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     PC99 Review

TIHOME Tidings August 1982 - Volume 2 Number 4, whole series number 10.

Jump to: Rambles article start   ||   A program that rewrites itself  ||  Graphics Mode 3   ||   Range and accuracy of Call Sound
Using a Personal Record Keeping database with TI Basic   ||   Using a PRK datafile to hold array values ||   Faster Banthorpe Plot

Pete Brooks wrote:
I stated that the TE II could NOT speak listings. At the time of writing, to the best of my knowledge that was true; however, Mike O'Regan's friend, Les Ball, had contacted Stephen Fung who in turn had contacted me, to tell me that although the TE II manuals say nowt about it, the TE II CAN speak listings, BUT, and here's the catch, it CAN'T speak ALL of the listing.
Any punctuation marks which correspond to "pause" commands are not spoken (could be a problem in PRINT, INPUT, DISPLAY, etc.) and there may be other minor difficulties.
Apparently all that TE II owners need to do is to LIST to the Speech Synthesiser as if it were a peripheral like the Thermal Printer. Under TE II, speech is output by opening a file to the synthesiser and then PRINTing to it. I do not have the exact commands to hand at present, but the format will be: LIST "speech file instructions" : line numbers if required.
From Robin Frowd Product Manager Texas Instruments Ltd. :
Well, I think I have recovered from the rigours, feet-ache and reduction in my word store as a result of the PCW Show held at the Barbican Centre on September 9-12. The Exhibition was a resounding success and I understand that approximately six times more people came to this years show as last year, and I am convinced I talked to each individual visitor.
I met a number of the members of TIHOME during the Exhibition including those well known contributors to TIHOME, Peter Brooks, Mike O'Regan and Stephen Shaw, as well as a gentleman by the name of Paul Dicks.

The reaction of the visitors to the Texas Instruments stand was very good and we had to get one of our London dealers to sell from the stand due to the demand. We had many compliments about the TI stand and at many times during the Exhibition they were queueing four deep to get at the computers. Consequently we will be at the show next year, but with a much bigger stand.

For us, one of the biggest bonuses from the Exhibition was the many contacts we made with third-party software companies who were eager to write and market software for the TI-99/4A. All these contacts will be followed up and you can look forward to many additional sources to purchase software of all types. It was surprising how many of these companies had not contacted us because they felt awkward in talking to a very large multinational corporation. Well we really are friendly people and want to talk to anyone who has really good ideas and even better software packages.

I have had some compliments recently about availability of TI Software. Its the old story about the local stockist not having the particular package you require. We are currently working on a Nationwide mail order set-up to allow people to order any currently marketed TI Software Package from a source which stocks the whole range.

I am aware of one problem, however, concerning Terminal Emulator II and Text-to-Speech. We have been asked if the computer will "speak" a program listing, it will and the input to achieve this is
Remember a space is need between LIST and the open quote marks. This particular command is an example of how subtle we at Texas Instruments can be - we did not put it in the manual.

Mini Memory, Logo. Editor/Assembler and the Peripheral Expansion System will all be available this month, the TI-99/4A and software are all now freely available and next month comes some new games like Alpiner, Othello, and Chisholm, as well as UCSD Pascal.
Sales of the TI-99/4A are going very well and extra distribution is being added all the time.

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Handling PRK files with Enhanced Basic

by Franc Grootjen and Paul Karis Blxxxgras 2. 39NN AA Veenendaal, The Netherlands
(The TI booklet describing extra calls available in Basic when the PRK or Stats modules were inserted is available online as a PDF file from )

Owners of the Personal Record Keeping (PRK) module will have discovered the many advantages of this useful pre-programmed file handling system. Some may have even heard about an interaction with TI Basic to INPUT or PRINT anywhere on the screen with CALL A and CALL D respectively

Aptly christened Enhanced Basic

Few will have heard of the further features of Enhanced Basic enabling the user:
a. To change any characteristic of once chosen pages without losing all the entered data.
b. To perform mutations upon PRK data which are not possible with the PRK options.
c. To use two independent memory systems side by side and in conjunction.
d. To perform string operations on PRK data.
e. To save long arrays quickly without problems.
I am driving at the use of the statements:
CALL P .... CALL L .... CALL S .... CALL G .... CALL H

CALL P(N) - Partition
In order to prepare or partition the RAM memory space in two sections the statement CALL P(N) has to be entered in the immediate mode as a first action after the TI BASIC READY prompt from the computer and must be followed by NEW.

