Scroll long instructions on bottom line of screen

This subprocedure can be used when you have a complex program and need to show the user a lot of instructions.

The subprocedure may be called to scroll very long instructions at the bottom of the screen. I placed some text in a string variable named msg$. You can adjust the code to suit your preferences. The instructions may be placed in a text file. The file can be opened and read into the string variable or group of variables if it's longer than 256 characters.

You could put a different message at the bottom of the screen, or place the line telling the user to press a certain key to start the scrolling instructions.

I finished it up by waiting 2 seconds and replacing the bottom line with the beginning of the message. You could simply blank it out after a short wait, or put back the notice for the user to press a certain key to scroll the instructions again.

Notice that I used double parentheses around the ((msg$)) argument to call the sub. This passes the msg$ variable By Value instead of By Reference. It keeps the original value of the message and prevents it from becoming corrupted or growing longer with each new repeat.

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DECLARE SUB Scroll (msg AS STRING)
DIM msg AS STRING
msg$ = "This is a very long message that will scroll around. It will serve as instruction for using a software program and should stay on the bottom line. "
CLS
LOCATE 25, 1
PRINT LEFT$(msg$, 80);
DO
    LOCATE 1, 1
    PRINT "Press any key to display the scrolling instruction line; Esc to end"
    E$ = INPUT$(1)
    IF E$ <> CHR$(27) THEN CALL Scroll((msg$))
LOOP UNTIL E$ = CHR$(27)
END

SUB Scroll (msg AS STRING)
DIM startmsg AS STRING
DIM N AS INTEGER
N = LEN(msg)
DIM ch AS STRING
DIM circuit AS INTEGER
circuit = 0
startmsg$ = msg$
VIEW PRINT 25 TO 25
DO
    circuit = circuit + 1
    ch = MID$(msg$, 1, 1)
    msg$ = MID$(msg$, 2, N - 1) + ch
    PRINT LEFT$(msg$, 80);
    pause = .1
    t = TIMER
    DO WHILE t + pause >= TIMER: LOOP
LOOP UNTIL circuit = N - 80
DO WHILE t + 2 >= TIMER: LOOP
PRINT LEFT$(startmsg$, 80);
VIEW PRINT
END SUB