Symbian Example

Symbian operating system and Nokia's S60 based on Symbian are well known for breaking the binary compatibility here and there, changing constants and interfaces between the minor versions, etc. As Mika Raento puts it it "Nokia is completely schizophrenic when it comes to backward compatibility". Some interfaces are maintained with the help of various compatibility layers for a long time, while another interfaces sometimes are dropped or heavily re-engineered even within the same S60 version.

While it is definitely up to Nokia and Symbian when and how to change their interfaces, the big problem for the external developers in that the principles for maintaining or dropping the backwards compatibility are not known. Therefore the software vendors don't know on which APIs to rely and of which not to rely.

One way of solving this is to get a compatibility principle based on the business value of maintaining the compatibility, i.e. on how many useful applications rely on this or that particular API. The rumors tell that when Microsoft released its Windows 95 it invested huge amount of efforts into making the OS work even with particular popular games that contained bugs normally incompatible even with the DOS (where the games worked by accident).

I first heard about this from one of the developers of the hit game SimCity, who told me that there was a critical bug in his application: it used memory right after freeing it, a major no-no that happened to work OK on DOS but would not work under Windows where memory that is freed is likely to be snatched up by another running application right away. The testers on the Windows team were going through various popular applications, testing them to make sure they worked OK, but SimCity kept crashing. They reported this to the Windows developers, who disassembled SimCity, stepped through it in a debugger, found the bug, and added special code that checked if SimCity was running, and if it did, ran the memory allocator in a special mode in which you could still use memory after freeing it.

As we know in the end this attitude made Windows the dominant desktop OS on the Earth.

In the Symbian world the situation is that opposite that despite the growing Symbian market share, Nokia's own bloggers notice that during the last couple of years the third party fail to cope with the changes and the usefulness of the 3rd party apps is diminishing. Is it because the Nokia applications improved by the order of magnitude? - I doubt. Why doesn't Nokia go over the popular applications third party providers and S60 licensees and ask them what APIs they rely on? Then Nokia could make a list of APIs guaranteed to be maintained for a long time (e.g. two years), for medium time (e.g. one year) and for undefined amount of time. Preferably with the tests attached.

Certainly, at the moment being almost the market monopoly Nokia might not have a solid business reason for it. Just the same way as Palm did not have it until Windows Mobile with the hordes of loyal developers destroyed the Palm business in just a few years.