In this article we will refer to MEM1 (normal RAM) and MEM2 (PRK file memory).
In the position of N in CALL P(N) a number (constant) must be used (an integer between -4 and 13821) which points to the spot in the RAM stack where OLD will start loading instead of what otherwise would have been the starting address reserved for OLD.
The memory space below this point is the thus created MEM2 and consists of N bytes to be used for PRK data.

Usual memory:    
|            |   
|   usual    |   
|   RAM      |   
|            |   
|  16000     |   
|  bytes     |   
|            |   
|                | 
|  MEM1 (basic)  | 
|  16000-N       | 
|   bytes        | 
| MEM2 (prk data)|
|  N bytes       | 
If you need a large MEM2 (e.g. because a large PRK file has to be loaded) then N must he in the higher range. This obviously at the same time restricts the size of MEM1 for your Basic program.

If on the other hand you have a large TI Basic program or need to load a lot of "normal" data, but still you want to interact with a PRK file as well, then you are best off with a large MEM1 and a small MEM2 when in the CALL P(N) statement you assign a low value to N.

If you are still with us then it will dawn upon you that this beautiful mechanism enables you to freely choose the ratio of MEM1 against MEM2 to suit any particular application. MEM1 is cleared and loaded with programs and data in the usual way with NEW, OLD, SAVE, INPUT and PRINT without affecting MEM2 in any way. PRK data are loaded in MEM2 with the statement:
resulting in the usual cassette prompts which will now read data previously generated by the PRK module in its normal mode.
An error message: ERROR DETECTED IN DATA may mean that MEM2 is not large enough to contain the PRK data and a new CALL P(N) with a higher N must be entered (and followed by NEW). The quickest and surest way to remove the previous CALL P is to switch the console off and on again.

MEM1 can be used:
a. Normally as if MEM2 had not been prepared
b. In the direct node interacting with the loaded PRK data
c. To load a program in TI Basic that interacts with PRK data or even loads or saves PRK data when this program is RUN, as program lines with CALL L and CALL S (you guessed it, S for save) are permitted.

The syntax and parameters of CALL L and CALL S are:
CALL L("CS1",C) and CALL S("CS1",C)
C is a control variable that gets a value 0 if loading or saving has been successful. When an error has been detected the value of C in not equal to 0.
Instead of "CS1" also "DSK1" or "RS232" may be used for similar interaction with these devices.

There are only 2 statements that can be used in the TI Basic (or rather Enhanced Basic, a term coined by Peter Brooks of TIHOME, the British user group) dominating MEM1 TI Basic area) that cross the borderline between MEM1 and MEM2.
These two statements are:
The CALL G ( G for getput) statement has a write mode and a read mode.
In the write mode it enables the user to change PRK data, which might also have been changed using the normal procedures of the PRK module (change a page and mathematical transformations).
But the values can also be taken from variables which in turn get their values from the whole bag of tricks of TI Basic including string handling (which otherwise lacks in the module). Needless to say, this dramatically enhances the versatile use of the PRK data, since the saved data (CALL S) can be reloaded in the module mode, permitting their further use "module fashion".

