Hilgraeve Inc, of Monroe, Michigan, has released the Hyperprotocol data transmission protocol incorporated into its Hyperaccess/5 package for MS-DOS and OS/2 into the public domain, reports the Teleputing Hotline. Hyperprotocol combines the best features of the Z-Modem protocol with the Lempel-Ziv file compression system to give a claimed 500% data throughout improvement in the best cases – but it does of course have to be installed at both ends of the link. Z-modem is the most recent in a string of protocols that started with X-Modem. As the Hotline explains, with X-Modem, files are packeted up into 128 byte blocks and transferred block by block. Each end of the link waits for the other to give an ACK/NAK all-clear before proceeding with the next block. Y-Modem increases the block size to 1,024 bytes to save time on confirmations. With Z-Modem, data is streamed and the delay between blocks is eliminated. Data is transmitted block by block, with no perceived gap, until the receiving end asks for a pause. Z-Modem has the facility for the introduction of file compression, for file transfer resumptiom after interruption, and support for variable length blocks.
