List and describe the four main resources that an operating system manages (CPU, Memory, Storage, Peripherals)

    A system resource is any usable part of a computer that can be controlled and assigned by the operating system so all of the hardware and software on the computer can work together as designed.

Operating system (OS), program that manages a computer’s resources, especially the allocation of those resources among other programs. Typical resources include the central processing unit (CPU), computer memory, file storage, input/output (I/O) devices, and network connections. Management tasks include scheduling resource use to avoid conflicts and interference between programs. Unlike most programs, which complete a task and terminate, an operating system runs indefinitely and terminates only when the computer is turned off.

    OS Management Functions. Although the range of services and value-added features provided by a modern operating system is continually growing, there are four fundamental operating system management functions that are implemented by all operating systems. Each of these management functions is briefly described below in order to provide an overall context for what follows. The four main operating system management functions (each of which will be dealt with in greater depth elsewhere) are:

    Process management. The term process refers here to program code that has been loaded into a computer's memory so that it can be executed by the central processing unit (CPU). In a multiprogramming system, there will be a number of competing processes. The operating system must ensure that each process gets a fair share of the CPU's time. Before a program can be executed, at least part of the program's executable code must be loaded into memory as a process. The operating system must then determine when the CPU can be made available to the process, and for how long. Once a process controls the CPU, its instructions will be executed until its allotted time expires, or until it terminates, or until it requests an input or output operation. In the latter case, the operating system will service the I/O request and suspend the execution of the process until the I/O request has been satisfied, and the CPU is once more available. In order to be able to schedule the execution of multiple processes, the operating system must maintain a significant amount of information about each process, including the location of the process in memory, the current state of the process (i.e. running, ready, or blocked), the address of the last program instruction executed, and whether or not the process is awaiting the completion of an I/O operation.

    Memory Management. All computers have random access memory, or RAM. Unlike hard drive storage, which is relatively permanent, RAM is what remembers everything you're doing in the moment. If you have a browser, photo editor, music program, and messaging application open, all of your progress and the status of each are stored in the RAM. The operating system works with your RAM sticks to control how much memory is used by each application, including the OS itself.

    Secondary storage management. All applications require disk storage – if only to store the application software itself. The OS provides the common access routines to the secondary disk storage devices. It will keep track of data and program file names, physical locations and perform common functions such as the copying, erasing or backing up of data. It also makes the differences in physical hardware as transparent as possible: a data file will appear the same to an application whether the data is being loaded from a diskette, a hard disk or an optical CD-ROM.

    Peripheral handler. Apart from managing the memory and secondary storage devices, the OS is usually also responsible for the handling of other peripheral devices. Again, a major objective is to relieve the application from the responsibility of having to cater for a multitude of different possible input and output devices. Thanks to the OS, a program (developer) does not need to cater for the differences between a trackball, mouse or other pointing device. The OS will also ensure that your document will be printed correctly, regardless of whether you have a colour inkjet, a laser or lowly dot-matrix printer attached. Equally, individual programs no longer have to worry about the resolution or capability of your computer monitor. The critical element is again that the applications do not have to worry about the actual hardware connected to the computer system. This is usually achieved by means of device drivers, small software routines that become part of the operating system and help it to interface correctly with specific hardware devices. The device drivers for popular or standard devices are usually already included in the operating system.