Rally 7 Winging it 4 (lt comes on as a crash, and I always do). The Attack 1
The smaller the number, the quicker my angina starts and therefore the more exciting the game is. And that gives me an idea. There might be a way of raising enough money to buy myself a disk system in this heart of mine.
So Software House please note: If you want an independent objective assessment of how exciting your new game is why not try it out on my heart? Say GBP 5 a time? Let me see . . . that will be about 100 evaluations! I wonder if my heart will stand it?
by Cyril D. Blount.
Does your micro produce numbers which are consistently random when you call RND and tell it to RANDOMIZE or does it give you numbers whose distribution contain an inherent pattern? Why not check it out? Let us set our computer to generate pairs of digits in the range 0 to 9. If the two numbers generated are the same we score a "hit". In a run of 10,000 pairs we would expect a random number generator to produce 1,000 hits in theory, but on my 99/ 4A I scored 113 hits too many.
Superficially this shows that the TI Pseudo Random Number Generator does not produce random numbers, but if such results are obtained consistently with different computers using different methods of random number generation, and also when using such random natural events as radioactive decay to generate random numbers, then you need to ask what randomness is.
So I recommend a book to set you thinking and to stimulate you to perform experiments in randomness on your TI-99/ 4A. On Time by Michael Shallis (sub-titled, "An Investigation into Scientific Knowledge and Human Experience"). Published by Burnett Books Ltd., 1982.
I too wasted my day by going to the Northern Computer Fair at Belle Vue last December. Why doesn't TI exhibit at these do's? However I came away with one thing worth passing on. I had always kept my console covered with a piece of cloth thinking to keep dust and dog's hairs out of it. But while I was at the Fair I ordered a cover for my console. It cost me -4 and I am very satisfied with it. It fits very neatly and is well finished. I got it from Micro Aids, 2 Boston Close, Culcheth, Warrington, WA3 4LW. Their telephone number is 092 576 2804.
I have just received the newsletter of the International 99/ 4 Users-Group dated November 15, 1982. For those who have bought themselves a Mini Memory module there is an excellent article in it on the Assembly Language blues, and a report promising TI's version of Forth in the first quarter of 1983. Some time ago I bought an assembly source listing for Fig Forth 9900 from Microprocessor Engineering Ltd. of Southampton with the thought I would adapt it for the 99/ 4A. But it was beyond me, so I look forward to TI's own module. The annual subscription for the International Users-Group newsletter is $12 and membership offers a number of discounts on TI products. The address of the group is PO Box nn, Bethany, OK 73nnn, USA.
Oaktree Systems of 3922 Valentine Road, Whitmore Lake, MI 48189, USA have a package on offer for $24.95 for display enhancement. They offer a 40-character wide display mode instead of the 28-character standard display, plus forward and backward scrolling of 96 lines and the ability to split the screen into two parts so that one is scrolled while the other is stationary. However you will need Memory Expansion, Extended BASIC and Disk Drive to run it. It works by using 6 by 8 pixels to define the characters instead of 8 by 8 pixels and it occupies 3842 bytes of memory space.
If you are a Minister or Member of a Church you may be thinking about how you can use your micro for the benefit of your parish or circuit. You are not alone. The CCUG (Church Computer User's Group) has been set up by a group of enthusiasts to "gather and share ideas and information about the use of Computers in Church".
The Rev. R. S. Wilson of Ggggnside Vicarage, Rrron, Tyne and Wear is the editor of the magazine Church Computer and the Rev. Nigel Hardcastle of nnn Rrrrrrfield Road, Ggggetts Green, Birmingham deals with everything else.
In the December edition of the magazine there are articles on filing, computers and privacy, finance, religious education, computerization of diocesan offices and a report of the Church of England working party on computers.
Finally a little program for you to play with. It uses a simple FOR-NEXT loop as a clock.
100 INPUT "WHAT IS THE PRESENT TIME, IN HOURS, MINUTES?": Z, Y 110 X= 0 120 FOR TIME= 1 TO 309 130 NEXT TIME 140 X= X+ 1 150 IF X< 60 THEN 120 160 Y= Y+ 1 170 CALL CLEAR 180 PRINT Z;" HOURS", Y;" MINUTES" 190 IF Y= 60 THEN 200 ELSE 230 200 Y= 0 210 Z= Z+ 1 220 IF Z= 24 THEN Z= 0 230 IF X= 60 THEN 110
If you are using Extended BASIC then the loop runs at a different rate and line 120 needs to be changed to:
120 FOR TIME= 1 TO 227
HOLD over: resume processing.
Dear Paul, I would be very pleased to have my name published in Tidings for anyone who is interested in educational software for Primary Remedial or Special Education.
I am still pursuing my research into the possibility of acquiring LOGO without an exorbitant expenditure. I was discouraged at one point, by a contact who told me that it would be very difficult and would require a lot of effort on my part without any backup available. At that point I almost decided to trade in my TI for a micro with a cheaper expansion system. However, a fortnight ago in The Times Educational Supplement (12. 11. 82) there was an article giving a reference to a Rhys Gwyn in Didsbury School of Education, Manchester Polytechnic who has been experimenting with TI Logo in Primary Schools. I phoned him, and he reassured me about the possibility of using the module without difficulty. He is also going to send me details of a summer school on Logo, which I may decide to attend. So, with new enthusiasm I may indeed acquire the expansion system, 32K card and module, all to be able to key in
TELL SPRITE CARRY: TRUCK SET COLOR :RED SET HEADING :EAST SETSPEED 100
and see a little truck dash. across the monitor, on which I will previously have drawn a suitable background.
If it ever comes about, I will write you an article for Tidings! Many thanks for all the effort you put into TIHOME, and happy computing.