The syntax and parameters of CALL G are:
Write mode: CALL G (0,PAGE,ITEM,VALUE)
MIS in read mode is a control variable: if data found then MIS=0. When no data found MIS=1.
Note 1: If a string variable is used for VALUE (e.g. VALUE$) and the ITEM type was chosen as "characters", then strings can be handled.
Note 2: CALL G(2,PAGE,ITEM,VALUE) writes "nothing" (=missing data) in the assigned place. The value or VALUE has no meaning.
Note 3: Although not mentioned each time, these techniques also work with the Statistics module.

CALL H affects the header, i.e. those choices that the PRK does not permit you to alter, once you have okayed the file structure.

Changing the names of FILES and ITEMS is a cinch.
Changing the type or width if ITEMS is also easy, but the results are usually not the ones aimed for, because all data are written sequentially (as beads glued on their string). Nevertheless it is possible to change any entry for the file structure maintaining the right data in their correct place, but this requires routing through a special TI Basic program.
This will be discussed in a future article. For those of you too impatient for this feature we recommend you buy the command module "Personal Report Generator". You then overcome the frustration of having spent days and days entering data in a PRK program and then coming to the conclusion that a small change in file structure is necessary forcing you to start from scratch.

The syntax and parameters of CALL H are:
   Read mode: CALL H(1,INFO,ITEM,VALUE)
   Write mode: CALL H(0,INFO,ITEM,VALUE)
   INFO Stands for
    1 File name (maximum of 9 characters)
    2 Day of the month
    3 Month
    4 Year
    5 * Number of items per page
    6 * Number of pages
    7 * Length of header in bytes
    8 * Length of each page in bytes
    9 Item name (maximum of 9 characters)
    10 Type of item (1 = char; 2 = integers; 3 = decimals; 4 = scientific)
    11 Width of item
    12 Number of decimal places
    13 * Amount of memory required for this item in bytes
    14 * Position of item in page

* = this value is automatically calculated and placed by PRK mode
The ITEM value is of no importance for those INFO values between 0 and 9
Setting up the header (i.e. file structure) is easiest in the module mode (Let's begin- create a file), but if you insist on doing this from TI Basic start with INFO 9 to 12 before going on to INFO 1-4.

We intend to give examples of the practical use of all this knowledge in future articles covering such subjects as an easier way to save arrays and word processing in PRK files.

Although Texas Instruments are obviously aware of these possibilities they have not considered them perfect enough to document them and "sell" them officially. The authors declare that although inside information from TI made this article possible, that in no way can Texas Instruments be held responsible for its contents, nor are the authors who present these data in good faith but without any warranty whatsoever.
Still we consider knowledge of Enhanced Basic important for a complete enjoyment of your TI-99/4(A). And that is what counts!

=================== =============
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Enhanced Basic for efficient loading/saving of arrays
by Franc Grootjen and Paul Karis Blxxxgras 2. 39NN AA Veenendaal, The Netherlands

This article will only make sense to those who have familiarised themselves with Enhanced Basic - the term Peter Brooks of TIHOME, the British user group, invented for the extras provided by CALL A, CALL D, CALL P, CALL L, CALL S, CALL G, and CALL H in combination with a Personal Record Keeping or Statistics Module.

Imagine having completed 150 observations with values between 0-100 and that you want to save these values on tape. You don't want to use the PRK or STAT mode as the standard possibilities of these modules are too restricted for your intentions. TI Basic allows us to OPEN and PRINT #N and so writing data on tape, but this method has several drawbacks:
Saving and loading consume a lot of time and tape. Frequently the pilot tone alone, marking the start of each record, takes longer than the actual time required for data transmission. Waiting time is wasted time.
The compacting of data that sometimes partly solves the first problem in itself is complicated. (e.g. the string "2/2.3/5/6.7/3.4/1.3/3/34/123/4.5" can be written as one variable but used to transmit 10 numerical values).
There is no built-in data check possibility like we have for program saving.
When an error occurs the program BREAKs and cannot be CONtinued, and the data loaded cannot be used and must he loaded again. The same holds true if a small alteration needs to be made in the program after the data are loaded.

Enhanced Basic does away with all these problems.

