ANSI.SYS

ANSI.SYS is a device driver in the DOS family of operating systems that provides extra console functions through ANSI escape sequences. It is partially based upon a subset of the text terminal control standard proposed by the ANSI X3L2 Technical Committee on Codes and Character Sets (the "X3 Committee").

To use ANSI.SYS under DOS, a line is added to the CONFIG.SYS (or CONFIG.NT under Windows NT based versions of Windows) file that reads:

where drive: and path are the drive letter and path to the directory in which the file ANSI.SYS is found, and options can be a number of optional switches to control the behaviour. ANSI.SYS may also be loaded into upper memory via DEVICEHIGH/HIDEVICE.

Once loaded, ANSI.SYS enables code sequences to apply various text formatting features. Using this driver, programs that write to the standard output can make use of the 16 text foreground colors and 8 background colors available in VGA-compatible text mode, make text blink, change the location of the cursor on the screen, and blank the screen. It also allows for the changing of the video mode from standard 80×25 text mode to a number of different graphics modes (for example, 320×200, 640×40-column text mode) depending on which video graphics card is installed.

The standard ANSI.SYS is relatively slow as it maps escape sequences to the equivalent BIOS calls. Several companies made third-party replacements that interface directly with the video memory, in a similar way to most DOS programs that have a full-screen user interface.

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