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Operating System

The software that "runs" a computer. It keeps track of and lets users modify, move copy and delete files. It handles devices such as printers, sound cards and mice. Without the operating system the computer could not run applications, such as Libre Office or Garage Band. Examples of operating systems include MS DOS, Apple iOS, Mac OS Sierra and all flavors of Windows.


An operating system that attempts to be nearly identical in function to the much older Unix system. Originally designed by a Finnish computer science student in his spare time in 1991, Linux grew rapidly in popularity and power.


A piece of hardware with a screen and keyboard that enabled users to connect to and interact with mainframe and minicomputers. Terminals were commonly used before personal computers to enable multiple users to share the resources of a large and expensive computing center. Rows upon rows of terminals were located in accounting offices, law firms and college student computer labs. They were either connected via phone cables via a local area network to the host computer, or they were connected via telephone lines, using modems. Sometimes they were connected by leased lines from the phone company or serial ports which cabled the terminals directly to an interface board on the host computer. In the early days of the internet, the host computers became linked to each other via the fledgling internet, and terminals still connected the users to their respective host computers.

Terminal Emulator

Software that runs on a personal computer that mimics the functions of a terminal. Terminal emulators run under all operating systems and effectively turn the personal computer in to a terminal for connecting to a "host" computer. Today, users typically run terminal emulators to connect to another computer via the internet, though sometimes terminal emulation is used to connect to another machine, typically running Linux on the company's local area network.

Virtual Machine

Software that mimics the function of a computer, but which runs on an operating system. A Mac running a Windows virtual machine is still running the Mac operating system, but Windows thinks it is running on a real PC, rather than on a "virtual" PC, a computer created entirely out of software. Virtual machines can be saved, so it's easy to back up their hard disks before making changes that potentially effect their stability. They make good platforms for testing new software, running programs that might infect a system with viruses, or running one version of Windows on another version. For example, you can run Windows 2000 under Windows 7. For another example, you can set up Firefox in a virtual machine and browse to sites that might infect your computer because the only machine they'll infect is the virtual one, which can simply be erased when you are finished. Or you can simply open the clean backup you made prior to the virtual machine becoming infected.

Vmware and Virtualbox

Two software packages that both do the same thing: let users create virtual machines. Multiple virtual machines can co-exist on the same single computer.

Serial port

Sometimes called a communications port, this was often the only method of connecting one computer to another. Modems, for sending data over telephone lines, were typically connected to serial ports. Today USB ports have largely replaced their function, but operating systems still are aware of, and can communicate with these physical ports. The Braille 'N' Speak is an early blindness notetaker with a serial port. Most hardware speech synthesizers also are cabled via serial ports. On the PC, ports are named Com1, Com2, Com3 and so on. On Linux, they are named ttyS0, ttyS1, ttyS2, ttyS3 and so on. So Com1 corresponds to ttyS0 and Com4 corresponds to ttyS3.

Virtual Serial Port

Software that makes the operating system under which it runs believe a real, physical hardware port is attached to the machine. These are used to test software that expects to find a real serial port, or to get virtual machines to connect to a terminal emulator. A computer can be running multiple virtual serial ports and still it can have physical serial ports as well, and as long as each of these ports gets assigned a different device name, there is no conflict.


The first widely used protocol for connecting computers on the internet to each other interactively and in realtime. In a telnet session, you supply a username and password, and then connect to the remote computer over the internet. Telnet is still used commonly to connect to some routers.


A modern connection protocol which for ordinary users, works just like telnet because they supply a username and password to log in. However ssh is far more complex for the advanced user or system administrator, and allows sessions to be encrypted. Ssh is much more secure than telnet and is recommended for most connections where data needs to be kept private.

Command line

An interface that uses text only and no menus to control software. Users type in commands with parameters to tell the running program what to do. For example, in a graphical environment, to open a file, a user might locate the file menu and choose open. In a command-line environment, the user might type in the program's name, followed by a space, followed by the -F parameter, followed by a space and the name of the file to open. Though harder to learn, a command line interface is superior to a graphical environment in many situations. It can be scripted, which means programs can be written to control the behavior of software. If you wanted certain reports printed every day at 3:30 PM, doing this with a command line would be easier to automate. It is also helpful to have a command line interface when supporting users, because you can direct them to type in exact commands instead of wondering if they've clicked on the right icon. Lastly, a command-line interface lets you accomplish a great deal with minimal bandwidth so it works well over slow connections, with older hardware or when resources, like memory is limited. Multiple users working in command-line environments can be productive on a machine that is too slow to even support a single user in a more memory and processor-intensive graphical environment.


The default Linux interface, which is text-based. Graphical user interfaces require more resources, hence console interfaces are not exclusively for blind users. At the console, a machine can be accessed remotely, via a terminal, or directly, with a keyboard and monitor attached directly to the machine running Linux.

