From mboxrd@z Thu Jan 1 00:00:00 1970 From: paul.winalski@gmail.com (Paul Winalski) Date: Mon, 11 Sep 2017 12:20:59 -0400 Subject: [TUHS] Happy birthday, Dennis Ritchie! In-Reply-To: References: <043e1f9205ac702c6cf01125a45d44afa956a210@webmail.yaccman.com> <9CA2C1B8-50FC-4CDB-BF3D-E922ABDE7464@cheswick.com> Message-ID: On 9/9/17, Lawrence Stewart wrote: > What, you didn’t like IBM 2741 terminals that mechanically locked the > keyboard? In the business world, these terminals were typically half-duplex and attached 4 or 8 (or more) to a control unit that communicated with the computer using bisynch protocol. It's like a telephone party line--only one terminal can communicate with the computer at a time. The remainder were locked out. [Note that Ethernet works pretty much the same way.] If you wanted to talk to the computer, you pressed the "Request" key. This caused the control unit to send an interrupt to the computer, which in due course would then unlock your terminal and talk to you. This works out OK for transaction processing, but it's not a good fit for interactive time-sharing. -Paul W.