Chuck Forsberg

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Chuck Forsberg (May 6, 1944 – September 24, 2015)[1] developed two data transmission protocols popular for uploading and downloading files from dial-up bulletin board systems in the 1990s. He received a Dvorak Award for Excellence in Telecommunications in 1992 for developing ZMODEM.[2] He was also the project engineer on the Tektronix 4010-series graphics terminals.

The widely adopted ZMODEM used a sliding window protocol. Rather than wait for positive acknowledgment after each block is sent, it sent blocks in rapid succession and resent unacknowledged blocks later. By avoiding delays due to latency, the bandwidth usable for transmission more closely approached the bandwidth of the underlying link. ZMODEM could also resume interrupted transfers without retransmitting the already-received blocks. In addition to developing the protocol, Forsberg developed software for sending and receiving files using ZMODEM.

Previously, he designed the YMODEM protocol and created its first implementation, a program called YAM.

Forsberg most recently resided in Portland, Oregon prior to his death. He ran data transmission software company Omen Technology which he founded in 1984.[3] He was an amateur radio operator (call sign WA7KGX)[4] and a licensed aircraft pilot.[3]

Jesse Walker cited Forsberg as a participant in WMAS, a pirate radio station at Western Military Academy in Alton, Illinois.[5] He graduated from the academy in 1962.


  1. ^ "Charles Alton Forsberg obituary". Retrieved 2015-10-10. 
  2. ^ John C. Dvorak. "Dvorak Awards". Archived from the original on 6 March 2014. Retrieved 8 December 2010. 
  3. ^ a b About Omen Technology at the Wayback Machine (archived September 15, 2015)
  4. ^ "Amateur License – WA7KGX – FORSBERG, CHARLES A". Retrieved 2012-02-16. 
  5. ^ Walker, Jesse (2001). Rebels on the Air: An Alternative History of Radio in America. NYU Press. pp. 199, 305. ISBN 978-0-8147-9381-7.