SideKick was an early Personal Information Manager (PIM) software application by Borland launched in 1983 under Philippe Kahn's leadership. It was notable for being a Terminate and Stay Resident (TSR) program, which enabled it to load into memory then return the computer to the DOS command prompt, allowing the user to load another application, but still activate SideKick using a hot key combination (by default: Ctrl-Alt). This approach allowed instantaneous task switching in the otherwise-single-tasking DOS operating system. Although a text mode program, its window-based interface echoed that of the Apple Macintosh, and anticipated the eventual look of Microsoft Windows 2.0. It featured a personal calendar, text editor (with WordStar-like command interface), calculator, ASCII chart, and address book/phone dialer. According to the Borland IPO prospectus, SideKick sold more than one million copies in its first three years.
SideKick 2.0 was the last DOS version.