Computer Programming Concepts and Visual Basic David I. Schneider

■ USING TEXT BOXES FOR INPUT AND OUTPUT
The contents of a text box is always a string. Therefore, statements such as
and
strVar = txtBox.Text
txtBox.Text = strVar
can be used to assign the contents of the text box to the string variable strVar and vice versa.
Numbers are stored in text boxes as strings. Therefore, they should be converted to numbers
before being assigned to numeric variables. If str is a string representation of a number,
then
Val(str)
is that number. Conversely, if num is a number, then
Str(num)
is a string representation of the number. Therefore, statements such as
and
numVar = Val(txtBox.Text)
txtBox.Text = Str(numVar)
can be used to assign the contents of the text box to the numeric variable numVar and vice versa.
Note: When a non-negative number is converted to a string with Str, its first character (but not
its last character) is a blank space.
EXAMPLE 6
The following program converts miles to furlongs and vice versa. Note: A furlong is 1/8th of a mile.
Object Property Setting
frm3_4_6 Caption, Convertor
lblMile Caption Miles
txtMile Text 0
lblFurlong Caption Furlongs
txtFurlong Text 0
The two text boxes have been named txtMile and txtFurlong. With the Event procedures shown, typing a
number into a text box and pressing Tab results in the converted number being displayed in the other text
box.
Private Sub txtMile_LostFocus()
txtFurlong.Text = Str(8 * Val(txtMile.Text))
End Sub
Private Sub txtFurlong_LostFocus()
txtMile.Text = Str(Val(txtFurlong.Text) / 8)
End Sub
■ ANSI CHARACTER SET
Each of the 47 different keys in the center typewriter portion of the keyboard can produce two
characters, for a total of 94 characters. Adding 1 for the space character produced by the space
bar makes 95 characters. These characters have numbers ranging from 32 to 126 associated with
Strings 45