{"id":1154,"date":"2023-04-19T14:42:54","date_gmt":"2023-04-19T21:42:54","guid":{"rendered":"https:\/\/mcjones.org\/dustydecks\/?p=1154"},"modified":"2025-12-15T20:02:00","modified_gmt":"2025-12-16T04:02:00","slug":"cal-timesharing-system-before-computers-were-personal","status":"publish","type":"post","link":"https:\/\/mcjones.org\/dustydecks\/archives\/2023\/04\/19\/1154\/","title":{"rendered":"CAL Timesharing System: Before computers were personal"},"content":{"rendered":"\n

In 2023 computers are all around us: our phones, tablets, laptops, and desktops, and lurking inside our television sets, appliances, automobiles, to say nothing of our workplaces and the internet. It wasn\u2019t always that way: I was born in 1949, just as the first stored-program digital computers were going into operation. Those computers were big, filling a room, and difficult to use. Initially a user would sign up for a block of time to test and run a program that had been written and punched into paper tape or 80-column cards.cThe fact that an expensive computer sat idle while the user was thinking or mounting tapes seemed wasteful, so people designed batch operating systems that would run programs one after the other, with a trained operator mounting tapes just before they were needed. The users submitted their card decks and waited in their offices until their programs had run and the listings had been printed. While this was more efficient, there was a demand for computers that operated in \u201creal time\u201d, interacting with people and other equipment. MIT’s Whirlwind<\/a>, TX-0<\/a>, and TX-2<\/a> and Wes Clark’s LINC<\/a> are examples.<\/p>\n\n\n\n

The ability to interact directly with a computer via a terminal (especially when a display was available) was compelling, and computers were becoming much faster, which led to the idea of timesharing: making the computer divide its attention among a set of users, each with a terminal. Ideally the computer would have enough memory and speed so each user would get good service. Early timesharing projects included CTSS<\/a> at MIT, DTSS<\/a> at Dartmouth, and Project Genie<\/a> at Berkeley. By 1966, Berkeley (that is, the University of California at Berkeley) decided to replace its IBM batch system with a larger computer that would provide interactive (time-shared) service as well as batch computing. None of the large commercial computers came with a timesharing system, so Berkeley decided they would build their own. The story of that project\u2014from conception, through funding, design, implementation, (brief) usage, to termination\u2014is told here:<\/p>\n\n\n\n