Instant TI RUNs
Quite awhile ago I read about a command for the TI-99/4A which causes a program to RUN instantly after you hit ENTER. I looked through many books and articles and did not find this information. Can you help?
It sounds like you are describing the pre-scan commands available with Extended BASIC. These commands (!@P—and !@P + ) are documented on pages 7 through 10 in the Addendum of the TI Extended BASIC Manual.
When you enter RUN on the TI, there is a brief pause before the program executes. During this pause (most evident with long programs), the computer "pre-scans" the program and sets aside memory for variables, arrays, and data.
Only certain instructions in a TI BASIC program require pre-scanning. These include the first DATA statement, the first use of each variable and/or array, the first reference to each CALL statement of any subprogram, all DEF statements (for user-defined functions), and all SUB and SUBEND statements (and any variables introduced in the user-defined subprogram). So, rather than pre-scanning an entire program, you can pre-scan only part of it by appropriately positioning the pre-scan commands (!@P + to turn pre-scan on and !@P—to turn it off). in many cases, this greatly reduces the initial pause.
Although you can scatter the pre-scan commands throughout your program where necessary, there is a more efficient way to use this option. Simply collect all the statements you want pre-scanned on one line without regard to syntax and place a GOTO at the beginning of the line. This prevents the other statements on the line from executing during the program run. Here's an example of this technique:
100 DATA 5 110 GOTO 120 :: I :: X :: Y :: Z :: CALL CLEAR :: CALL SCREEN :: CALL CHAR :: CALL HCHAR :: CALL VCHAR :: !@P- 120 CALL CLEAR :: CALL SCREEN (14) 130 CALL CHAR (97, "FFFF0000FFFF0000") 140 READ X :: FOR I = 1 TO X :: CALL HCHAR (X + I, 10, 97, X) :: CALL VCHAR (15, X + I, 97, X) :: NEXT I 150 READ Y, Z 160 DATA 10, 20 170 DISPLAY AT (20, 5) : Y, Z 180 FOR I = 1 TO 1000 :: NEXT I
For other examples using these commands, consult the Extended BASIC Manual Addendum.