Course : CSC204

CSC204, 2.1 Types of Operatign System User Interface

The User Interface

Graphical User Interfaces (GUIs)

GUI Tools

Applications and the Interface

Menus

Dialog Boxes

Command-Line Interfaces

The User Interface
- Graphical User Interfaces (GUIs)

Most modern operating systems, like Windows and the Macintosh OS, provide a graphical user interface (GUI).

A GUI lets you control the system by using a mouse to click graphical objects on screen.

A GUI is based on the desktop metaphor. Graphical objects appear on a background (the desktop), representing resources you can use.

The User Interface - GUI Tools

Icons are pictures that represent computer resources, such as printers, documents, and programs.

You double-click an icon to choose (activate) it, for instance, to launch a program.

The Windows operating system offers two unique tools, called the taskbar and Start button. These help you run and manage programs.

The User Interface –
Applications and the Interface

Applications designed to run under one operating system use similar interface elements.

Under an OS such as Windows, you see a familiar interface no matter what programs you use.

In a GUI, each program opens and runs in a separate window—a frame that presents the program and its documents.

In a GUI, you can run multiple programs at once, each in a separate window. The application in use is said to be the active window.

The User Interface - Menus

GUI-based programs let you issue commands by choosing them from menus.

A menu groups related commands. For example, the File menu's commands let you open, save, and print document files.

Menus let you avoid memorizing and typing command names.

In programs designed for the same GUI, menus and commands are similar from one program to another.

The User Interface - Dialog Boxes

A dialog box is a special window that appears when a program or the OS needs more information before completing a task.

Dialog boxes are so named because they conduct a "dialog" with the user, asking the user to provide more information or make choices.

The User Interface - Command-Line Interfaces

Some older operating systems, such as DOS and UNIX, use command-line interfaces.

In a command-line interface, you type commands at a prompt.

Under command-line interfaces, individual applications do not need to look or function the same way, so different programs can look very different

CSC204, 2.1 Types of Operatign System User Interface

Command-line interface

Command-line interface
http://en.wikipedia.org/wiki/Command-line_interface

A command-line interface (CLI) is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks. This text-only interface contrasts with the use of a mouse pointer with a graphical user interface (GUI) to click on options, or menus on a text user interface (TUI) to select options. This method of instructing a computer to perform a given task is referred to as "entering" a command: the system waits for the user to conclude the submitting of the text command by pressing the "Enter" key (a descendant of the "carriage return" key of a typewriter keyboard). A command-line interpreter then receives, analyses, and executes the requested command. The command-line interpreter may be run in a text terminal or in a terminal emulator window as a remote shell client such as PuTTY. Upon completion, the command usually returns output to the user in the form of text lines on the CLI. This output may be an answer if the command was a question, or otherwise a summary of the operation.

The concept of the CLI originated when teletypewriter machines (TTY) were connected to computers in the 1950s, and offered results on demand, compared to batch oriented mechanical punched card input technology. Dedicated text-based CRT terminals followed, with faster interaction and more information visible at one time, then graphical terminals enriched the visual display of information. Currently personal computers encapsulate all three functions (batch processing, CLI, GUI) in software.

The CLI continues to co-evolve with GUIs like those provided by Microsoft Windows, Mac OS and the X Window System. In some applications, such as MATLAB and AutoCAD, a CLI is integrated with the GUI, with some benefits of both.

Usage

A CLI is used whenever a large vocabulary of commands or queries, coupled with a wide (or arbitrary) range of options, can be entered more rapidly as text than with a pure GUI. This is typically the case with operating system command shells. Also, some computer languages (such as Python, Forth, LISP and many dialects of BASIC) provide an interactive command-line mode to allow for experimentation.

CLIs are often used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users. CLIs are also popular among people with visual disability, since the commands and feedbacks can be displayed using Refreshable Braille displays.

A program that implements such a text interface is often called a command-line interpreter or shell. Examples include the various Unix shells (sh, ksh, csh, tcsh, bash, etc.), the historical CP/M, and MS-DOS/IBM-DOS's COMMAND.COM, the latter two based heavily on DEC's RSX and RSTS CLIs. (DOS, i.e. MS-DOS/IBM-DOS, is actually is based on CP/M, DOS having been originally written as a substitute for CP/M-86 when its release was delayed.)

