Texas Instruments TI-99/4A User Reference Guide

KEY sUbprogram
The return-variable must be a numeric variable. The computer will
place in return-variable the numeric character code represented by
the key pressed. If the unit used is the console keyboard (unit 0),
the character codes are the normal ASCII codes and may range
from 0-127. If you are using the split keyboard (unit 1 and/or
unit 2), the character codes will be 0 through 19.
The status'variable is a numeric variable which serves as an
indicator to let you know what happened at the keyboard. The
computer will return one of the following codes to the status'
variable
after performing the CALL KEY routine:
• +1 a new key was pressed since the last performance
of the CALL KEY routine
• -1 tht> ~ame key was. pressed during the performance
of CALL KEY as was pressed during the previous
performance
• 0 = no key was pressed
You can then check this status indicator in your program to
determine what action to take next, as shown in line 110 of the
program on the right. Line 11 0 is a test that gives you time to
find and press a different key before the computer continues on to
the next statement.
The following diagrams illustrate the control and function key
codes returned in the various keyboard modes.
K~Y·llnit z 1
AU'I~A
LOCK CTRl
II-88
SPACE
f'iAure 1. ~pllt Keyboard ~can.
Codes returned = athrough 19.
Fr:TN
>NEW
>100 CALL KEY(O,KEY,STATUS)
>110 If STATUS=O THEN 100
>120 NOH=KEY-64
>130
ON NOTE GOTO 250,270,150
,170,190,210,230
>140 GOlD 100
>150 NOH=262
>160 GOlD 280
>170 NOTE=291,
>180 GOlD 280
>190 NOTE=330
>200
GOlD 280
>210 NOTE=31,9
>220 Gala 280
>230 NOTE=392
>240
GOlD 280
>2>0 NOTE-440
>260 GOTO 280
>270 NOTE=494
>280
CALL SOUND(100,NOTE,ZJ
>290 GOTO 100
>RUN
--pLays a different note on
the scaLe as yOu press
the corresponding key (A-G)
(press CLEAR to stop
the procram)
User's Reference Guide

Texas Instruments TI-99/4A Specifications

General

Brand	Texas Instruments
Model	TI-99/4A
Category	Desktop
Language	English