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This page contains TI99/4A Programming hints, tips for TI99/4A Module care, and using TI Writer.

For - was it fifteen years? - MICROpendium was a commercial magazine supporting the TI99/4A computer.

One of the longest running professional supporters, writing in many magazines, was Cheryl Whitelaw, writing as Regena.

For this article some selected text from the January 1988 issue of Micropendium, retaining the original column widths and hyphenations, starting with an article by- Regena-

Are you still having FUN with your computer? Life has been so hectic for me the last little while that I haven't had as much time to program. Once in a while, however, I do like to sit at the computer and program. (In fact, I'd rather program than write the articles, but of course most programmers are like that.)
This month I am going to offer you a few "reminder" programming hints. These may be things you've known about for a long time but haven't used for a while or they may be things you use in every program you write. I hope you find these hints helpful.

When you start a program, number your lines by 10s (100, 110, 120, etc.). If you need to add lines later, you'll be able to insert them with numbers within existing lines. You may want to start major sections with 1000, 2000, 3000, and so forth, so you can keep track of them. When the program is working in final form, you can use RESequence to renumber your lines. If you really need to conserve memory, you can RES 1,1 to number your lines by ones, starting with Line l.

I usually clear the screen with CALL CLEAR, but you can use other methods. For example, if you have all black printing on the screen, you can turn the screen black with CALL SCREEN(2). If you have graphics on the screen, you can change the color of those characters to "invisible" with CALL COLOR(S,1,1), where S is the set number for the characters involved. Or you may change the characters to be a blank. For example, if you have Character 99 defined as a tree, and there are trees randomly placed on the screen, you can make all the trees disappear with
CALL CHAR(99,"")

You may fill the screens with blanks with statements such as
CALL HCHAR(1,1,32,768)
CALL VCHAR(1,1,32,768)

The computer starts in the upper left corner, Row 1 and Column 1, and places the blank character or space in each position for 24 rows and 32 columns.

You may also use CALL HCHAR or CALL VCHAR to clear parts of the screen. As in the above examples, you do not need to restrict the number of characters in the fourth parameter to one row or. one column. Let's say you have graphics on the top half of the screen and some printing on the bottom half. If you want to erase the bottom part of the screen only, you can use
CALL HCHAR(13,1,32,32*12)

Another hint is to remember that the colon in the PRINT statement means to go to the next line. If you are translating from other computer versions of BASIC, you may have noticed that the colon is a statement separator. If you want to print several blank lines, you need to use PRINT or? for each line you want in other versions of BASIC. In TI BASIC, you may use the colon, such as
You may use colons along with other numbers or strings, such as

Remember to use the ON-GOTO procedure rather than a series of IF-THEN statements. An example of this situation is when you ask the user to choose among several choices. Let's say you have a menu screen of choices A, B, C and D. You may use IF-THEN statements to branch, such as if the answer is A, go to Line 1000; if the answer is B, go to Line 2000; if the answer is C, go to Line 3000; if the answer is D, go to Line 4000.

A more efficient way to direct the computer is to use the ON-GOIO. If you have used CALL KEY to get the answer, you will get the ASCII code of the ASCII key pressed. First make sure the key pressed is A, B, C or D, then branch:
410 IF (K(65)+(K >68) THEN 400
420 ON K-64 GOTO 1000,2000,3000.4000

To create a pause or delay in a program, you may use either a FOR-NEXT loop or a CALL SOUND delay:
310 FOR DELAY =1 TO 400
350 CALL SOUND (500,9999,30)
360 CALL SOUND (1,9999,30)

Sometimes when you read and process data in a FOR-NEXT loop you will notice a slight delay before the last data item. You can avoid the delay if you use one more loop than you need and add a dummy variable. For example, if you are printing lots of graphic characters on the screen you might notice a delay before the last character is put on. Increase the loop and use the last data item twice (print the last character in the same place two times).

300 FOR N=1 to 25
330 NEXT N
340 DATA 3,5,42,... (your data items here)
350 DATA... 10,12,65,10,12,65

If you really have to "squeeze" your program to fit in the available memory, remove all the REMark statements. Use short variable names. For example, instead of NUMERATOR and DENOMINATOR as variable names in a fractions program, use N and D. Also look through your program for any repetitious programming that could be more efficient using subroutines or FOR-NEXT loops or DATA statements.