In November 2006, Microsoft released version 1.0 of Windows PowerShell (formerly codenamed Monad), which combined features of traditional Unix shells with their object-oriented .NET Framework. MinGW and Cygwin are open-source packages for Windows that offer a Unix-like CLI. Microsoft provides MKS Inc.'s ksh implementation MKS Korn shell for Windows through their Services for UNIX add-on.

The latest versions of the Macintosh operating system are based on a variation of Unix called Darwin. On these computers, users can access a Unix-like command-line interface called Terminal found in the Applications Utilities folder. (This terminal uses bash by default.)
Screenshot of the MATLAB 7.4 command-line interface and GUI.

Some applications provide both a CLI and a GUI. The engineering/scientific numerical computation package MATLAB provides no GUI for some calculations, but the CLI can handle any calculation. The three-dimensional-modelling program Rhinoceros 3D provides a CLI as well as a distinct scripting language. In some computing environments, such as the Oberon or Smalltalk user interface, most of the text which appears on the screen may be used for giving commands.

Anatomy of a shell CLI

A CLI can generally be considered as consisting of syntax and semantics. The syntax is the grammar that all commands must follow. In the case of operating systems (OS), MS-DOS and Unix each define their own set of rules that all commands must follow. In the case of embedded systems, each vendor, such as Nortel, Juniper Networks or Cisco Systems, defines their own proprietary set of rules that all commands within their CLI conform to. These rules also dictate how a user navigates through the system of commands. The semantics define what sort of operations are possible, on what sort of data these operations can be performed, and how the grammar represents these operations and data—the symbolic meaning in the syntax.

Two different CLIs may agree on either syntax or semantics, but it is only when they agree on both that they can be considered sufficiently similar to allow users to use both CLIs without needing to learn anything, as well as to enable re-use of scripts.

A simple CLI will display a prompt, accept a "command line" typed by the user terminated by the Enter key, then execute the specified command and provide textual display of results or error messages. Advanced CLIs will validate, interpret and parameter-expand the command line before executing the specified command, and optionally capture or redirect its output.

Unlike a button or menu item in a GUI, a command line is typically self-documenting, stating exactly what the user wants done. In addition, command lines usually include many defaults that can be changed to customize the results. Useful command lines can be saved by assigning a character string or alias to represent the full command, or several commands can be grouped to perform a more complex sequence — for instance, compile the program, install it, and run it — creating a single entity, called a command procedure or script which itself can be treated as a command. These advantages mean that a user must figure out a complex command or series of commands only once, because they can be saved, to be used again.

The commands given to a CLI shell are often in one of the following forms:

* [doSomething] [how] [toFiles]
* [doSomething] [how] [sourceFile] [destinationFile]
* [doSomething] [how] < [inputFile] > [outputFile]
* [doSomething] [how] | [doSomething] [how] | [do Something] [how] > [outputFile]

doSomething is, in effect, a verb, how an adverb (for example, should the command be executed "verbosely" or "quietly") and toFiles an object or objects (typically one or more files) on which the command should act. The '>' in the third example is a redirection operator, telling the command-line interpreter to send the output of the command not to the screen but to the file named on the right of the '>'. This will overwrite the file. Using '>>' will redirect the output and append it to the file. Another redirection operator is the pipe ('|'), which tells the CLI to use the output of one command as the input to the next command; this "operator-stream" mechanism can be very powerful.

Programming languages in interactive mode

CLI and resource protection

In some CLIs, the commands issued are not coupled to any conceptual place within a command hierarchy. A user can specify relative or absolute paths to any command or data. Examples of this include MS-DOS, Windows, and UNIX, which provide forms of a change directory command which allows access to any directory in the system. In some systems, protection of resources is provided by a system of resource ownership by privileged groups, and password-protected user accounts which are members of specific groups. MS-DOS provides no such resource protection, nor do versions of Windows prior to the Windows NT family. (Both of these were designed as single-user systems, where it was assumed that the owner would simply not allow people that she/he did not fully trust to have physical access to the computer at all. UNIX, by contrast, originated as a time-sharing system in corporate and university environments.)

