Fundamentals of Operating Systems
Any operating system, such as Windows, Mac or Linux, is an extraordinary program that acts as the layer of brains and intercessor between a user and the computer hardware. The primary function of the operating system is the provision of a smooth management of instructions from the upper directions to the lower, behind-the-scenes bits and bytes binary instructions that take place in the hardware itself. The operating system can be viewed as lending services to applications and to the users of the software in order to fulfill their higher level requests.
No matter what flavor of operating system a user chooses to employ, all OS (operating systems) multitask, or perform many services and requests simultaneously. Many of the functions OS perform are in real time, and are classified as being event driven, providing instant feedback and response to the user. Many other functions and tasks are performed on a time sharing basis. These operations use CPU clock interrupts to carry out their mission.
An operating system classified as a multi-user system provides services for many users to access the hardware system at the same time. A network is a perfect example. A single workstation or hardware system not connected to a network would be a single user hardware and software operating system. One user at a time. A standalone laptop or personal computer is a good example. A system containing multiple accounts does not count as a multi-user system, as only one user may access the system by logging into their account while others must wait their turn to use the hardware system.
A distributed operating system moves closer to the multi-user description. Many independent machines are connected via a network, communicating with each other and the main server or servers, henceforth the distributed or 'multi' category.
Upon booting the system, the OS begins in supervisor mode. Necessary underlying programs and instructions load the memory and other parts of hardware, preparing the rest of the system for the upper layer instructions the user and software applications commands from the hardware. Once the entire operating system has loaded, the computer enters a protected mode, only allowing the user limited access to the resources of the machine. Some of the access is determined by the rights and restrictions allowed to the user. As software applications execute, memory is allocated as the various processes are loaded and configured to run. Between physical memory, which includes read access memory (RAM) and virtual memory (available allocated hard drive space) the operating system controls the processes and environment running smoothly. As multiple tasks are requested, the same memory space is utilized while virtual memory is paged and swapped back and forth. This would be the short lag time experienced when a memory or resource intensive application demands enough resources to perform its respective tasks.
Operating systems are also in control of application access to files and information stored on any disk or drive space location. The advancements in operating systems allow physical and virtual file access which in turn gives way to a diversity of system resources and appliances that use different application filing systems.
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