.unix / Xenix Fax And Data Communications Software

This paper is divided into two parts: the first part mainly discusses fax software implementation under UNIX/XENIX system, the second part mainly discusses data transfer software implementation under UNIX/XENIX system.In facsimile part, we first introduced the developing process and developing direction of the facsimile technique, proposed our research subject, and then, we discussed facsimile transmission procedure in the public switch telephone network(PSTN), coding scheme for Group 3 facsimile apparatus and the implementation method of fax system based on PC. At last, we discussed design goal, design method, and implementation of fax software under UNIX/XENIX system with emphasis. Several important parts in software system, such as client program, background scheduling program, fax sending and receiving program, file format transform and coding decoding program, are described in detail.At data transfer part, we introduced simply data communication on PSTN and proposed our research subject, several popular file transfer protocols today, such as Xmodem protocol, Ymodem protocol, Kermit protocol, are analyzed. Some comparison and evaluation on their performance are done. At last, we discussed the function, design principle, and implementation of data communication software under UNIX/XENIX system.