DOS

DOS

DOS (Disk Operating System) was developed by IBM and Microsoft and was the first operating system used by IBM microcomputers.

For years, DOS remained the unchallenged standard for operating systems used by IBM PCs and IBM-compatible machines.

Most seasoned microcomputer users are comfortable and familiar with DOS.

DOS uses a command-driven interface, where you are required to key in command lines to tell the operating system to perform operations.

Filenames Under DOS

Under DOS, a file’s name has two parts. The first part, called the filename, contains up to eight characters. The second part, called the file extension, contains up to three characters.

When you write the file extension in DOS commands, you separate the extension from the filename with a period. Acceptable file extensions for program files are .com, .bat, and .exe. For example, the WordPerfect program file is named WP.exe. Its filename is WP and its file extension is .exe.

With the introduction of Windows 95, long filenames traditionally used only by the Macintosh operating system became available to IBM-compatible PCs. Under Windows 95 and later Windows generations, filenames can be as long as 255 characters and may contain spaces.

You must be careful when using long filenames with Windows 9x because Windows 9x still contains a portion of DOS, which can only understand an 8-character filename, 3-character extension format. When the DOS part of the system is operating, it will truncate long filenames and assign new 8-character ones.

Memory Addressing Under DOS

In DOS, memory is divided into different areas. This division of memory began with DOS and later was used by Windows 3.x and Windows 9x. The first versions of DOS could only access the first megabyte of memory (0 to 1024K) addresses. Later, DOS extenders were included with the operating system so that memory above 1024K could be accessed.