Sunday, October 5, 2008

User Operating System Interface

Hello friends in this post i am going to told you about the ways through which an user can interact with the operating system.

There exists two fundamental approaches through which an user can interact with the operating system.First technique is command line interface or command interpreter with the help of which an user can directly enter commands and further these commands are executed by operating system.The second approach is GUI(Graphical User Interface) in which user gets graphical interface to interact with the operating system.Now first begins with command line interface.

Command Line Interface: The main function of the command interpreter is to get and execute the next user-specified command.Many of the commands given at this level manipulate files:create,delete,list,print,copy and so on.The MS_DOS and UNIX shell operate in this way.Now here also exists two ways in which these commands can be implemented.

The first approach implies that, the command interpreter itself contains the code to execute command.For ex: suppose we entered the command 'delete' to delete a file,then in this case the command interpreter jump to a section of code that sets up the appropriate parameter and sets the appropriate system call.The summary of this method is that command interpreter has itself its code for executing the command.

In the second approach whenever users enter any command the command interpreter did not understand the command in any way,what it does, it merely used the command to identify a file to be loaded into memory and executed.This approach is used in UNIX operating system.Thus the UNIX command to create a file is create file.txt. Now the UNIX operating system search for the file create,load the file into memory,and execute it with the parameter file.txt.The function that is associated with the create command would be defined completely by the code in the file create.With the help of this approach an user can add new commands to the system by creating new files with the proper names.