Back to our example: Let us presume that the 150 observations are held in the array ARRAY(ITEM), At this point we would like to remind you that the use of Enhanced Basic requires you to prepare your computer with CALL P before typing in or loading the following subroutines or programs containing these subroutines.

10010 CALL H(0,5,1,1) 
10020 CALL H(0,10,1,2) 
10030 CALL H(0,11,1,2) 
10040 FOR ITEM=1 TO 150 
10050 CALL G(0,1,1,ARRAY(ITE
10060 NEXT ITEM  
10070 CALL S("CS1",Y) 
10080 REM END Of SUBR 
10090 RETURN
10110 CALL L("CS1",Y) 
10120 FOR ITEM=1 TO 150 
10130 CALL G(1,1,1,MIS,ARRAY
10140 NEXT ITEM 
10160 RETURN
When your main program is at a point that you want to save the values of the array ARRAY() it only takes a line
GOSUB 10000 to do so.
In the same way GOSUB 10100 will fill the array with the values played from the tape.

Detailed explanation:
10010 Tells the computer that one item will be used per page.
10020 Determines this item to be of type 2 (= integer)
10030 Reveals that you do not intend to have values beyond 99. Width is 2.
10040-10060 Stores all 150 values of the elements of array ARRAY() in MEM2.
In PRK language item 1 on page ITEM gets a value of ARRAY(ITEM)
. 10070 Saves the array as a PRK file from MEM2. CHECK TAPE (Y/N) is asked.
10100 Loads PRK file from tape in MEM2
10120-10140 A loop that fills array ARRAY() with the values in MEM2.
We recommend you study this example and you will discover other possibilities that are meaningful to you. Change lines 10020 and 10030 to suit your data. Use nested loops for multi-dimensional arrays. Use your head as in computing: The sky is the limit.

Rambles by Stephen Shaw

Not many days after a phone call from Canada arranging for me to distribute some Canadian programs in the UK, I have received a phone call from even more distant shores - Perth - in Australia. Even at the speed of light there is an appreciable echo, a bit disconcerting. (That is via satellite by the way!). The following news was passed on:
Extended Basic v110 - variations:
a. !@P+ and !@P- does not have a separate single byte internal code It is stored just like that, in four bytes.
b. Everything I've written regarding memory locations for your program is for v100. If you use v110 the first 24 bytes are occupied with something else. Therefore if you use CALL LOAD to amend a program, when using 110 you must subtract 24 from the memory location - e.g. an Extended Basic program line stored starting at location -200 in v100 will start at -224 in v110. This need not prevent portability of programs - use CALL VERSION as follows:
Then when using call load, use the form:
where LOC is the location when using v100.
Think about it - if using v110, then VN will be 24 if using v100, then VN will be nil.
The minus sign has been used (-VN) because program locations are in the negative side of memory, and to increase a negative number, you take more away.

c. Another unpublished difference - my benchmark timings for XB in June issue were for v100. You should find v110 behaving as "speeded-up" v100.
This is because v110 automatically sets memory location -31878 to the number of sprites you are using, without the need for Expansion Memory! So you lucky v110 owners have a faster version: your programs will on average run 30% faster in XB than in TI Basic. If you have v110 - don't bother putting in the "speed-up" line - you don't need it. If you have v100 you need the Expansion RAM and need to use:
CALL INIT :: CALL LOAD(-31878,0)

Acknowledgment - the April article on disks came from Australia. That's all from the Antipodes.

Taking a week off work recently I was impressed by the number of times the phone rang. If you need to ring me, please do so after 7:00PM and not on Wednesdays. I prefer letters, they give me time to think!

99'er Magazine Issue 5 - for those of you not yet subscribers - Contained some VERY good action games in Extended Basic, and a rather easy version of Reversi (Othello).

