The UNIX computer sends a job using its LPR utility. If the LPR client specifies the "l" control command, LPD leaves the job alone and assigns it the RAW data type. If the LPR client specifies the "f" command, LPD assigns it the TEXT data type and modifies the file for proper formatting. From this point on, the job is handled the same way that an MS-DOS client's job is handled.
Note that LPD depends entirely on the control command sent with the print job to tell it how to handle the job; it does not parse the rest of the job. For example, if a UNIX client sends a PostScript job and the job contains the "f" command, LPD will not recognize it as PostScript and will treat it as any other job with an "f" command.