Other CLIs (such as those in network routers) limit the set of commands that a user can perform to a subset, determined by location within a command hierarchy, grouped by association with security, system, interface, etc. The location within this hierarchy and the options available are often referred to as a mode. In these systems the user might traverse through a series of sub-hierarchies, each with their own subset of commands. For example, if the CLI had two modes called interface and system, the user would enter the word 'interface' at the command prompt and then enter an interface mode, where a certain subset of commands and data are available. At this point system commands are not accessible and would not be accessible until the user explicitly exits the interface mode and enters the system mode.
[edit] Command prompt

A command prompt (or just prompt) is a sequence of (one or more) characters used in a command-line interface to indicate readiness to accept commands. Its intent is to literally prompt the user to take action. A prompt usually ends with one of the characters $, %, #, :, > and often includes other information, such as the path of the current working directory.

On many Unix system and derivative systems, it is common for the prompt to end in a $ or % character if the user is a normal user, but in a # character if the user is a superuser ("root" in Unix terminology).

It is common for prompts to be modifiable by the user. Depending on the environment, they may include colors, special characters, and other elements like the current time, in order, for instance, to make the prompt more informative or visually pleasing, to distinguish sessions on various machines, or to indicate the current level of nesting of commands.

In DOS's COMMAND.COM and in the Windows NT's command-line interpreter cmd.exe the prompt is modifiable by issuing a prompt command or by changing the value of the %PROMPT% environment variable. The default of most modern systems, the C:\> style is obtained, for instance, with "prompt $P$G". The default of older DOS systems, C> is obtained by just "prompt", although on some systems this produces the newer C:\> style; on those systems "prompt $N$G" can be used to switch to the older style.

On many Unix systems, the $PS1 variable can be used, although other variables also may have an impact on the prompt (depending on what shell is being used). In the bash shell, a prompt of the form

[time] user@host: work_dir $

could be set by issuing the command

export PS1='[\t] \u@\H: \W $'

In zsh the $RPROMPT variable controls an optional "prompt" on the right hand side of the display. It is not a real prompt in that the location of text entry does not change. It is used to display information on the same line as the prompt, but right justified.

In RISC OS, the command prompt is a '*' symbol, and thus (OS)CLI commands are often referred to as "star commands"[1]. It is also possible to access the same commands from other command lines (such as the BBC BASIC command line), by preceding the command with a '*'.

CSC204, 2.1 Types of Operatign System User Interface

Graphical user interface

Graphical user interface
http://en.wikipedia.org/wiki/Graphical_user_interface

A graphical user interface (GUI), pronounced gooey,[1] is a type of user interface that allows users to interact with programs in more ways than typing such as computers; hand-held devices such as MP3 players, portable media players or gaming devices; household appliances and office equipment with images rather than text commands. A GUI offers graphical icons, and visual indicators, as opposed to text-based interfaces, typed command labels or text navigation to fully represent the information and actions available to a user. The actions are usually performed through direct manipulation of the graphical elements.[2]

The term GUI is historically restricted to the scope of two-dimensional display screens with display resolutions capable of describing generic information, in the tradition of the computer science research at the Palo Alto Research Center (PARC). The term GUI earlier might have been applicable to other high-resolution types of interfaces that are non-generic, such as videogames, or not restricted to flat screens, like volumetric displays.[3]

History

Precursors

A precursor to GUIs was invented by researchers at the Stanford Research Institute, led by Douglas Engelbart. They developed the use of text-based hyperlinks manipulated with a mouse for the On-Line System. The concept of hyperlinks was further refined and extended to graphics by researchers at Xerox PARC, who went beyond text-based hyperlinks and used a GUI as the primary interface for the Xerox Alto computer. Most modern general-purpose GUIs are derived from this system. As a result, some people[who?] call this class of interface a PARC User Interface (PUI) (note that PUI is also an acronym for perceptual user interface).[4]

Ivan Sutherland developed a pointer-based system called the Sketchpad in 1963. It used a light-pen to guide the creation and manipulation of objects in engineering drawings.
[edit] PARC user interface

The PARC user interface consisted of graphical elements such as windows, menus, radio buttons, check boxes and icons. The PARC user interface employs a pointing device in addition to a keyboard. These aspects can be emphasized by using the alternative acronym WIMP, which stands for windows, icons, menus and pointing device.
[edit] Evolution
The Xerox Star Workstation introduced the first GUI operating systems as shown above.

