Debian-Installer is the installation program for Debian. It was originally written for the Debian 3.1 release (codename: “sarge”), although the first "release" version of a Linux distribution it was used with was Skolelinux Venus (1.0). It is also one of two official installers available for Ubuntu; the other being called Ubiquity (itself based on parts of debian-installer) which was introduced in Ubuntu 6.06 (codename: "Dapper Drake").
It makes use of cdebconf (a reimplementation of debconf in C) to perform configuration at install time.
Originally, it only supported text-mode and ncurses. A graphical front-end (using GTK+-DirectFB) was first introduced in Debian 4.0 (codename: “etch”). Since Debian 6.0 (codename: “Squeeze”), it uses Xorg instead of DirectFB.