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The focus of this guide is on the operating system, a form of system software that acts as the intermediary between the computer user, the computer hardware, and the computer software.

As such, the operating system (OS) is the most important piece of software on the computer. It manages all of the computer's resources, including its memory, CPU, and storage capacity, as well as data, applications, and utility programs.

Over the years, thousands of operating systems have been written, although most of them are no longer in use.

In the early days of computers, operating systems were written to power a single computer, often accommodating one user and one task at a time. Without access to a network, these operating systems managed a single CPU, executing one process at a time. Monitors and peripheral devices were connected by cable.

Network operating systems and distributed operating systems allowed for the access of multiple processes and devices, even allowing users in remote places to perform multiple tasks.

A real-time operating system is one that operates in an environment with urgent, time-critical requirements, such as those developed to fly jet aircraft.

Embedded operating systems power computers that are housed within other products, such as automobiles, medical devices, and handheld games. Traditional operating systems are often too large and likely to make impossible demands on these devices, which generally have little memory and internal storage capacity.

Most of us are concerned with standard computer operating systems, such as those that power our computers, laptops, tablets, and smartphones.

Once computers began to be mass-produced, operating system software became standardized and shipped with each computer product line, such as those powering the computers and mobile devices produced by Microsoft and Apple, as well as an array of Unix/Linux-type operating systems, Solaris, Novell, and some others.

As the chief piece of software in a computer, the OS has responsibility for all of the computer system's hardware and software. To function properly, it needs to boot up successfully.

When the computer is first turned on, it runs a sequence of instructions known as a boot sequence, which is burned onto a chip. Known as firmware, these instructions dictate the proper sequence necessary for getting the computer running. This startup sequence often includes self-tests to ensure that the computer's hardware is functioning properly, loading device drivers, and initializing specific sequential tasks, allowing the boot process to proceed. This process is usually accomplished without input from the user, but it is both complex and critical.

Once the bootup process has completed, the OS is responsible for dealing with requests for access to each CPU, deciding which requests should be honored first, and so on. It also tracks the progress of each process once it begins running

Although each operating system accomplishes similar tasks, they do not necessarily do so in the same way. Although many of the differences are hidden to the user, others are stark.

My first computer was a Coleco Adam in the early 1980s, and it was followed by a Tandy 1000-SX. The Coleco Adam used a CP/M operating system, while the Tandy was powered by a version of DOS, which was similar to my next several computers, which ran on MS-DOS. However, I have also used OS/2 and every version of Windows from 1-10. Although I have primarily used a Mac since 2008, I have had a few computers powered by various Linux distributions, including a Raspberry Pi.

Although Microsoft Windows dominates the market, there are several versions of the Windows operating system still in use. The Windows OS began as a graphical implementation of MS-DOS, although few Windows users have reason to drop to terminal mode any longer.

The next most popular OS is the macOS used by Apple desktop systems, with iOS being the operating system for Apple's mobile devices. Although the classic Mac OS, which had been the primary Apple OS since 1984, was developed by Apple for Apple systems, its current macOS is a UNIX operating system built on technology that had been developed at NeXT from the mid-1980s until Apple purchased the company in 1997. Thus the current OS powering Macintosh and MacBook computers is a Unix-type OS.

The Unix-like family of operating systems has spawned several variants, such as BSD (FreeBSD, NetBSD, and OpenBSD) and several Linux distributions, the most popular of which are Debian, Fedora, and Ubuntu, as well as commercial Linux distributions like Red Hat Enterprise Linux.

The focus of this category is on computer operating systems, popular or unusual. These may include the operating systems powering desktop and laptop computers, as well as those powering tablet devices and smartphones.







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