21. The original XMODEM used a 128-byte data packet, the basic block size used on CP / M floppy disks. 22. Again, a normal XMODEM implementation would simply discard the packet, the assumption being that the packet number had been corrupted. 23. The design also included terminal emulation and XMODEM file transfer software which enabled the NC100 to communicate through dial-up analogue modems. 24. XMODEM became extremely popular in the early bulletin board system ( BBS ) market, largely because it was so simple to implement.25. This included the file's name, size, and timestamp, which were placed in a regular 128 byte XMODEM block. 26. The original YMODEM was essentially the same as XMODEM except that it sent the file's padding at the end of the file. 27. In the case of XModem , for instance, that means it takes of a second for the cycle to complete for a single packet. 28. Thus, for example, the XMODEM -CRC extension, an early use of CRCs in software, uses an msbit-first CRC. 29. These archive files were then compressed with ZIP and forwarded to ( or polled by ) another nearby node or hub via a dialup Xmodem session. 30. Whereas a normal XMODEM transfer would start with the sender sending " block 1 ", the TeLink header packet was labeled " block 0 ".
