Computer Programming Concepts and Visual Basic David I. Schneider

42 Computer Programming Concepts and Visual Basic
2.4 STRINGS
Two primary types of data can be processed by Visual Basic: numbers and strings. Sentences,
phrases, words, letters of the alphabet, names, telephone numbers, addresses, and social security
numbers are all examples of strings. Formally, a string constant is a sequence of characters
that is treated as a single item. Strings can be assigned names with assignment statements,
can be displayed with Print methods, and can be combined by an operation called concatenation
(denoted by &).
■ VARIABLES AND STRINGS
A string variable is a name used to refer to a string. The allowable names of string variables
are identical to those of numeric variables. The value of a string variable is assigned or altered
with assignment statements and displayed with Print methods just like the value of a numeric
variable.
EXAMPLE 1
The following code shows how assignment statements and Print are used with strings. The string variable
today is assigned a value by the fourth line and this value is displayed by the fifth line. The quotation
marks surrounding each string constant are not part of the constant and are not displayed by the Print
method. (The form design for Examples 1 through 5 consists of a command button and picture box.)
Private Sub cmdButton_Click()
picBox.Cls
picBox.Print “hello”
today = “9/17/99”
picBox.Print today
End Sub
[Run, and then click the command button. The following is displayed in the picture box.]
hello
9/17/99
If x, y, ..., z are characters and strVar1 is a string variable, then the statement
strVar1 = “xy...z”
assigns the string constant xy...z to the variable, and the statement
or
picBox.Print “xy...z”
picBox.Print strVar1
displays the string xy...z in a picture box. If strVar2 is another string variable, then the statement
strVar2 = strVar1
assigns the value of the variable strVar1 to the variable strVar2. (The value of strVar1 will remain
the same.) String constants used in assignment or picBox.Print statements must be surrounded
by quotation marks, but string variables are never surrounded by quotation marks.
As with numbers, semicolons can be used with strings in picBox.Print statements to suppress
carriage returns and line feeds. However, picBox.Print statements do not display leading
or trailing spaces along with strings.