Aashish Vats.

* operating system  Operating system is a system software. Which is used to operate a computer. It provide a interface between user and machine.its may enable to computer hardware. In other word we can say that its interact with computer hardware and some software. Its provide a platform to implement another software. So it is called system software. On the basis of user site operating system divided into three types * single user single tasking * single user multi tasking * multi user multi tasking  Single user single tasking_- In this type of operating system a single user can create a single task in a same time..it is only design for using personal computer.. Ex- dos.

* The development of computer has been very rapid in sixty year.the development has been disting in five stages. Each stage is called computer generation. *first generation 1946 to 1955 *second generation 1955 yo 1965 *third generation 1965 to 1975 * fourth generation 1975 to 1990 * fifth generation 1990 to yet

* Doskey command  This command is used to create a shutcut command instead of dos Dos command.. *example C=cls.. *cls command This command is used to clear a screen. If we create doskey command of cls Than c= cls Therefore we enter c than screen is clear. In doskey command we only create some shutcut command. Like- date,time and cls But now a time one question arise in my mind.. Why we not create another doskey command??accept date,time and cls?