Following PARC the first GUI-centric computer operating model was the Xerox 8010 Star Information System in 1981,[5] followed by the Apple Lisa (which presented the concept of menu bar as well as window controls) in 1983, the Apple Macintosh 128K in 1984, and the Atari ST and Commodore Amiga in 1985.

The GUIs familiar to most people today are Mac OS X, Microsoft Windows, and X Window System interfaces. Apple, IBM and Microsoft used many of Xerox's ideas to develop products, and IBM's Common User Access specifications formed the basis of the user interface found in Microsoft Windows, IBM OS/2 Presentation Manager, and the Unix Motif toolkit and window manager. These ideas evolved to create the interface found in current versions of Microsoft Windows, as well as in Mac OS X and various desktop environments for Unix-like operating systems, such as Linux. Thus most current GUIs have largely common idioms.

Components

A GUI uses a combination of technologies and devices to provide a platform the user can interact with, for the tasks of gathering and producing information.

A series of elements conforming a visual language have evolved to represent information stored in computers. This makes it easier for people with few computer skills to work with and use computer software. The most common combination of such elements in GUIs is the WIMP ("window, icon, menu, pointing device") paradigm, especially in personal computers.

The WIMP style of interaction uses a physical input device to control the position of a cursor and presents information organized in windows and represented with icons. Available commands are compiled together in menus, and actions are performed making gestures with the pointing device. A window manager facilitates the interactions between windows, applications, and the windowing system. The windowing system handles hardware devices such as pointing devices and graphics hardware, as well as the positioning of the cursor.

In personal computers all these elements are modeled through a desktop metaphor, to produce a simulation called a desktop environment in which the display represents a desktop, upon which documents and folders of documents can be placed. Window managers and other software combine to simulate the desktop environment with varying degrees of realism.

Post-WIMP interfaces

Smaller mobile devices such as PDAs and smartphones typically use the WIMP elements with different unifying metaphors, due to constraints in space and available input devices. Applications for which WIMP is not well suited may use newer interaction techniques, collectively named as post-WIMP user interfaces.[6]

Some touch-screen-based operating systems such as Apple's iOS and Android OS currently use post-WIMP styles of interaction. The iPhone's use of more than one finger in contact with the screen allows actions such as pinching and rotating, which are not supported by a single pointer and mouse.[7]

A class of GUIs sometimes referred to as post-WIMP include 3D compositing window manager such as Compiz, Desktop Window Manager, and LG3D.[citation needed] Some post-WIMP interfaces may be better suited for applications which model immersive 3D environments, such as Google Earth.[8]
[edit] User interface and interaction design
Main article: User interface design

Designing the visual composition and temporal behavior of GUI is an important part of software application programming. Its goal is to enhance the efficiency and ease of use for the underlying logical design of a stored program, a design discipline known as usability. Techniques of user-centered design are used to ensure that the visual language introduced in the design is well tailored to the tasks it must perform.

Typically, the user interacts with information by manipulating visual widgets that allow for interactions appropriate to the kind of data they hold. The widgets of a well-designed interface are selected to support the actions necessary to achieve the goals of the user. A Model-view-controller allows for a flexible structure in which the interface is independent from and indirectly linked to application functionality, so the GUI can be easily customized. This allows the user to select or design a different skin at will, and eases the designer's work to change the interface as the user needs evolve. Nevertheless, good user interface design relates to the user, not the system architecture.

The visible graphical interface features of an application are sometimes referred to as "chrome".[9] Larger widgets, such as windows, usually provide a frame or container for the main presentation content such as a web page, email message or drawing. Smaller ones usually act as a user-input tool.

A GUI may be designed for the rigorous requirements of a vertical market. This is known as an "application specific graphical user interface." Among early application specific GUIs was Gene Mosher's 1986 Point of Sale touchscreen GUI. Other examples of an application specific GUIs are:

* Self-service checkouts used in a retail store
* Automated teller machines (ATM)
* Airline self-ticketing and check-in
* Information kiosks in a public space, like a train station or a museum
* Monitors or control screens in an embedded industrial application which employ a real time operating system (RTOS).

