Business Glossary

filename longer than the 11-character DOS limit. Long filenames are supported by OS/2 HPFS, Windows, Macintosh OS, and UNIX. UnderWindows 95 and later, a filename can be up to 255 characters long and can contain blanks and some special characters. Uppercase and lowercase letters are distinguished. Long filenames that contain blanks must be surrounded by quotation marks when used in commands, like this:
C:\> dir "My Program Files"
Long filenames are automatically translated into short filenames such as MY˜PRO˜1 for compatibility with DOS and Windows 3 software running under later versions ofWindows. Contrast 8.3 filename.

a multitasking, virtual memory operating system for 386 and higher PC-compatible computers. OS/2was an important predecessor ofWindows 95 (another descendant of the same IBM-Microsoft joint development project) but is now obsolete.

Like Windows, OS/2 provides multitasking, extended memory, a graphical user interface, and the ability to multitask DOS programs as well as programs written for OS/2.

OS/2 was originally developed by Microsoft in cooperation with IBM. Since version 2 it has been solely an IBM product, competing against newer versions of Windows.

an operating system, or family of operating systems, developed at Bell Laboratories in the early 1970s as a replacement for an earlier system called Multics. UNIX is noteworthy because, although developed by a small team of about four people, it is in many ways superior to operating systems developed by large teams at tremendous expense (e.g., OS/360). The most popular versions of UNIX today are Solaris and Linux. The current version of the Macintosh operating system (macosx) is based on UNIX.

The main features of UNIX include the following:

1. Highly modular, structured design. The entire system is defined in terms of a relatively small number of subroutines; UNIX can be implemented on any machine by implementing those routines. Furthermore, the operation of the whole system is based on a relatively small number of principles carried through very consistently; there is little arbitrary detail for the user to learn.
2. Extensibility. In many operating systems, users can create commands of their own that execute sequences of ordinary commands stored on files. UNIX, however, provides a full-fledged programming language for this purpose (the "shell"), with if, while, and case statements similar to those of Pascal, as well as extensive facilities for string handling.
3. Input-output redirection. Any program invoked by a command can be told to take its input from, and/or write its output onto, a file rather than the user's terminal. For example,
   sort <alpha >beta
   tells the sort program to take its input from alpha and write its output onto beta. UNIX also supports pipes, which allow one program to transmit its output directly into the input of another program. See pipe.
   Many UNIX commands, called filters, read a file and output a copy of it that has undergone some simple transformation, such as removing repeated lines. Powerful operations can be accomplished by stringing filters together through pipes.
4. Tree-structured directories. In all earlier operating systems, a user's files were kept in a single list called a directory. In UNIX, however, directories are handled like files, and a user can have an unlimited number of them, each of which must be listed in a higher directory until the main ("root") directory is reached. This makes it possible to arrange files into logical groups-for example, to put all files related to a particular project into a single directory. Tree-structured directories are a virtual necessity if one user is to keep track of more than a few dozen files.

The following are some common UNIX commands:

1. the series of characters, such as C:\TEMP> or unix%, that indicates that an operating system is ready for the user to type a command.
2. in Windows, a console modewindow in which the user can type commands (Figure 63).

simultaneous execution of two or more computer functions.

a program that extends the operating system in order to support a specific device, such as a disk or tape drive, video card, or printer.Device drivers are a very important part of Microsoft Windows. They insulate application programs from the hardware so that, for example, the manufacturer of a word processing program does not have to know what kind of printer you are going to be using, and if a new printer is invented in the future, you can use it even if it wasn't anticipated when the programwas written. Installation of device drivers usually happens automatically when hardware or software is installed; you can also add and remove device drivers from the Control Panel (see Control Panel; Plug and Play).