Contained a detailed review of the mis-named Mini Memory module - not just 4K of RAM but a whole lot more. With this module you may write and run programs in Assembly code with only the console and a tape recorder - no need for a disk system or Expansion RAM.
You can address every byte in the machine, including switching to a 40-character screen width, and can define 768 different characters at once (that does however take up to 12K of memory). This magic module SOUNDS very exciting - I have one on order from the States, and will report in due course.
Note: Owners of the old 99/4: You have a different VDP chip and can't define 768 characters - sorry. The demo program supplied will not therefore work on a 99/4 - it's a hi-res graphics demo using 768 characters.

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67MB pdf file from of 99er Magazine Volume 1 issue 5, which was not dated.

99/4A and Computer and Video Games
You will have seen me mention in these columns the magazine Computer & Video Games.
Now, TIHOME has several members, but the Good Editor of the above magazine tells me that NONE of you has sent him a program to publish for the 99/4A. That's why you haven't seen any listings. It is an excellent magazine, and several of the programs listed are fairly easy to translate for the 99/4A.

I am informed that the 99/4A will be included in the issues dated Oct, Nov and Dec 1982. These are available in the middle of Sept, Oct and Nov 82!

The magazine pays GBP 10 for first publication and sends you a free issue too. You may specifically reserve all other rights. If you want to see programs for the 99/4A published you know what to do now. SEND THEM to C&VG mag. At the very least write to the Good Editor and thank him for his interest. Unless he receives a good response to the Oct-Dec issues he will probably not give the 99/4A another glance. It's up to YOU (stop snoring at the back!).

* * *
Four branches of Micro-C are experimentally stocking some of my cassette software for the 99/4A in TI Basic. (Manchester, Birmingham, Leicester, Southampton)
* * *
TI-99/4 vs. 99/4A differences
There are several variations on the TI system which you must know about if you wish your programs to run on every combination.
Firstly, the different consoles:
The most important difference is in using the split keyboard. In particular, you must not use keys returning values of 13, 16, or 17. The two consoles use different keys for these codes.
If you use keys X and M, supposedly returning value 0, when testing for this value you should not directly equate with zero, as the 99/4A will return False. You should use, for instance:
IF B+1=1 THEN ...
The A model has a different VDP chip. If you are developing an Assembly Language routine or program which addresses this chip you should test-run on a 99/4 if available, or indicate that your program/routine may not work with a 99/4. As an example - with the A you may define 768 characters. This is not possible on the 99/4.
The old 99/4 only has available CALL KEY 0, 1, and 2. The other CALLS will not cause a crash, but they will have NO effect.
The old 99/4 does not have a lower case character set - the characters are blanks. If you use a 99/4 do not assume any blank characters - if you use an A, do not assume lower case will be printed.

For use on either console, you may wish to add the following, if your A program uses lower case (and if it is not vital to the programs)

110 CALL KEY(2,A,B) 
120 CALL KEY(0,C,D) 
130 IF (D=0)*(B=0) THEN 110 
140 CALL KEY(2,A,B) 
150 IF A <> 13 THEN 1000 
160 FOR A=65 TO 90 
170 CALL CHAR(A+32,CHR$(A)) 
180 NEXT A 
CALL KEY(2 …) is repeated in case ENTER is pressed when the computer is between 110 and 120!
In Extended Basic you may use: 
172 B$="0000"&SEG$(A$,1,4)&SE
174 CALL CHAR(A+32,B$)
This will give the 99/4 the small letters. Only one major problem - the area the program is stored in in memory is very slightly different - 24 bytes adrift.
If you use CALL LOAD to amend a program line, you must use:
100 CALL VERSION(VN) :: VN=(VN-100)*2.4
then ADD VN to your program location if it is a 99/4 location:
CALL LOAD(LOCATION-VN,VALUE) (To increase a minus you must subtract)
If you have obtained the location using the A, then deduct VN:
CALL LOAD (LOCATION+VN,VALUE) (A minus is reduced by addition)
Follow this guidance and there should be no problems.