If you have a lot of graphic characters, redefine the lowercase letters and symbols in ASCII codes 91 through 126. Use PRINT rather than CALL HCHAR or CALL VCHAR to place the characters on the screens faster. For example, redefine the characters, then use a statement such as PRINT "abcd" rather than four CALL HCHAR statements. Many of the other character numbers are the same as CONTROL characters and may also be printed, although your listing will contain funny looking characters and will be harder to understand. You may also use a method such as
PRINT CHR$(130);CHR$(131)
;" ";CHR$(132)
In speech programming with the Terminal Emulator II command module, I like to use the caret symbol before the word or phrase and the period after it to get a more natural voice. For example,

When you use IF-THEN statements, don't forget that we also have the ELSE option. You may specify a line number for branching if the condition is true and another line number if the condition is not true:
Also, you may check more than one condition in an IF-THEN statement by using parentheses and the + and * signs.
IF (A=B)*(C>D) THEN 300

You may combine strings to save data that otherwise might be in several parts and use lots of memory. For example, if you have a series of numbers 5,7,1,3,8,9, you may read them in as 571389 then use the SEG$ function to separate them for calculations or other use: 200 READ N$,A$
210 FOR M=1 TO 6
220 X$=SEG$(A$,M,1)
230 NEXT M
400 DATA RICK,571389

My final reminder is that if you have the disk system and do not need a lot of open files, gain valuable bytes by using this procedure:
1. From the title screen, press any key to begin.
2. Press 1 for TI BASIC.
3. Enter CALL FILES(1)
4. Enter NEW
5. Proceed as usual.

I use this as a standard procedure every time I sit down to program. Some of my longer programs will not run (you'll get an OUTOF MEMORY error) if you do not do this before loading and running the program.



Having trouble with computer lockups or just getting your computer started (such as screen garbage when you go into Extended BASIC)? If so the following ... may help you solve your problem.
...taken from the Central Iowa Users Group newsletter. The article is by Ron Rutledge.
Readers who use the suggestions for cleaning the 4A and its cartridges do so at their own risk. Ed.

Dirty contacts can screw-up any electrical device and the 4A is not an exception. The only place you are likely to run into thisp roblem is in using command modules. Both the module contacts and the port itself can become dirty, but cleaning the port itself is a big job as you have to disassemble the console. The good news is that cleaning the cartridge will almost always suffice and canbe done quickly without special tools or cleaners. All you need is a screwdriver, a rag, a standard pencil eraser, and in some casesa medium Phillips screwdriver.

Remove the screw from the center of the cartridge if there is one. Then pry the clips in the outside slots to the bottom left and right of the center screw. If there is a clip in the center instead of a screw, pry it back after the bottom left and right slots are pried off. If it should bend off don't worry, it won't effect the performance of your module.

The module board can now be removed. Do this carefully and note how the spring-loaded "door" is assembled, if there is one, so that you can put it back together if it pops out.

Once the board has been removed take the rag (a facial tissue will work but cloth is better) and rub off any residue from the edge connector contacts. Do the contacts on both sides if the module has them. Once the worst is removed take any soft rubber eraser and "erase" the contacts until they become dry, clean and shiny.

You need to do only the outer half of the contacts as that is much as ever gets worn (you can see the scratch marks on the contacts).

After the cleaning, put the cartridge back together and go.Symptoms of dirty contacts include the console locking-up and unusual errors where none occurred before. (For example, my dirty Extended BASIC cartridge gives me syntax errors in programs where there were no errors when it was clean.)

Don't jump to clean a cartridge on the first appearance of an error. Such problems may be caused by static and not having the module firmly seated in the cartridge port, among other things. But if you have a continuing problem, cleaning the contacts is quick and cheap and may get you running again.



Get to the bottom of TI-Writer

Know how to get to the end of a document while using the TI-Writer editor? Just enter S (for Show Line) from the command line and then enter E. The next thing you know the cursor will be on the last line of the document. To get back to the top, enter S and then l.

The letter E for "end" can also be used when deleting, copying or moving lines.

For example, after entering D for delete in the command line, enter 10 E to delete everything from line number 10 to the end of the document.


Time-saver for XBASIC users The following tip appeared in Ozark 99'er News, the newsletter of the Ozark 99'er User Group. Harold Hoyt gets the credit for it.

Lots of programmers put their program identification in line 100 as a REMark. Six months later, listing the program, it answers your questions. What the heck is this? When did I write it'? Why did I write it?

I've been pulling a little trick in XBASICthat the more I do it, the handier it seems. I add another program line, so that the beginning of my program looks like this:
100 ! Prog 'PROGRAMNAM' H. Hoyt
7/28/87 Demonstration Prog

Note all of the 10 characters in the program name can be used to describe the program. One of my friends was using single letter program names because he hated the extra typing.

If you type line 100 program description data once, and then hit Enter followed by FCTN 8 (REDO), you can edit out 00 in 100 to create line I and further edit it to create SAVE DSK1.PROGRAMNAM and delete the rest of the stuff. By itself, this wouldn't be worth the trouble, but just see what happens next.

After line 1 has been properly entered, hit FCTN 8 again and then FCTN 3 (DELETE) to eat the line number. space and exclamation mark. What results is SAVE DSK1.PROGRAMNAM in the screen buffer. Just hit Enter and the program is automatically saved. This saves so much typing that it encourages you to save program pieces more frequently, reducing the loss in case of a program crash.


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