Page 52 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 3: Using Operating System

Notes
Figure 3.8

3.3.2 Command-Line Interfaces
A CLI (command line interface) is a user interface to a computer’s operating system or an
application in which the user responds to a visual prompt by typing in a command on a specified
line, receives a response back from the system, and then enters another command, and so forth.
The MS-DOS Prompt application in a Windows operating system is an example of the provision
of a command line interface. Today, most users prefer the graphical user interface (GUI) offered
by Windows, Mac OS, BeOS, and others. Typically, most of today’s UNIX-based systems offer
both a command line interface and a graphical user interface.

In the 1980s UNIX, VMS and many others had operating systems that were built this way.
GNU/Linux and Mac OS X are also built this way. Modern releases of Microsoft Windows
such as Windows Vista implement a graphics subsystem that is mostly in user-space; however
the graphics drawing routines of versions between Windows NT 4.0 and Windows Server
2003 exist mostly in kernel space. Windows 9x had very little distinction between the interface
and the kernel.

3.4 Running Programs

One of the most important X features is that windows can come either from programs running
on another computer or from an operating system other than UNIX. So, if your favorite MS-DOS
program doesn’t run under UNIX but has an X interface, you can run the program under MS-
DOS and display its windows with X on your UNIX computer. Researchers can run graphical
data analysis programs on supercomputers in other parts of the country and see the results in
their offices.
3.4.1 Setting Focus
Of all the windows on your screen, only one window receives the keystrokes you type. This
window is usually highlighted in some way. By default in the mwm window manager, for
instance, the frame of the window that receives your input is a darker shade of grey. In X jargon,

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