11/3/71                                             /DEV/PPT (IV)

NAME            ppt  --  punched paper tape

SYNOPSIS        --

DESCRIPTION     ppt refers to the paper tape reader or punch, de-

                pending on whether it is read or written.

                When ppt is opened for writing, a 100-character

                leader is punched.  Thereafter each byte written

                is punched on the tape.  No editing of the char-

                acters is performed.  When the file is closed, a

                100-character trailer is punched.

                When ppt is opened for reading, the process waits

                until tape is placed in the reader and the reader

                is on-line.  Then requests to read cause the

                characters read to be passed back to the program,

                again without any editing.  This means that sev-

                eral null characters will usually appear at the

                beginning of the file.  Likewise several nulls

                are likely to appear at the end.  End-of-file is

                generated when the tape runs out.

                Seek calls for this file are meaningless and are

                effectively ignored (however, the read/write

                pointers are maintained and an arbitrary sequence

                of reads or writes intermixed with seeks will

                give apparently correct results when checked with


FILES           --

SEE ALSO        lbppt, dbppt, bppt format


BUGS            Previously, there were separate special files for

                ASCII tape (which caused null characters to be

                suppressed) and binary tape (which used a blocked

                format with checksums).  These notions were con-

                ceptually quite attractive, but they were dis-

                carded to save space in the system.

OWNER           ken, dmr