Archiving and Zip

The term archive is often used to identify a group of files that have been bundled together in to a single file to make them easier to download or back up. The process of bundling lots of files in to one large file is often called zipping, but over the years, a variety of compression schemes have been used to both bundle the files together and reduce the archive's overall size. Linux uses compress, tar and gunzip, Windows uses zip and seven-zip. MS-DOS used the .arc format, lzh, lbr and sqz. Macs use another compression scheme. Unzipping or extracting is the process of rebuilding the individual files, usually by copying them out of the archive and in to their own individual directory. Some programs that compress and uncompress are commercial and some are open-source.

Host computer

The computer that is running a session. If you connect to another computer with yours, the computer you connect to is the host. If you are running a virtual machine, the actual hardware machine running the virtualization software is the host.

Guest operating System

Usually refers to an operating system running under a virtualization package. If Virtualbox is running on Linux and inside, it is running Windows 98 in its virtual machine, then Windows98 is the guest.


In Linux, this is the program that runs in the background that lets users control Linux. Also called a command interpreter, there are a variety of shells users can choose. One, however is always running by default and that is usually bash.


The Bourne Again SHell, Bash attempted to take all the good features of the command interpreters that came before and meld them in to one program. Bash is powerful and easier to use than the shells that came before. It is the default on most Linux systems.


The Grand Unified Boot Loader: this was written to solve problems users had booting multiple operating systems on one PC. People for example, wanted Windows and Linux to co-exist, so there needed to be a reliable method for booting one or the other, without them interfering with each other's space on the hard drive. People also wanted to be able to keep different Linux kernels on their hard disks and boot individual ones at various times. Many other boot managers exist, and grub is now at version 2, and is by far the most popular in the Linux community. Grub displays a prompt and a menu before the main operating system starts. Grub's output can be redirected to a serial port so that even a sighted user could work on a machine without the need for a keyboard and monitor attached.


The operating system code which controls devices and hardware. The Linux kernel has been through a multitude of changes and is developed by a worldwide community of mostly volunteer users. The kernel can be readily recompiled so that advanced users can include drivers they need or eliminate drivers for hardware they do not have.

Distribution (Distro)

A "flavor" of Linux frequently assembled by volunteers. Distro is simply a shortened form of the term. Redhat is an example of a commercial distribution. Vinux is a distro for vision impaired and blind users. Distros have been designed for education, gamers, the health care industry or people who love to do video editing. There are distros for people with old, slow hardware and distros for people with modern speedy systems who enjoy tweaking them for the best performance. Ubuntu is a very popular distro. It is based on the Debian distribution, famous for its stability, ethics and conservative release cycle. Grml, another distro based on Debian is designed to boot from a CD or USB stick, run live and support system administrators. Grml is popular with blind users because speakup with espeak is included.


A screen reader for the graphical user interface on Linux. Orca has support for Braille, and speech. It is not as mature as typical Windows screen readers, does not make all graphical interfaces accessible and requires more system resources than Speakup.


A screen reader for the console (text-based command-line) interface to Linux. Speakup is built in to the linux kernel. It is optionally included with some distros, and can be added to any distro by an advanced user. Though it is not necessary to have speakup to access a linux machine, it gives the best access for advanced users, because they can read the screen throughout the entire boot-up and shut-down process. Originally, Speakup was designed to only support a limited selection of hardware speech synthesizers. Various add-ons have enabled it to support software speech as well. Note that Speakup does not work in any graphical user interface.


A software speech synthesizer that is popular with the blind community because it is small, fast and portable. It is also the default synthesizer for the Windows screen reader, NVDA which uses the Max varient.


A small program (technically known as a connector) that enables Espeak to be used as software speech for Speakup.


On the Mac, Windows, DOS and Linux, directories are the same thing: a place on the hard disk with a name where a similar group of files can be saved. Usually a directory itself is a file, though users typically just see its name. A directory called Reports, and a directory called Paystubs, keep these items separate. Because the Mac and Windows graphical environments both display directories with folder icons, users commonly also refer to directories as folders, though the terms are synonomous.

Parent Directory

The directory that holds your current directory. If you are working with Letters under Documents, then Documents is your parent directory.


A part of the hard disk that is physically reserved for a specific purpose. Though all operating systems today use partitions, Linux is flexible, enabling you to set up separate partitions for user and system data, for backups, for installing especially large software packages and for separating out files which are necessary to boot the machines. Beginners can install Linux without needing a detailed knowledge of partitions. Partitioning also allows a system to "dual-boot" between Windows and Linux, enabling both operating systems to co-exist on the same hard disk.


A website that stores a copy of another site. A mirror in the United States might keep a copy of data originally on an Australian site so that people living in North America can get a faster download of the data and save the Australian's site the added cost of extra bandwidth usage .

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Page last modified on May 25, 2020, at 10:16 PM