CALL LOAD, or how an Extended Basic program can alter its own lines

Note: If you have v110 Extended Basic,
for listing A, in line 150, use
FOR B=-32 TO -48 STEP -1

or listing B, line 150, use
CALL LOAD(-47,156,199,etc ... )

Version A, suggested from an article in 99'er Magazine

100 GOTO 140 
110 PRINT "!!!!!!!!!!!!!" 
120 END 
130 STOP 
150 FOR B=-8 TO -24 STEP -1 
160 READ Z 
180 NEXT B 
190 DATA 69,84,69,76,80,77,7
200 GOTO 110 
1000 FOR Z=0 TO -28 STEP -1 
;A;CHR$(A),:: NEXT Z 
1001 END 

Version B, suggest by comparison to CALL PEEK
100 GOTO 140 
110 PRINT "!!!!!!!!!!!!!" 
120 END 
130 STOP 
150 CALL LOAD(-23,156,199,13
170 GOTO 110 
180 END 
This version an original SJS creation.
Note: Switch on Expansion Memory then Console.
Select Extended Basic then key in your selected program EXACTLY as shown above.
If you need to edit or amend a line, enter NEW and start again to maintain the order in memory.
RUN the program then LIST it - notice any difference?

Program B is neater as it allows you to LOAD a line in normal order.
Note: The last data item in Program A is the number of characters in the line (including command characters and including the number 17 itself. It is not necessary but is included to remind you that writing lines this way you may not alter the length of the line! If it starts 17 long it should remain 17 long!

With this type of procedure you can no place a "HISCORE" for your games into your programs - and save with the program instead of using a separate data file.
Don't forget to also put in your program a "reset" feature.

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Advanced Programming: Graphics Mode 3 (Multicolor Graphics)
The programs which follow will only run if you have:
a) Extended Basic, b) Expansion Memory.
The CALL KEY is important - when you press a key, the value you have loaded into CPU RAM address -31788 is transferred to VDP Register 1. This simulates Graphics Mode 3 - (to make full use you must use Assembly Language, not Extended Basic)

In Mode 3, you have each character position divided into 4 small squares. Every small square can be any one of the 16 colors available.

As the final list illustrates, the Mode 3 Color Table is in the same area of memory as Mode 1 Character Definition Table which permits us to use those small squares in Extended Basic.

If you place a vertical column of 4 characters on the screen, giving a 2 by 8 grid of small squares, you can manipulate the small squares by redefining the character forming the column

| 16 |  15 |
| 14 |  13 |
| 12 |  11 |
| 10 |  9  |
| 8  |  7  |
| 6  |  5  |
| 4  |  3  |
| 2  |  1  |
1 = rightmost defining position, and 16 = leftmost.

The VALUE defines the color (1 to F), the position in the definition string defines which of the 16 small squares is to be that color.

Note what happens when you scroll. Note: It is wise NOT to use CALL SOUND.

Keep pressing keys to return to normal afterwards. If the screen appears to lock out in a funny pattern, enter a letter and press ENTER - that should clear it. If all else fails, switch off.

Have fun with these:

