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).

Call Key

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.

Character Set

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).

Keyboard Changes

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

Early Reading

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

Mathematics Modules

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.

Music Maker

Print  SHIFT P    FCTN P
Home   SHIFT H    SHIFT < (less than)

Number Magic

Answers  SHIFT L     = (equal sign)

Video Chess

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)

Opening Files

On some 99/4a consoles if you opened two files whose filenames differed in length by one character the system would lock up.

Joysticks

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.