ANSI.SYS

Summary

ANSI.SYS is a device driver in the DOS family of operating systems that allows a program to control the display by inserting ANSI escape sequences into its output. Without this a program could only add lines of text to the bottom of the screen, unless it directly manipulated the graphics hardware. Using ANSI.SYS would have allowed graphics device independence in IBM clones; but it was not installed by default and was notoriously slow.