Computer Operating Systems

Introduction: Operating System is a program that acts as an intermediary between a user of a computer and the computer hardware.Main frame operating systems are designed primarily to optimize utilization of hardware. PC operating systems support complex games, business applications etc. Operating systems for handheld computers are designed to provide an environment in which a user can easily interface with the computer to execute programs.

Operating system goals

•Execute user programs and make solving user problems easier

•Make the computer system convenient to use

•Use the computer hardware in an efficient manner. It provided a basis for application programs and acts as an intermediary between the computer user and the computer hardware.

A computer system can be divided roughly into four components – the hardware, the operating system, the application programs and the users.

The hardware – which consists of CPU, memory and I/O devices, provides the basic computing resources for the system.

The application programs define the ways in which these resources are used to solve users’ computing problems.

The operating system controls and co-ordinates the use of hardware among the various application programs for the various users.

Operating System Definition

OS is a resource allocator

• Manages all resources
• Decides between conflicting requests for efficient and fair resource use
• OS is a control program
• Controls execution of programs to prevent errors and improper use of the computer
• No universally accepted definition
• Everything a vendor ships when you order an operating system” is good approximation

But varies wildly

• “The one program running at all times on the computer” is the kernel. Everything else is either a system program (ships with the operating system) or an application program

Operating system from the user view- The user’s view of the computer varies according to the interface being used. While designing a PC for one user, the goal is to maximize the work that the user is performing. Here OS is designed mostly for ease of use. In another case, the user sits at a terminal connected to a mainframe or minicomputer. Other users can access the same computer through other terminals. OS here is designed to maximize resource utilization to assure that all available CPU time, memory and I/O are used efficiently. In other cases, users sit at workstations connected to networks of other workstations and servers. These users have dedicated resources but they also share resources such as networking and servers. Here OS is designed to compromise between individual usability and resource utilization.

Operating system from the system view-From the computer’s point of view, OS is the program, which is widely involved with hardware. Hence OS can be viewed as resource allocator where in resources are – CPU time, memory space, file storage space, I/O devices etc. OS must decide how to allocate these resources to specific programs and users so that it can operate the computer system efficiently. OS is also a control program. A control program manages the execution of user programs to prevent errors and improper use of computer. It is concerned with the operation and control of I/O devices.