Tuning Fork Program

Remember the SOUND statement:

SOUND frequency,duration

In this statement,

• frequency --- is the frequency of the sound in vibrations per second (sometimes called hertz.) It must be more than 37 and less than 32,000 or so.
• duration --- is the length of time to play the sound in clock "ticks". There are about 18 ticks per second.

A previous program in these chapters used a DO...LOOP to repeatedly play a note that the user entered, but it had to be ended by hitting CONTROL-BREAK. This was awkward. Let us re-design the program with a DO WHILE condition so that the loop body is executed only when the user enters a note greater or equal to 37 (in other words, any value less than 37 is a sentinel value.)

' Do repeatedly:
'   Ask the user for a note.
'   Play it for about a second.
'
. . .  do beginning things . . . .
PRINT "Enter the frequency (37-32000):"
INPUT FREQ
DO WHILE FREQ is not a sentinel value

  . . . do something or other  . . . 

  PRINT "Enter the frequency (37-32000):"
  INPUT FREQ
LOOP
. . . ending things  . . .
END

The "beginning things" and the "ending things" blanks do not need to be filled in for this program.