From multiprogramming to timesharing

Multiprogramming boosted the efficiency of computers, yet it was timesharing that improved the user experience.

Multiprogramming allowed multiple programs to run at the same time. Prior to multiprogramming, a computer could run one and only one program at a time. (Very similar to PC-DOS.) But multiprogramming was focussed on CPU utilitization and not on user experience.

To be fair, there was little in the was of "user experience". Users typed their programs on punch cards, placed the deck in a drawer, and waited for the system operator to transfer the deck to the card reader for execution. The results would be delivered in the form of a printout, and users often had to wait hours for the report.

Timesharing was a big boost for the user experience. It built on multiprogramming, running multiple programs at the same time. Yet it also changed the paradigm. Multiprogramming let a program run until an input-output operation, and then switched control to another program while the first waited for its I/O operation to complete. It was an elegant way of keeping the CPU busy, and therefore improving utilization rates.

With timesharing, users interacted with the computer in real time. Instead of punch cards and printouts, they typed on terminals and got their responses on those same terminals. That change required a more sophisticated approach to the sharing of resources. It wouldn't do to allow a single program to monopolize the CPU for minutes (or even a single minute) which could occur with multiprogramming. Instead, the operating system had to frequently yank control from one program and give it to another, allowing each program to run a little bit in each "time slice".

Multiprogramming focussed inwards, on the efficiency of the system. Timesharing focussed outwards, on the user experience.

In the PC world, Microsoft focussed on the user experience with early versions of Windows. Windows 1.0, Windows 2, Windows 3.0, and Windows 95 all made great strides in the user experience. But other versions of Windows focussed not on the user experience but on the internals: security, user accounts, group policies, and centralized control. Windows NT, Windows 2000, Windows XP all contained enhancements for the enterprise but not for the individual user.

Apple has maintained focus on the user, improving (or at least changing) the user experience with each release of Mac OSX. This is what makes Apple successful in the consumer market.

Microsoft focussed on the enterprise -- and has had success with enterprises. But enterprises don't want cutting-edge user interfaces, or GUi changes (improvements or otherwise) every 18 months. They want stability. Which is why Microsoft has maintained its dominance in the enterprise market.

Yet nothing is constant. Apple is looking to make inroads into the enterprise market. Microsoft wants to get into the consumer market. Google is looking to expand into both markets. All are making changes to the user interface and to the internals.

What we lose in this tussle for dominance is stability. Be prepared for changes to the user interface, to update mechanisms, and to the basic technology.