After BASIC executes all of the statements in the loop, it adds z to x and then checks to see if this sum is greater than y. How many times BASIC loops through these statements is controlled by the FOR command. When BASIC encounters a FOR-NEXT loop, it executes all of the statements between the FOR and the NEXT. The FOR-NEXT statement allows us to create a loop that accomplishes a lot of work and has an ending. They are only problems if they are never-ending loops. When we last discussed loops, they were viewed as problems. Now look at the statements on either side of the SOUND. Since the computer counts 18 clock ticks every second, a duration of 1 would be 1/18 of a second. It has a variable in the frequency field and a duration of. We can replace the frequency and duration numbers with variable names! Then using the BASIC FOR-NEXT statement we can let our program change the contents of the variables. This is where variables come to our rescue.

If you entered the DOREMI program you can probably see that writing individual SOUND statements is time consuming. Experiment with other frequencies and durations. In this case, a 1,000 Hz tone will play for one second. Here is how the command is written in a BASIC program: If you want a one-half second sound, divide 18 by two. Therefore, if you want a sound to last one second, specify a duration of 18. This is specified in personal computer clock ticks rather than some ordinary unit like seconds. How long the sound plays is called the duration. Since the little speaker inside your personal computer is not a terribly high quality device, the practical upper limit is about 16,000 Hz. Under the best conditions, the highest value a human can hear is around 18,000 Hz. The highest frequency you can specify is well above human hearing. The lowest tone BASIC can sound is 37 Hz. The frequency is specified in Hertz (Hz) or cycles per second. Just specify the frequency, or pitch, of the tone along with how long it should last. Along the way, we will learn some new ways to control the running of programs. Your personal computer can make music.Д«ASIC includes the SOUND statement which allows your program to produce sounds as output! In this chapter we will explore SOUND, making fun noises as well as real music. Yet, despite their cost, complexity, and power, your personal computer can do something these machines cannot. One hundred feet from my office is a computer room filled with IBM computers worth some fifty million dollars.

Gw basic nested loop programs