Fog Creek Software
Discussion Board

Backwards Compatability

I that latest article, Joel made mention of Backwards Compatability. That, to me, seems to be a a thread common to the  giants.

When IBM got into the business, the technology of the day was punched cards, and mechanical sorting/adding machines that used those cards. Rather than forcing their potential clients into new technology (like UNIVAC was trying to do with magnetic tape, etc.) IBM used a punched card reader on their computer (IIRC slower and more expensive than the UNIVAC model).

This meant that their potential customers could keep everything they had (process and all), and just add the computer as a way to augment what they already had. Eventually the computer took over more and more of the process, and the new data entry methods were allowed to phase in oer time.

The same thing seemed to happen with the PC. Of all the machines that came out in the late 70's and early 80's, it seems to me that the PC was the one that allowed for the smoothest transition (i.e., using off the shelf, non-proprietary hardware, etc.). Additionally, as the OS evolved, you could still run your old programs (how long ago was it that the Windows line stopped being able to run Wordstar 1.0)

The exception to the rule of course being Oracle, which will drag you kicking and screeming to the next version of the database, and make thier development tools not paticularily backward compatible. But when they have you by the b*lls (follow or you'll lose support), what can you do?

Sean Ennis
Wednesday, June 16, 2004

It is a paradox.

The 1965 IBM 360 OS (whose development led to the Frederick Brooks "Mythical Man-Month" book) proved very popular as well -- so popular, even IBM 3090's made in the 1990's supported an 'emulation mode' to run 360 programs.  My point being that the 'backwards compatibility' of WinXP to MSDOS programs did not originate with Windows.

There is a definite incentive for OS vendors to provide backward compatibility.  Even though this 'sets in concrete' various limitations of the earlier OS, it dramatically reduces the cost of ownership -- and the cost of upgrading to the new OS.

Wednesday, June 16, 2004

*  Recent Topics

*  Fog Creek Home