The latest cell phones and handheld game systems also employ application specific touchscreen GUIs. Newer automobiles use GUIs in their navigation systems and touch screen multimedia centers.

Comparison to other interfaces

CLI

GUIs were introduced in reaction to the steep learning curve of command-line interfaces (CLI),[10][11][11] which require commands to be typed on the keyboard. Since the commands available in command line interfaces can be numerous, complicated operations can be completed using a short sequence of words and symbols. This allows for greater efficiency and productivity once many commands are learned,[10][11][11] but reaching this level takes some time because the command words are not easily discoverable and not mnemonic. WIMPs ("window, icon, menu, pointing device"), on the other hand, present the user with numerous widgets that represent and can trigger some of the system's available commands.

WIMPs extensively use modes as the meaning of all keys and clicks on specific positions on the screen are redefined all the time. Command line interfaces use modes only in limited forms, such as the current directory and environment variables.

Most modern operating systems provide both a GUI and some level of a CLI, although the GUIs usually receive more attention. The GUI is usually WIMP-based, although occasionally other metaphors surface, such as those used in Microsoft Bob, 3dwm or File System Visualizer (FSV).

Applications may also provide both interfaces, and when they do the GUI is usually a WIMP wrapper around the command-line version. This is especially common with applications designed for Unix-like operating systems. The latter used to be implemented first because it allowed the developers to focus exclusively on their product's functionality without bothering about interface details such as designing icons and placing buttons. Designing programs this way also allows users to run the program non-interactively, such as in a shell script.

Three-dimensional user interfaces

For typical computer displays, three-dimensional is a misnomer—their displays are two-dimensional. Semantically, however, most graphical user interfaces use three dimensions - in addition to height and width, they offer a third dimension of layering or stacking screen elements over one another. This may be represented visually on screen through an illusionary transparent effect, which offers the advantage that information in background windows may still be read, if not interacted with. Or the environment may simply hide the background information, possibly making the distinction apparent by drawing a drop shadow effect over it.

Some environments use the techniques of 3D graphics to project virtual three dimensional user interface objects onto the screen. As the processing power of computer graphics hardware increases, this becomes less of an obstacle to a smooth user experience.

Motivation

Three-dimensional GUIs are quite common in science fiction literature and movies, such as in Jurassic Park, which features Silicon Graphics' three-dimensional file manager, "File system navigator", an actual file manager that never got much widespread use as the user interface for a Unix computer. In fiction, three-dimensional user interfaces are often immersible environments like William Gibson's Cyberspace or Neal Stephenson's Metaverse.

Three-dimensional graphics are currently mostly used in computer games, art and computer-aided design (CAD). There have been several attempts at making three-dimensional desktop environments like Sun's Project Looking Glass or SphereXP from Sphere Inc. A three-dimensional computing environment could possibly be used for collaborative work. For example, scientists could study three-dimensional models of molecules in a virtual reality environment, or engineers could work on assembling a three-dimensional model of an airplane. This is a goal of the Croquet project and Project Looking Glass.[12]
[edit] Technologies

The use of three-dimensional graphics has become increasingly common in mainstream operating systems, from creating attractive interfaces—eye candy— to functional purposes only possible using three dimensions. For example, user switching is represented by rotating a cube whose faces are each user's workspace, and window management is represented via a Rolodex-style flipping mechanism in Windows Vista (see Windows Flip 3D). In both cases, the operating system transforms windows on-the-fly while continuing to update the content of those windows.

Interfaces for the X Window System have also implemented advanced three-dimensional user interfaces through compositing window managers such as Beryl, Compiz and KWin using the AIGLX or XGL architectures, allowing for the usage of OpenGL to animate the user's interactions with the desktop.

Another branch in the three-dimensional desktop environment is the three-dimensional GUIs that take the desktop metaphor a step further, like the BumpTop, where a user can manipulate documents and windows as if they were "real world" documents, with realistic movement and physics.

The Zooming User Interface (ZUI) is a related technology that promises to deliver the representation benefits of 3D environments without their usability drawbacks of orientation problems and hidden objects. It is a logical advancement on the GUI, blending some three-dimensional movement with two-dimensional or "2.5D" vector objects.