TI99/4 and 4a differences
Before the TI-99/4a there was the TI-99/4, without the a.
The 4a introduced some changes which made some module manuals hard to follow, and some programs difficult to use. This article is intended to help you if you have these problems.
The most obvious difference between the models of console was the keyboard, which had a major redesign, which caused the problems listed above. There was a little less memory for programs (256 bytes less).
See also Console design
The keyboard change meant that for programs to run on BOTH consoles, when using the split keyboard (CALL KEY 1 and 2) you cannot use keys which return the codes 13, 16, and 17. When using a split keyboard on the "A" the key value 0 (zero) does NOT equate to zero - you must use indirect means such as IF A+1 = 1.
The 99/4A has a different character set - not only are small characters made available (with internal routines) but the big letters are BIGGER by one pixel. The result: A fairly crowded screen AND - if you are fortunate and have a thermal printer - printer TP. U. S. E. (screen dump) works badly, with no space between letters, vertically).
Here are the big keyboard changes which will affect earlier modules and programs. This may even help with the use of emulators...
TI-99/4 TI-99/4A Name keys keys AID SHIFT A FCTN 7 CLEAR SHIFT C FCTN 4 DELete SHIFT F FCTN 1 INSert SHIFT G FCTN 2 QUIT SHIFT Q FCTN = REDO SHIFT R FCTN 8 ERASE SHIFT T FCTN 3 LEFT arrow SHIFT S FCTN S RIGHT arrow SHIFT D FCTN D DOWN arrow SHIFT X FCTN X UP arrow SHIFT E FCTN E PROC'D SHIFT V FCTN 6 BEGIN SHIFT W FCTN 5 BACK SHIFT Z FCTN 9 ENTER ENTER ENTER
Some programs used special keys which were affected.
The left column is the 99/4 keys and the right column is for the 99/4a (as above table):
Early Learning Fun
Instructions SHIFT P FCTN P
AID A or SHIFT A SHIFT A or FCTN 7 REDO R or SHIFT R SHIFT R or FCTN 8 BEGIN W or SHIFT W SHIFT W or FCTN 5
Addition and Subtraction 1, Addition and Subtraction 2, and Multiplication 1 modules.
On the 99/4 some function keys operate both shifted and unshifted.
However on the TI-99/4A Computer, these functions are accessed by pressing either SHIFT and the letter key or FCTN and the function key. For example, to use the AID function, you can press SHIFT A or FCTN 7.
Print SHIFT P FCTN P Home SHIFT H SHIFT < (less than)
Answers SHIFT L = (equal sign)
BACKUP SHIFT B FCTN I HELP SHIFT H SHIFT < (less than) CLEAR SHIFT C FCTN 4 RESIGN SHIFT E FCTN E DRAW SHIFT D FCTN D TIME OUT SHIFT T FCTN 3 REPLAY SHIFT R FCTN 8 STORE SHIFT X FCTN X SWITCH SHIFT S FCTN S POSITION SHIFT P FCTN P MODE CHANGE SHIFT M ; (semicolon) QUIT SHIFT Q FCTN = (equal sign)
On some 99/4a consoles if you opened two files whose filenames differed in length by one character the system would lock up.
If alpha lock is DOWN on the 99/4a, the joystick will not function correctly,
Extended Basic Sprites
On some TI99/4a consoles, a sprite on row 208 (which is off screen) may cause all sprites with a higher sprite number to disappear and if the sprite is moving, the other higher numbered sprites will all flicker off and on together.