3.3.1.1 The Main Features of Operating Systems Describe the main features of operating systems, for example memory management, and scheduling algorithms.

Different types of operating systems: Batch OS Interactive OS An operating system is the core software that allows a computer to run as an useful device, it manages the hardware, the user interface and all other software running on the computer. Different types of operating systems: Batch OS Interactive OS Real-time OS Network OS Multiuser OS Multiprogramming OS Multitasking OS

Types of Operating Systems (OS) Definition Example of Use Batch OS Data or programs are collected grouped and processed at a later date. Payroll, stock control and billing systems. Interactive OS Allows the user and the computer to be in direct two-way communication Select from a menu at ATM. Real-time OS Inputs immediately affect the outputs. Timing is critical Control of nuclear power plants, air traffic control systems. Network OS Allow a computer on a network to serve requests from other computers for data and provide access to other resources such as printer and file systems. Manage simultaneous access by multiple users Multiuser OS Handle many people running their programmes on the computer at the same time A number of terminals communicating with a central computer which allocates processing time to each terminal in turn. Multiprogramming OS Ability to run many programmes apparently at the same time. Mainframe systems. Each job is allocated a small amount of processing time (time slice) in turn. Multitasking OS The ability to hold several programmes in RAM at one time but the user switches between them. Usually uses GUI’s. Facilitates import and export of data.

Parts of an operating system Kernel This has the task of loading the applications into memory, making sure they do not interfere with one another and allowing them to share use of the CPU efficiently. The kernel also handles file storage to and from secondary storage Device Drivers Every piece of hardware that makes up the computer or connected to it, will have a device driver that allows the operating system to control and communicate with it. User Interface This part of the operating system is directing what you see on the screen (via the device driver) and reacting to your key presses and other inputs. The user interface could be a basic command line interface (CLI) or a Graphical User Interface (GUI) System Utilities This part of the operating system provides all the basic facilities that run in the background without user interaction. For example print spool services and cryptographic password management.

Function of an operating system No matter what type of computer (or computing device) an operating system is controlling, all operating systems are responsible for the following: • memory management • file management • input and output management • processor time management (scheduling) • providing the human/computer interface • providing system services such as printing spooling • handling all types of error while doing the above.