Unit 1. Operating systems

I. Read the following words:

vary, capability, require, process, supervise, error, occur, batch, overlap, queue, sufficient, sophisticated, resources, frequently, transaction, currently, control, layer, command, reliable, achieve, supercomputer, remote, installation, organization, initial, access, proprietary, coherent, fairly, partly, virtue, towards, directly, raw, transfer, version, support.

II. Before you read the text try to answer the following questions:

1. What is an operating system?

2. What is the main function of an operating system?

3. What operating systems do you know?

III. Read and translate the following text. Operating systems

Computers vary considerably in size, capability and type of application. There is a wide variety of ways in which they can be operated. Each type of computer operation requires a different type of operating system. Most microcomputers and some minicomputers can only process one program at a time. This is a single program operation and it requires only a simple operating system. The operating system supervises the loading and running of each program and the input and output of data. Any errors occurring are reported.

Next in complexity is batch processing. A number of programs are batched together and then run as a group. Although, the programs are actually run one at a time, input and output from various programs can overlap to some extent. Programs are normally queued up for batch processing and the operating system starts the next program in the queue as soon as sufficient computing resources are available for it.

Similar to batch processing, but much more sophisticated, is multiprogramming. At any time, a number of programs are on the computer at various stages of completion. Resources are allocated to programs according to the requirements of the programs and in order to maximize the usage of the different resources of the computer. A particular type of multiprogramming is transaction processing designed for systems which must run large number of small programs very frequently.

Like the question «What is a computer?» the question «What is an operating system?» can be answered at several levels. Firstly, an operating system is a program, or set of programs. Operating systems vary in size from very small to very large, but all are pieces of software. In the past, almost all operating systems were written in a low level language. Currently, many operating systems are partly or completely written in high level languages. Secondly, an operating system is, by virtue of its name, a system. It is a collection of parts, working together towards some common goals. Thirdly, a computer may be regarded as a set of devices or resources, which provide a number of services, such as input, processing, storage and output. The operating system of the computer may be regarded as the manager of these resources. It controls the way in which these resources are put to work. Finally, an operating system is the lowest layer of software on a computer. It acts directly on the «raw» hardware of the computer. It supports other layers of software such as compilers and applications programs. The part of the task of an operating system is to avoid users from the complexities of direct use of the computer hardware. In summary, an OS is a program or set of programs, driving the raw hardware of a computer, which manages the resources of the computer in accordance with the certain objectives.

Mac OS X is a line of proprietary, graphical operating systems developed, marketed and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac OS X is a UNIX operating system built on the technology that was developed at NeXT during the second half of the 1980s and up until Apple purchased the company in 1997. The operating system was first released in 1999 as Mac OS X Server 1.0. Since then, four more distinct end-user and server editions of Mac OS X have been released. On 26 October, 2007, Apple released Mac OS X 10.5, nicknamed «Leopard». The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart but usually runs on Macintosh server hardware. Mac OS X Server includes workgroup management and administration software tools that provide simplified access to key network services, including a mail transfer agent and domain name server.

Microsoft Windows family of operating systems originated as a graphical layer on the top of the older MS-DOS environment for the IBM PC. Modern versions are based on the newer Windows NT core that was originally intended for OS/2 and borrowed from VMS. Windows runs on 32-bit and 64-bit Intel and AMD processors but earlier versions also ran on the DEC Alpha, MIPS and PowerPC architectures. Windows is also used on servers supporting applications, such as web and database servers. The most widely used version of the Microsoft Windows family is Windows XP, released on 25 October, 2001. In November 2006, after more than five years of developing, Microsoft released Windows Vista. It was new version of Microsoft Windows which contained a large number of architectural changes and new features (user interface and visual style Windows Aero, security features and multimedia applications, such as Windows DVD Maker). The newest operating system from Windows family is Windows 7.

Unix-like family is a diverse group of operating systems with several major sub-categories including System V, BSD and Linux. The name «Unix» is a trademark of The Open Group. «Unix-like» is commonly used to refer to the large set of operating systems which resemble the original Unix. Unix systems run on a wide variety of machine architectures. They are used as server systems in business, as well as workstations in academic and engineering environments. Free software Unix variants, Linux and BSD, are popular in these areas. The market share for Linux is divided among many different distributions. Historically, users installed a distribution by themselves, but in 2007 Dell began to offer the Ubuntu Linux distribution on home PCs. Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on the vendor's hardware. Others, such as Solaris, can run on multiple types of hardware, including servers and PCs.

Linux is a generic term that commonly refers to Unix-like computer operating systems that use Linux kernel. This is one of the most prominent examples of free software and open source development. The name «Linux» comes from the Linux kernel, originally written in 1991 by Linus Torvalds. The system's utilities and libraries usually come with the GNU operating system, announced in 1983 by Richard Stallman. Linux can be controlled by one or more text-based command line interfaces (CLIs), graphical user interface (GUI), or through controls on the device itself. On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces, though a variety of other user interfaces exist. The primary difference between Linux and other popular operating systems is that the Linux kernel is free and open source. Historically, Linux has mainly been used as a server operating system and has risen to prominence in that area. In September 2006, Netcraft reported that eight of the ten most reliable Internet hosting companies ran Linux on their web servers. Linux is the cornerstone of the LAMP server-software combination (Linux, Apache, MySQL, Perl/PHP/Python) which has achieved popularity among developers and is one of the most common platforms for website hosting. Linux is commonly used as an operating system for supercomputers. In August 2008, out of the top 500 systems, 423 ran Linux. A Linux distribution, commonly called a «distro», is a project that manages a remote collection of Linux-based software and facilitates installation of the Linux operating system. Distributions are maintained by individuals, volunteer organizations and commercial entities. They include system software and applications software in the form of packages and distribution-specific software for initial system installation and configuration as well as later package upgrades and installs. A distribution is responsible for the default configuration of the installed Linux system, system security and integration of the different software packages into a coherent whole.