Operating system

Operating system (OS)
An operating system is system software that manages computer hardware and software resources and provides common services for computer users (people) and other applications that they are already installed in the computer.

For hardware functions such as input, output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from smartphones, video game consoles to web servers and all kind of computers.

Single- and multi-tasking
A single-tasking system can only run one program at a time, while a multitasking operating system allows more than one program to be running in concurrency. This is achieved by time-sharing, dividing the available processor time between multiple processes that are each interrupted repeatedly in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in preemptive and co-operative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e.g., Solaris, Linux, as well as AmigaOS support preemptive multitasking. Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multitasking. 32-bit versions of both Windows NT and Win9x, used preemptive multitasking.
 
Single- and multi-user
A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, and the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources to multiple users.
 
CUI – (Command User Interface – Single-user-system)
Note: - Single-user operating systems have no facilities to distinguish users but may allow multiple programs to run in tandem. CUI, that can be supporting to work only single user and only one function at a time in a computer and there is using only command prompts.
E.g.: - DOS – (Disk Operating System).
 
GUI – (Graphical User Interface - Multi-user-system)
Note: - A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, and the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources to multiple users.
 
The OS performs basic tasks, such as controlling and allocating memory, prioritizing the processing of instructions, controlling input and output devices, facilitating networking, and managing files. The OSs are designed for easy to work on it because the OSs have gotten facilities like pointing devices such as mouse or touch pad/screen to input the data, and these kinds of OSs have gotten “icons” viewing its own as well. Let’s say, after developed these kind of OSs, the digital world could be possible in the past and now.
E.g.: - Windows 10 OS, Linux OS, Mac OS, Unix OS, Kali Linux OS, Solaris OS and Amiga OS.