IB Computer Science - Features of the interface provided by the OS

Features of Interfaces Provided by the OS

Common features of applications

[Application software ]

a software created for specific purpose or developed to help users perform specific tasks. Includes database programs, word processors, spreadsheets, multimedia editing software, etc.

Features

Toolbars

- Is a graphical control element of which on-screen buttons, icons, menus or other input or output elements are placed.
- Are seen in many types of applications such as office suites, graphics editors and web browsers.

Menus

- Is a graphical control element.
- Is a list of options or commands presented to a user through an interface.
- In a CLI:
  - Simple text menus offer options that can be selected using the keyboard.
- In a GUI:
  - Is a row or strip of menu items titles that, when clicked, display drop-down menus of other items or commands.
  - Is an integral GUI component for a variety of software applications.
  - A context menu appears upon user interaction e.g. a right-click mouse operation.
    - It offers a limited set of choices that are available in the current state, or context, of the operating system or application.

Dialog boxes

- Is a new window that appears above the rest that lists additional information, errors or options.
- It communicates information to the user and prompts them for a response.
- Are classified as “modal” because they block interaction with the software until a response is made.

GUI layout containers

- GUIs use a variety of controls to interact with the user.
- These controls are displayed in different ways according to the layout container used by an application.
- Are usually nested inside other containers to create complex layouts.

Layout container

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Description

A control element is given exact x and y coordinates of where it appears. These coordinates are measured from the top left hand corner of the pane. They are less useful when the window is resized because the controls do not adjust their position on the screen.

Divides the window into top, left, right, bottom and center regions into which controls or other containers can be placed.

Creates a tabular layout with rows and columns. This is often used for forms because it makes it possible to line up controls vertically and horizontally.

Is used to place (stack) content on top of other content. E.g. if text was to be placed on top of an image control, this could be done.

GUI container organizers

Some containers are designed specifically to organize how a group of layout containers are displayed.

Container organizer

Description

Can display several other containers. Only one of them is displayed at once, and the user can change the displayed bane by clicking on the horizontal title bars for each container in the “accordion”. There, transition between containers is usually accompanied by a slide animation.

Can display several other containers. Only one of them is displayed at once, and the user can change between containers by clicking on the tabs at the top.

Is used to display two layout containers at once with an (often movable) separator between them. This can be done either vertically or horizontally.

GUI control elements

A graphical control element or widget is an element of content display or interaction with the user, such as a button or label.

Widget

Description

A control that accepts single line of use text input.

A control that accepts single line of use text input. Unlike the TextField, the characters entered are not visible to the user, instead they appear as either asterisks or circles.

A control that accepts multiple lines of use text input.

A control that is used to display text in an interface. The text is often used to describe another control.

A control which can be clicked upon to perform an action.

Also called a drop-down list. It is a list of items from which to select. The list normally only displays items when a special button or indicator is clicked.

OS provided interfaces

- Implementations of widgets are often packaged together in toolkits, which programmers use to build GUIS.
- All major OSs provide a collection of UI components; these are a set of ready-to-tailor widgets that a programmer can incorporate in an application.
- Each widget is defined as a class in an object-oriented programming (OOP) language.
- Thus many widgets are usually derived from a hierarchy of class inheritance.

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