Computer Operating System (OS) is an interface between the user and computer hardware and other software. It is the collection of programs that helps the user to manage the computer hardware.The software that allows computer users to run applications with the hardware.
Concepts
OS is the most important program that runs on a computer. Every computer must have an operating system to run other programs andapplications.
An operating system performs such tasks like memory allocation, controlling input &output devices.
Without OS computer doesn’t work. There are many OS’s on which it can perform different tasks Windows OS, mac OS, and Linux.
Types of operating systems
Based on different uses and nature of operating systems are classified into several types:
Single and multi-tasking
Single and multi-user
Distributed
Network Operating system
Real-time
Mobile Operating system
Single and multi-tasking: A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program parallel. This is done by sharing processor to multiple processes at the same time.
Single and multi-user: A single-user operating system is a system in which only one user can access the computer system at a time. On the other hand, a multi-user operating system allows more than one user to access a computer system at one time.
Distributed: A distributed operating system connects a group of different computers and makes them appear to be a single computer. When program may be run on any computer in the distributed system and access data on any other computer. All these computers connected by the networking.
Network Operating system: A network operating system includes special functions for connecting computers and devices into a local-area network (LAN). Some operating systems, such as UNIX and the Mac OS, have networking functions built in.
Real-time Operating Systems: are very fast and quick respondent systems. These systems are used in an environment where a large number of events (generally external) must be accepted and processed in a short time. Most of the time, processes remain in primary memory in order to provide a quick response.
Mobile Operating system: A mobile operating system (OS) is software that allows smartphones and other devices to run applications and programs. Examples of mobile device operating systems include Apple iOS, Google Android BlackBerry OS, Nokia’s Symbian etc.
Functions of Operating Systems
Some important functions of operating system are
Program execution: OS acts as an interface between application software and the hardware. It allocates the memory and other resources which need to execute the program.
Interrupts: It is a type of signal from the computer when it requires the operating system to stop the process and it says what to do next to complete the process. There are two types of Interrupts software interrupts and hardware interrupts
Memory Management: It is the most important task in the operating system. It keeps track of each and every memory location, either it is allocated to some process or it is free. It checks how much memory is to be allocated to processes. It tracks whenever some memory gets free or unallocated then it updates the status.
Virtual memory: Virtual Memory is a space where large programs can store themselves in form of pages while their execution and only the required pages are loaded into the main memory. This technique is useful when large virtual memory is required for user programs when a very small physical memory (hard disk memory) is there.
Networking: Modern operating systems are supporting different types networking protocols. This means when different computers running different operating systems can participate in a common network for sharing resources such as printers, scanners, files.
Security: OS security refers to required steps or measures used to protect the OS from threats, viruses, worms, malware or remote hacker intrusions. OS security takes care of all preventive-control techniques, which safeguard any computers data or information are being stolen, edited or deleted if OS security is compromised.
Disk access and file system: Access to data stored in the disk is a major feature in all operating systems. Computer store data in disk using files, which are structured in a specific way in order to allow faster access, higher reliability and give the better experience to the user.
Input/output management: OS manages I/O devices and makes the I/O process effectively. OS accepts the input from the input devices and stores in the main memory, asks to process it and finally, the provides the results to the output devices for output.
Time Sharing: Every time CPU tries to manage the time. It shares the resources to all the processes which are currently running. Distributes the time to the one which is on high priority.