110 B$="1234567890ABCDEF1234 
120 FOR CH=32 TO 136 
130 FOR C=1 TO 16 
140 CH$=CH$&SEG$(B$,32*RND+1 
150 NEXT C 
160 CALL CHAR(CH,CH$):: CH$= 
170 NEXT CH 
180 CALL SOUND(500,440,0) !b 
efore LOAD 
200 CALL LOAD(-31788,204) 
220 CALL KEY(0,A,B)
230 IF B<1 THEN 220 
240 CALL HCHAR(1,1,32+FLAG,7 
250 FOR CH=32 TO 95 
270 CALL CHAR(32+FLAG,B$) 
280 FOR DL=1 TO 200:: NEXT D 
290 NEXT CH 
300 FLAG=FLAG+1 
310 IF FLAG<100 THEN 240 
110 CALL LOAD(-31788,204) 
120 CALL KEY(0,A,B) 
130 IF B<1 THEN 120 
140 CALL HCHAR(1,1,45,200) 
150 FOR Z=1 TO 57 
160 FOR X=1 TO 14 
170 PRINT CHR$(Z+30); 
180 NEXT X 
190 FOR DL=1 TO 500:: NEXT D 
200 NEXT Z 
210 CALL LOAD(-31788,224) !n 
ormal value 
220 CALL KEY(0,A,B) 
230 IF B<1 THEN 220 
240 END 
120 CALL LOAD(-31788,204) 
130 CALL KEY(0,A,B):: IF B<1 
THEN 130 
140 B$="1234567890000ABCDEEE 
150 FOR T=32 TO 100 
170 NEXT T 
180 FOR Z=1 TO 30 
190 CALL HCHAR(23*RND+1,31*R 
200 NEXT Z 
210 IF FLAG=2 THEN 150 
220 FOR Z=1 TO 700 
230 CALL HCHAR(22*RND+2,30*R 
240 NEXT Z
250 FLAG=2:: GOTO 150 
260 END 


100 A$="00000000000000110000 
110 FOR A=32 TO 60 STEP 3:: 
130 CALL LOAD(-31788,204) 
140 CALL KEY(0,A,B) 
150 IF B<1 THEN 140 
155 CALL HCHAR(1,1,32,770) 
160 FOR I=1 TO 16 
170 CALL CHAR(32,SEG$(A$,I,1 
180 FOR DL=1 TO 3E3:: NEXT D 
190 NEXT I 
200 END 

CALL SOUND - accuracy and range of frequency

Having read your manual and seen just how high a frequency you may specify with CALL SOUND, did you wonder why TI claims a music range of only four octaves? Because when you go over that, the accuracy of the frequency suffers.

Using the notes D and D sharp, and starting from the D above the A above high C:

Intended   Theoretical Output 
Frequency   Frequency 
   1175      1177 
   1245      1243 
Pretty close. Now, the same notes, going up an octave at a time:
   2350      2330 
   2490      2486 
   4700      4661 
   4980      5085 
   9400      9322 
   9960     10169 
  18800     18643 
  19920     18643  
! no error in my typing here
Notice those last two - a bit out.
This is because the frequencies played are all denominators of a constant, and as the frequency rises, the number of playable frequencies drops.
This will affect the CALL SOUND routine I gave for playing sounds below 110Hz.(TIHOME, April 82).
For bass sounds the error is quite low, but as the frequency of the third sound generator rises, so does the error! in practice you should not try to play a note over 300Hz using this formula.

If you don't have TIHOME April 82, here is a little list for you to enter and try:

110 CALL SOUND(400,FREQ,5) 
120 CALL SOUND(400,30000,30,
130 CALL KEY(0,A,B) 
140 IF B=0 THEN 110 
150 GOTO 100 
Note: The computer plays a note for a duration of N sixtieths of a second - not in milliseconds.
The minimum duration is thus 17ms - in theory. In practice, it takes time to evaluate the instructions! (about 40ms.)
It appears that the multiplier used gives an output approximate to the frequency. The frequency of the third generator sets the "shift rate" of a 15 stage divider network. With feedback. That's what the Editor/Assembler manual says anyway.

Faster Banthorpe
In the last issue the Banthorpe Plot ran slightly slowly. By omitting every other horizontal line and calculating the right hand side by mirroring the left hand side, the time can be reduced.

A little explanation to help you along:
The subroutine begins at 120 and ends at 320. The REMs which appear in earlier versions have been removed to save space. The initialization is split into two parts; line 100, which dimensions the array (see Guidelines For Software Contributors, last issue), and lines 330 to 390 which set up the screen format and color and create the constants. Note that HR$ is specific to this program only. I came across information similar to that given by Stephen Shaw about X*X being faster than X^2 and have changed lines accordingly.

The variables R and C are used to pass the plot co-ordinates to the subroutine.

