What is the unix command for copying a file?

Internally, however, while some systems have specialized APIs for copying files (like CopyFile and CopyFileEx in Windows API), others (like Unix and MS-DOS) fall back to simply reading the contents of the old file and writing it to the new file. This makes little difference with local files, but provides an interesting situation when both the source and target files are located on a remote file server.  Operating systems with specialized file copying APIs are usually able to tell the server to perform the copying locally, without sending file contents over the network, thus greatly improving performance.  Those systems that have no comparable APIs, however, have to read the file contents over the network, and then to send them back, again over the network.  Sometimes remote file copying is performed with a specialized command, like ncopy in MS-DOS clients for Novell NetWare.