Using Subroutines - Lesson 3

The first two lessons show how to write old style BASIC programs which use GOTO. Let's show how to create the hypotenuse calculator in a more structured way using scoped subroutines. Here is the code:

'hypotenuse calculator
global a, b, c, #sideA, #sideB
call displayAll
wait

sub displayAll
cls
print "Hypotenuse Calculator"
print
print "Length of side A: ";
textbox #sideA, a
print
print "Length of side B: ";
textbox #sideB, b
print
button #go, "Go!", computeSideC
print
if c > 0 then print "Length of side C: "; c
end sub

sub computeSideC key$
a = #sideA value()
b = #sideB value()
c = sqr(a^2+b^2)
call displayAll
end sub

If you compare this example to the one for lesson 2, you'll see most of the code is the same.

• The first few lines of code kick the program off by calling the displayAll subroutine.
• The displayAll subroutine adds a button which calls the computeSideC subroutine when it is clicked.
• The computeSideC subroutine does some math and then calls the displayAll subroutine, forcing the web page to update.

Web Programming without Web Programming

This blog will include short lessons that show how to do many different things in Run BASIC, a web programming so easy that it's fair to call it "Web Programming without Web Programming." I call it this because web programming is hard, but Run BASIC is not hard.