Captive user interface

A captive user interface or CUI is a style of interaction with an application that exists outside the scope of the highest level command interpreter present on the system.Once you invoke an application from command interpreter , it is not possible to communicate with the command interpreter until the application exists.

Ex :
$ mail command  for mailing
;;
$ exit
$ grep(searching) command
;;
$

Kernel functions

Kernel functions
Kernel is core of the Linux O.S.This interacts with the hardware.It  is loaded into the memory when a system is booted.
Functions
Managing the system resources
Allocating time for users and processes
Deciding process priorities and performing them

Structure of Linux System (Layered view of Linux O.S)

The X Window System

The X Window System

• Another important component of Linux is its graphical user interface, the X Window System. Unix was originally a mouseless, text-based system that used noisy teletype machines rather than modern CRT monitors. The Unix command interface is very sophisticated and, even today, some power users prefer it to a point-and-click graphical environment, using their CRT monitor as though it were a noiseless teletype. Consequently, some remain unaware that Unix long ago outgrew its text-based childhood, and now provides users a choice of graphical or command interfaces.

• X is a unique graphical user interface in two major respects. First, X integrates with a computer network, letting users access local and remote applications. For example, X lets you open a window that represents an application running on a remote server: the remote server does the heavy-duty computing; all your computer need do is pass the server your input and display the server's output.

• Second, X lets you configure its look and feel to an amazing degree. To do so, you run a special application - called a window manager - on top of X. A variety of window managers is available, including some that closely mimic the look and feel of Microsoft Windows.

Features of linux

•  The X Window system : X window system provides the foundation for the GUI available with Linux. (Windows feel and look).A user can  interact with computer through multiple windows on screen(Win look and feel).

• With the new version of linux, networking system has been made more reliable.Linux networking supports many valuable utilities that allow the user to access remote systems over a variety of networks.Can access files on disks mounted on other systems and also one user’s file accessible to other users.programs could be run on the machine and results will be displayed on another machine.

•  Linux is rich in its software development environment. Many computer languages have interpreters and compilers. Ex Ada,Pascal,C..Etc

•  Email programs common with linux are   mail,pine,mh,xmh,exmh,netscape mail and elm. These mail programs allow us to send and receive encoded binay messages. 

Modularity

Modularity is designing a system that is divided into a set of functional units (named modules) that can be composed into a larger application. A module represents a set of related concerns

 

online banking program

 

• Transferring money  between accounts

• Paying bills

• updating Personal information.

• Depositing

Functions

•Functions

• Command interpreter: The os interprets the command typed in by the user and translates it to the machine language.Then translates the result of a command into the user understandable language(HLL).Command Interpretation.

• Peripheral manager: os manages the devices attached to its system.(I/O devices).the task of accepting input and producing the output is managed by OS(peripheral management)

• Memory manager: (multi process)many processes are running which require memory from CPU.The decision to allocate a certain amount of memory for a particular process is done by os.(memory mangt)

•

• process manager: There might be different processes running simultaneously. Time spent on a process by the CPU is done by OS(process mangt)