Neon-komputadór

Systems Software

Systems software consists of utilities, operating systems, compilers and interpreters. Compilers and interpreters have already been described in the programming section.

Utilities are those programs that perform very specific tasks and normally stay in the memory of a computer whilst it is in operation. For this reason they are sometimes called Memory-Resident Programs or, in the nomenclature of Microsoft, TSR's (Terminate and Stay Resident). Normally, if a computers system does not have sufficient memory to run a program it will copy data from random access memory to disk, a process called swapping. As you would imagine these are usually very important, albeit small and simple, programs. They are usually related to managing system resources such as memory management, management of processors, files and directors and interactions between different devices. An Operating System can be described as a particular set of utilities for these basic tasks.

One of the most features of an operating system is the kernel, usually responsible for handling input and output into the 'microkernel' design architecture and memory management, file systems in the larger 'microkernel' design. An example of the former include Windows NT, QNX, and Mach and of the latter, Linux, MS-DOS and Windows95. Apple's Rhapsody and MacOS X put a microkernel on top of a microkernel. The advantage of microkernels is that they're very easy to transport to other hardware. The main disadvantage is that they're not always as efficient because of their (usually) modular design. Operating Systems can be defined as follows: multiuser (multiple users can run programs simultaneously), multiprocessing (a program can run on multiple CPUs simultaneously), multitasking (more than one program can run at a time), multithreading (different parts of a program can run concurrently), and realtime (responds to input instantly).

Operating Systems are often described as the "platform", as the choice of operating system will determine what applications software can be used. The applications, as it were, "jump" from the operating system platform. Users can issue commands to an operating system through either a Command Line Interface (CLI) or through a Graphic User Interface (GUI). The former requires text-based commands to be entered at a command prompt, for example in MS-DOS: ("format a:", which would format a floppy disk drive). The latter has a variety of Windows and menus to facilitate use. The most popular operating systems for personal computers are MS-DOS, MS-Windows, MacOS and Linux. These are briefly described as follows:

MS-DOS

An acronym for Microsoft Disk Operating System and a standard operating system for PCs throughout most of the 1980s. With a CLI interface MS-DOS over the years became quite sophisticated, however at the end of the day it was limited to 16-bit application processing and did not support multiple users, multiprocessing, multitasking or multithreading. Like most general purpose operating systems, it was never intended to be real-time either. MS-DOS is the operating system behind the Windows 95 and Windows 98 user interface.

MS-Windows

MS-Windows is a number of different operating systems which are expressed collectively, including Windows 1.00 to 3.11, Windows 95 and 98, Windows ME, Windows NT, Windows 2000, and Windows XP. Earlier versions, such as Windows 3.11, Windows 95 and Windows 98, were actually Graphic User Interfaces for MS-DOS. Various versions of MS-Windows are estimated to be installed on some 90% of personal computers. Some of the key features includes virtual memory management, multi-tasking and a Graphic User Interface,

Windows 95 was a particularly significant release. Not only did it have a new user interface, it supported 32-bit applications, a significant change from MS-DOS. It also stepped beyond some of MS-DOS's endemic problems, such as being limited to 640K of main memory RAM and 8 character filenames. Windows 98 made some further changes, including the introduction of FAT32 directory structure and a user interface that integrated the Microsoft web browser (Internet Explorer) with the operating system.

Strictly speaking, there were two different source codes for Windows, one that followed the MS-DOS path (Windows 1.00 - 3.11, Windows 95, 98 and ME) and the Windows NT (New Technology) path, a complete rewrite of the Windows-DOS operating systems. Windows NT includes Windows NT versions 1,0 to 4.0, Windows 2000 (also known as Windows NT 5.0) and Windows XP (also known as Windows NT 5.1). The 'XP' is supposed to stand for 'eXPerience' (seriously!).

Windows NT (New Technology) is a 32-bit operating system that supports preemptive multitasking that uses it's own filesystem (NTFS - New Technology File System). There are actually two versions of Windows NT: Windows NT Server, designed to act as a server in networks, and Windows NT Workstation for stand-alone or client workstations. The key differences between the Windows NT-path and the Windows-95 path was the reliance of the latter on MS-DOS. WindowsNT had it's own kernel and used a NTVDM (New Technology Virtual DOS machine) to run DOS-based applications.

Windows XP is the latest incarnation of WindowsNT. Within Microsoft, WindowsXP is actually known as Windows NT 5.1. It is supposed to represent a convergence of the DOS/Windows 95 direction and the NT direction. Whilst the user interface is closer to the former, the source code is closer to the latter, meaning that the security and stability is somewhat improved to previous versions.

Linux

Linux (short 'i', lih-nucks) is a free-distributable operating system with an open source code and designed to run on a variety of hardware. With a first stable release in early 1994, Linux has developed at an amazing rate with programmers all over the world contributing freely to it's platforms. Linux started off as a hobby for student Linus Torvalds who, as a student at the University of Finland, wrote the kernel in the early 1990s. development. Whilst it currently represents a mere 2% of personal computer use many feel that it is the future operating system of choice. The People's Republic of China, for example, have recently adopted Linux as the standard all-of-government operating system.

The extraordinary thing about Linux is that noone owns it. People write programs, publish their code, have the code tested and criticized by the programming community and, if it's good enough, a distribution company (such as Red Hat or Debian) will bundle it in with a package of other programs and offer to support it. Compared to the monolithic approach to Microsoft it's pure anarchy - but many say that the open source orientation means that Linux is more stable and secure as well as providing greater options for users.

Linux is a complete multiuser and multitasking operating system with multiprocessor and mutithreading capabilities. It supports a variety of file systems, including Xenix, Unix System V, IBM's JFS, and MS-DOS/Windows95 VFAT. Applications up to 64-bit are supported. Until recently, Linux was primarily designed for servers, with excellent network and security features. More recently however it has developed a Windows-style Graphic User Interface (X-Windows) and several companies have produced applications that are very close to the MS-Office standard (such as the free, open-source, OpenOffice). If anything, the greatest problem with Linux is the sheer range of options available.

MacOS

Whilst no computers in the Ministry of Foreign Affairs and Cooperation are based on the Macintosh Operating System, or for that matter, the PowerPC processor, some brief comments about them are worthwhile. The MacOS and Macintosh computers are made by Apple Computers. First introduced in 1984 they included the revolutionary concept of a Graphic User Interface of windows, icons and a mouse for ease of use. Furthermore, because the GUI was actually part of the Operating System, the interface was similar across all applications. There can be no doubt that the Macintosh heralded a completely new way for users to interact with their computers and it is hardly surprising that many of the features have been copied to MS-Windows and the X-Windows interface for Linux. All models since 1994 are based on the PowerPC microprocessor, which uses a RISC-based architecture developed by IBM, Apple and Motorola.

In the Ministry of Foreign Affairs nearly all computers have a version of Windows installed. The older Compaq Pentium II system units usually have Windows98 installed, although some (those with extra RAM) have Windows2000 Professional. The newer Hyundai Pentium IV computers have WindowsXP installed. The Information and Communications Technology Policy Advisor uses Linux through the Red Hat 8.0 distribution on one of the older Compaq machines which technically isn't quite up to the standard required, just to show it can be done.