Printer-friendly version
Glossary for the entire site, across all courses and subjects.

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O
P | Q | R | S | T | U | V | W | X | Y | Z | ALL


Also known as: Ymodem Y-Modem is an error-correction protocol used in the transfer of serial data files between modems. Y-Modem is based on the earlier X-Modem protocol, but has the additional feature of being able to cope with a batch transmission mode, in which a number of files can be sent with one command. For greater efficiency Y-Modem can also handle data with a variable block size of up to a maximum 1024 bytes (1 kB). During transmission, the size of text and binary files is included in the Y-Modem header, so that the exact file length will be retained after transfer. The error detection method in Y-Modem is cyclic redundancy check (CRC). A later version of Y-Modem, Y-Modem-G, transmits data in a continuous stream and does not acknowledge the blocks successfully received; it is only the blocks with detected errors that cause a negative acknowledgement (NAK), thus prompting the resending of data