backup creates a disk copy of the file with suffix suffixed to the name. backup also backs up backed up copies of this file to a level of 4. Backed up copies are hidden by prefixing a '.' to the name Default suffix -s '=' if third parameter, p, is negative, primary copy is not kept. Dates & permissions are preserved. backupm makes backup of multiple file using default parameters unback reverses the action og backup, with default parameters, if primary file does not exist or the -f parameter is set