ANSI Standard X3.64: A set of extensions to the popular ASCII encoding standard. It uses a Control Sequence Introducer (CSI -- usually defined as 'Esc-[') to define a set of control sequences for text mode display devices. These control sequences can change text colors, sizes, and position the cursor on the screen, among other things. The international equivalent of X3.64 is ISO standard DP6429.

This standard is often referred to as simply 'ANSI' in the context of text mode display and terminal drivers. Non-standard, extended versions of X3.64 exist for text based systems as well. They are usually referred to as FANSI to distinguish them from plain ANSI drivers.