An operating system acts as an intermediary between the user of a computer and the computer hardware. An Operating System (OS) is a software that manages the computer hardware.
- Hardware: It provides the basic computing resources for the system. It consists of CPU, memory and the input/output (I/O) devices.
- Application Programs: Define the ways in which these resources are used to solve user's computing problems. e.g., word processors, spreadsheets, compilers and web browsers.
Components of a Computer System
- Process Management: The operating system manages many kinds of activities ranging from user programs to system programs like printer spooler, name servers, file server etc.
- Main-Memory Management: Primary-Memory or Main-Memory is a large array of words or bytes. Each word or byte has its own address. Main-memory provides storage that can be accessed directly by the CPU. That is to say for a program to be executed, it must be in the main memory.
- File Management: A file is a collected of related information defined by its creator. Computer can store files on the disk (secondary storage), which provides long term storage. Some examples of storage media are magnetic tape, magnetic disk and optical disk. Each of these media has its own properties like speed, capacity, data transfer rate and access methods.
- I/O System Management: I/O subsystem hides the peculiarities of specific hardware devices from the user. Only the device driver knows the peculiarities of the specific device to whom it is assigned.
- Secondary-Storage Management: Secondary storage consists of tapes, disks, and other media designed to hold information that will eventually be accessed in primary storage (primary, secondary, cache) is ordinarily divided into bytes or words consisting of a fixed number of bytes. Each location in storage has an address; the set of all addresses available to a program is called an address space.
- Protection System: Protection refers to mechanism for controlling the access of programs, processes, or users to the resources defined by a computer systems.
- Networking: generalizes network access
- Command-Interpreter System: interface between the user and the OS.
Functions of Operating System
Operating system provides many functions for ensuring the efficient operation of the system itself. Some functions are listed below
- Resource Allocation: Allocation of resources to the various processes is managed by operating system.
- Accounting: Operating system may also be used to keep track of the various computer resources and how much and which users are using these resources.
- Protection: Protection ensures that all access to the system resources is controlled. When several processes execute concurrently, it should not be possible for one process to interface with the other or with the operating system itself.
Operating System Services
Many services are provided by OS to the user's programs.
- Program Execution The operating system helps to load a program into memory and run it.
- I/O Operations Each running program may request for I/O operation and for efficiency and protection the users cannot control I/O devices directly. Thus, the operating system must provide some means to do I/O operations.
- File System Manipulation Files are the most important part which is needed by programs to read and write the files and files may also be created and deleted by names or by the programs. The operating system is responsible for the file management.
- Communications Many times, one process needs to exchange information with another process, this exchange of information can take place between the processes executing on the same computer or the exchange of information may occur between the process executing on the different computer systems, tied together by a computer network. All these things are taken care by operating system.
- Error Detection It is necessary that the operating system must be aware of possible errors and should take the appropriate action to ensure correct and consistent computing.
Types of Operating Systems
The Operating system can perform a Single Operation and also Multiple Operations at a Time. So there are many types of Operating systems those are organized by using their Working Techniques.
- Serial Processing: The Serial Processing Operating Systems are those which perform all the instructions in a Sequence Manner or the Instructions those are given by the user will be executed by using the FIFO Manner means First in First Out. Mainly the Punch Cards are used for this. In this all the Jobs are firstly Prepared and Stored on the Card and after that card will be entered in the System and after that all the Instructions will be executed one by One. But the Main Problem is that a user doesn’t interact with the System while he is working on the System, means the user can not be able to enter the data for Execution.
- Batch Processing: The Batch Processing is same as the Serial Processing Technique. But in the Batch Processing Similar Type of jobs are Firstly Prepared and they are Stored on the Card and that card will be submitted to the System for the Processing. The Main Problem is that the Jobs those are prepared for Execution must be the Same Type and if a job requires for any type of Input then this will not be Possible for the user. The Batch Contains the Jobs and all those jobs will be executed without the user Intervention.
- Multi-Programming: Execute Multiple Programs on the System at a Time and in the Multi-programming the CPU will never get idle, because with the help of Multi-Programming we can Execute Many Programs on the System and When we are Working with the Program then we can also Submit the Second or Another Program for Running and the CPU will then Execute the Second Program after the completion of the First Program. And in this we can also specify our Input means a user can also interact with the System.
- Real Time System: In this Response Time is already fixed. Means time to Display the Results after Possessing has been fixed by the Processor or CPU. Real Time System is used at those Places in which we Require higher and Timely Response.
- Hard Real Time System: In the Hard Real Time System, Time is fixed and we can’t Change any Moments of the Time of Processing. Means CPU will Process the data as we Enters the Data.
- Soft Real Time System: In the Soft Real Time System, some Moments can be Change. Means after giving the Command to the CPU, CPU Performs the Operation after a Microsecond.
- Distributed Operating System: Distributed Means Data is Stored and Processed on Multiple Locations. When a Data is stored on to the Multiple Computers, those are placed in Different Locations. Distributed means In the Network, Network Collections of Computers are connected with Each other. Then if we want to Take Some Data From other Computer, Then we use the Distributed Processing System. And we can also Insert and Remove the Data from out Location to another Location. In this Data is shared between many users. And we can also Access all the Input and Output Devices are also accessed by Multiple Users.
- Multiprocessing: In the Multi Processing there are two or More CPU in a Single Operating System if one CPU will fail, then other CPU is used for providing backup to the first CPU. With the help of Multi-processing, we can Execute Many Jobs at a Time. All the Operations are divided into the Number of CPU’s. if first CPU Completed his Work before the Second CPU, then the Work of Second CPU will be divided into the First and Second.
- Parallel operating systems: These are used to interface multiple networked computers to complete tasks in parallel. Parallel operating systems are able to use software to manage all of the different resources of the computers running in parallel, such as memory, caches, storage space, and processing power. A parallel operating system works by dividing sets of calculations into smaller parts and distributing them between the machines on a network.
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