johnston@LBL-CSAM.ARPA (Bill Johnston [csam]) (11/20/85)
Reguarding the problems of sending Tektronix 40xx Graph Mode files out over VMS serial lines .... You have run into what I consider to be a classic problem with VMS. VMS has a highly structured notion of what are files, async terminals, parallel output devices, etc.. One result of this is that the notion of record boundaries is ingrained at the lowest levels of software (the I/O device drivers) and sometimes in the devices themselves. Without rewriting the device driver for the, say DMF32 serial lines, it is not possible to get more than 511 (if I recall, though some devices go to 65K) bytes out with out a line feed being inserted by the device driver. (UNIX does not have this problem because of its pleasantly simple minded view of files and devices; and no, I will not be drawn into any religious discussions. Both systems have their merits and faults.) The QMS Graph Mode emulation changes from graphics mode to alpha mode upon receipt of an LF, hence the loss of vectors and printing of characters. Further, in order to correctly insert LF's in the Graph Mode code you have to run a software state machine emulating a Tektronix terminal (at least for instruction cracking) to locate legal places to insert LF's, which may have to be followed with a GS, depending on the state. We nearly rejected three Talaris 2400 printers because of this problem. I believe that the ultimate resolution of this problem was that Talaris provided the above mentioned software, which after cracking the Graph Mode code, output QUIC code which is much more 'unit record' oriented. More information may be gotten from Marty Gelbaum (M_Gelbaum@lbl.arpa). I don't know if this code can be distributed, the original version came (I think) from QMS but was unacceptable for efficiency reasons. The current version is supplied by Talaris.(You could ask Cal Burghart at Talaris, 619-587-0787.) Another source of code is Van Jacobson (VLJacobson@lbl.arpa), who has written a LEX program to crack Tektronix Graph Mode code. Once cracked its is easy to modify by, for instance, the addition of correctly placed LF's and GS's. Sorry if this duplicates other messages, I am far behind in reading this list. Bill Johnston (WEJohnston@lbl.arpa)