The subroutine variable list is: B, C, H, I, P, R, S, X, Y, B$, H$, I$, Z$, C$(), and of those, S, B$, H$, Z$, and C$() should not be modified by the main routine(s), although C$() may be under certain circumstances.

Observant plotting addicts may notice that HR$ is similar to the mirror-image reversal string used in Designs For Fun.

Here is the revised listing based on suggestions from Bill van Kerkoerle:

100 DIM C$(128)
110 GOTO 330
120 Y=INT(R/8+0.875)
130 X=INT(C/8+0.875)
150 IF H>31 THEN 220
160 IF S=95 THEN 320
170 S=S+1
180 C$(S-31)=Z$&CHR$(Y)&CHR$
210 H=S
220 H=H-31
230 B=C-X*8+8
240 P=2*R-16*Y+16+(B<5)
250 IF B<5 THEN 270
260 B=B-4
270 I$=SEG$(B$,POS(H$,SEG$(C
280 I$=SEG$(I$,1,B-1)&"1"&SE
290 I=POS(B$,I$,1)
300 C$(H)=SEG$(C$(H),1,P-1)&
310 CALL CHAR(H+31,SEG$(C$(H
340 S=31
350 CALL HCHAR(1,1,S,768)
360 B$="0000.0001.0010.0011.
370 H$="0....1....2....3....
380 HR$="0....8....4....C...
390 Z$="0000000000000000"
400 H1=192
410 V=104
420 X1=H1/2
430 X2=X1*X1
440 Y1=V/2
450 Y2=V/4
460 FOR X5=0 TO X1 STEP 2
470 X4=X5*X5
480 M=-Y1
490 A=SQR(X2-X4)
500 FOR I1=-A TO A STEP V/10
510 R1=SQR(X4+I1*I1)/X1
520 F=(R1-1)*SIN(R1*12)
530 R=INT(I1/5+F*Y2)
540 IF R<=M THEN 590
550 M=R
560 R=Y1-R
570 C=X1-X5+32
580 GOSUB 120
590 NEXT I1
600 NEXT X5
610 H=S-31
620 FOR K=1 TO H
630 P$=C$(K)
640 Y=ASC(SEG$(P$,17,1))
650 X=33-ASC(SEG$(P$,18,1))
660 FOR L=2 TO 16 STEP 2
670 I$=SEG$(P$,L,1)
680 J$=SEG$(P$,L-1,1)
690 I$=SEG$(HR$,POS(H$,I$,1)
700 J$=SEG$(HR$,POS(H$,J$,1)
710 C$(K+H)=C$(K+H)&I$&J$
720 NEXT L
730 CALL CHAR(K+S,C$(K+H))
750 NEXT K
760 GOTO 760

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From Paul Dicks:

Stop Press
To encourage TIHOME members to submit articles and programs to the commercial micro press, Texas Instruments will give you a module of your choice up to a price of GBP 50 for each article or program published from now till December 31, 1982. Send proof of publication in the form of a photocopy of the magazine page containing your entry to R. Frowd, Texas Instruments, Manton Lane, Bedford, Beds.
After the finishing date Robin Frowd and Paul Dicks will decide which is the best of the articles and the winner will receive a language module of their choice, i.e. Editor/Assembler, Logo, Mini Memory, Extended Basic, Speech Synthesiser.
This offer does not apply to employees of TI or TIHOME. Nor does Tidings count as a commercial publication.

* * *
Membership continues to rise and now stands at abut 400. I won't say that the higher the membership the more notice TI takes of us, but I'm sure it has some effect. As the membership rises I am having to introduce strict office routines or else I will lose track of what I have done and what still needs to be done.
All members have a membership number already and pretty soon I shall let you into the secret. If you quoted it on your letters it would certainly help when I get letters with almost no address, signed "Yours Harry". While I appreciate Harry's letter, it would be useful to know who he is!

============== ============ ===========

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