is a set of programs that manages the computer's hardware
devices and controls their processes. Application software refers to programs that
make the computer useful to the user. These programs solve specific problems, or
perform general operations that satisfy the needs of the user. Word processing,
spreadsheet, and database packages are all examples of application software.
refers to the way of designing programs around
procedures (rather than objects). A procedure is a named sequence of executable
is centered on creating objects. An object is a
programming element that contains data (attributes) and actions. In Visual Basic,
an object's attributes are called
. The actions that an object performs are
. The object is, conceptually, a self-contained unit consisting of
data (properties) and actions (methods).
respond to events. An event is an action that takes place,
such as the clicking of a button with the mouse. When an event occurs, the
application responds by executing a special type of method known as an event
Although GUIs have made programs friendlier and easier to interact with, they
have not simplified the task of programming. GUIs make it necessary for the
programmer to create a variety of on-screen elements such as windows, dialog
boxes, buttons, menus, and other items. Each of these on-screen elements can be
modeled in software by an object.
A Label control is used to display text information. The user cannot enter a value
into a Label control, or change the value it displays. The user can, however, enter
information into a TextBox control. It is appropriate to use a Label control when
displaying data that the user cannot change. It is appropriate to use a TextBox
control when the user must enter data.
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