Screen is a full-screen window manager that multiplexes a physical terminal
between several processes (typically interactive shells).
Each virtual terminal provides the functions of a DEC VT100 terminal and, in
addition, several control functions from the ANSI X3.64 (ISO 6429) and ISO
2022 standards (e.g. insert/delete line and support for multiple character
sets). There is a scrollback history buffer for each virtual terminal and a 
copy-and-paste mechanism that allows moving text regions between windows.

WWW: http://www.gnu.org/software/screen/