What are the three main purposes of an operating system? Explain how the old mainframe computers were different from the computers we have today.

(1) To manage the computer's resources, which includes central processing unit, memory, disk drives, and printers, (2) To establish a user interface

(3)To execute and provide services for applications software.

The old mainframe computers have

(1) low memory sizes

(2) slower connectivity speed

(3) Larger sizer

(4) low sophistication.

Explanation: Operating system is a system software that manages the computer resources,helps to establish user interface and it helps to provide services for application softwares.

Operating system software includes WINDOWS X,WINDOWS 7,WINDOWS 8,LINUX,etc.

Mainframe computers are computers used by large multinational companies for processing bulk data. Old mainframe computers were produced by IBM(INTERNATIONAL BUSINESS MACHINE) in the year 1952 they are classed two scientific and commercial mainframe computers with different information although they had some incompatibilities. Old mainframe computers are large in size with low processing speed, sophistication and storage compared to present day system.