Computer Programming Concepts and Visual Basic David I. Schneider

456 Computer Programming Concepts and Visual Basic
for arrays declared using empty parentheses. Arrays created in procedures use dynamic allocation.
[FILESPEC]: The filespec of a file on disk is a string consisting of the letter of the drive, a
colon, and the name of the file. If directories are being used, the file name is preceded by the
identifying path.
[LINE LABEL]: Program lines that are the destinations of statements such as GoTo and
GoSub are identified by placing a line label at the beginning of the program line or alone on
the line proceeding the program line. Line labels may be placed only at the beginning of a
line, are named using the same rules as variable, and are followed by a colon. Line numbers
may be used in place of line labels, but program readability is greatly improved by using
descriptive line labels.
[RADIANS]: The radian system of measurement measures angles in terms of a distance
around the circumference of the circle of radius 1. If the vertex of an angle between 0 and
360 degrees is placed at the center of the circle, the length of the arc of the circle contained
between the two sides of the angle is the radian measure of the angle. An angle of d degrees
has a radian measure of (pi/180) * d radians.
[SUBROUTINE]: A subroutine is a sequence of statements beginning with a line label and
ending with a Return statement. A subroutine is meant to be branched to by a GoSub statement
and is usually placed after an Exit Sub or Exit Function statement at the bottom of a
procedure so that it cannot be entered inadvertently.
[VARIANT]: Variant is a generic variable type. Any variable that is used without a type declaration
tag ($, %, &, !, #, @) or without being declared as a specific type using an As clause
or a DefType statement is treated as a variant variable. A variable of type Variant can hold
any type of data. When values are assigned to a variant variable, Visual Basic keeps track of
the “type”of data that has been stored. Visual Basic recognizes many types of data: type 0 for
“Empty” (nothing yet has been stored in the variable; the default), type 1 for “Null” (the special
value Null has been assigned to the variable), type 2 for Integer, type 3 for Long integer,
type 4 for Single precision, type 5 for Double precision, type 6 for Currency, type 7 for
Date/time, type 8 for String, type 10 for Error, type 11 for Boolean, and type 17 for Byte. A
single variant variable may be assigned different data types at different points in a program,
although this is usually not a good programming technique. The data assigned to a variant
array need not all be of the same type. As a result, a variant array can be used in much the
same way as a user-defined type to store related data.