RP: Read a Procedure from Disk

RP will read a maximum of 2500 lines, with a maximum of 80 characters per line, from the designated filename into the procedure buffer. Unless otherwise specified in 'filename', RP will read from the default directory for procedures, which may be displayed by the command PRINT DIR, and uses the default extension. As an example, suppose the default procedure is /vista/procedure and the default extension is .pro