Now start with basic and very important question what is computer operating systems ? A computer operating systems (OS) are a software program that manages the hardware and software resources of a computer. The OS performs basic tasks. Those are controlling and allocating memory, prioritising the processing of instructions, controlling input and output devices, facilitating networking, and managing files.
Modern general-purpose computers, including personal computers and mainframes, have an operating system to run other programs, such as application software. Examples of computer operating systems for personal computers include Microsoft Windows, Mac OS (and Darwin), Unix, and Linux.
The lowest level of any computer operating systems is its kernel. This is the first layer of software loaded into memory when a system boots or starts up. The kernel provides access to various common core services to all other system and application programs. These services include, but are not limited to disk access, memory management, task scheduling, and access to other hardware devices.
As well as the kernel, a computer operating systems are often distributed with tools for programs to display and manage a graphical user interface (although Windows and the Macintosh have these tools built into the operating system), as well as utility programs for tasks such as managing files and configuring the operating system. They are also often distributed with application software that does not relate directly to the operating system’s core function. But which the operating system distributor finds advantageous to supply with the operating system.
The delineation between the operating system and application software is not precise. It is occasionally subject to controversy. From commercial or legal points of view, the delineation can depend on the contexts of the interests involved. For example, one of the key questions in the computer operating systems are used on most, but not all, computer systems.
The simplest computers, including the smallest embedded systems and many of the first computers did not have operating systems. Instead, they relied on the application programs to manage the minimal hardware themselves, perhaps with the aid of libraries developed for the purpose. Commercially-supplied operating systems are present on virtually all modern devices described as computers, from personal computers to mainframes, as well as mobile computers such as PDAs and mobile phones.
Command line interface (or CLI) computer operating systems can operate using only the keyboard for input. Modern OS’s use a mouse for input with a graphical user interface (GUI) sometimes implemented as a shell. The appropriate OS may depend on the hardware architecture, specifically the CPU, with only Linux and BSD running on almost any CPU. Windows NT has been ported to other CPUs, most notably the Alpha, but not many. Since the early 1990s the choice for personal computers has been largely limited to the Microsoft Windows family and the Unix-like family, of which Linux and Mac OS X are becoming the major choices. Mainframe computers and embedded systems use a variety of different operating systems, many with no direct connection to Windows or Unix, but typically more similar to Unix than Windows.
o IBM PC compatible – Microsoft Windows and smaller Unix-variants (like Linux and BSD)
o Apple Macintosh – Mac OS X, Windows, Linux and BSD
- Mainframes – A number of unique OS’s, sometimes Linux and other Unix variants.
- Embedded systems – a variety of dedicated OS’s, and limited versions of Linux or other OS’s