xcopy

MS-DOS command.

DOS' original COPY command wasn't too shiny: It could copy a file to another place, or concatenate two files, but that was just about that.

XCOPY was introduced around DOS 3 (I think, /msg me if I'm incorrect) and it gained new features later on.

It can copy whole subdirectories (switch /s), copy files with Archive attribute set (/a), files modified after certain date (/d:date), and create target directory automatically (/i). There are other switches, but their usability is limited.

In Win9x this command is actually called xcopy32, I think...

...not to mention one of the more amazing features it adopted to exploit the masses of RAM that PCs were gaining: Memory cacheing.

Regular MS-DOS copy reads one data block from the source and then writes it to the destination. Xcopy, however, reads as much stuff as it can get into conventional memory, and then writes it to the destination in a bundle. This a big deal, especially if copying from one floppy drive to another.