YB (yottabyte) - This is 2^80 bytes, or 1024 zettabytes. See also zettabyte.

Ymodem - A protocol for transferring files during direct dial-up communications. It is so named because it builds on the earlier Xmodem protocol. Ymodem sends data in 1,024-byte blocks and is consequently faster than Xmodem; however, it doesn't work well on noisy phone lines. Ymodem has undergone a few enhancements: Ymodem-Batch can send several files in one session, and Ymodem-G drops software error-correction, which speeds up the process by removing the overhead used by error-correction. This works because all modems since the V.32 era have error-correction built into the hardware.

Yottabyte (YB) - This is 2^80 bytes, or 1024 zettabytes. See also zettabyte.