The machine ID is part of a separate mechanism that may be used to allow conditional installation of different components on different devices (e.g. in order to overcome device incompatibility etc.). The ID may be used in a condition block within the PKG file package body (or within executable code):
» Symbian OS Tools And Utilities » Installation reference » Package file format » package-body.

Note that the Machine ID and Product ID may or may not have the same numerical value on a particular device. The machine ID is guaranteed to be unique to the device, while the product ID may (contrary to its name) may be common to several devices or even absent. The mechanisms are described in greater detail in the following sections.

How does the Product ID and Platform ID dependency mechanism work?
The device contains SIS file stubs corresponding to its compatible platforms/product IDs (see z:\system\install\). When a SIS file is run, the installer compares all the product IDs from the PKG file with every SIS file stub. If any product/platform dependency listed in the .pkg file is present on the device then the application is compatible. If the application is not compatible (no matching stub) the result is passed to the UI; on Series 60 the user is warned and given the opportunity to continue installation.

UIQ phones based on Symbian OS v7.0 have a slightly different behaviour. Symbian OS v7.0 requires that only a single product ID is declared in the PKG file; if you put more than one dependency then the installation will fail. As a result a SIS file that declares compatibility with both UIQ2 and Nokia series60 binaries will install on series60 based phones, but not on UIQ2 based phones (see FAQ1232 "Can a single SIS file containing both S60 and UIQ versions of an application be Symbian Signed?" ). This will not be a limitation on Symbian OS v9 based UIQ phones.

The manufacturer that creates the phone make the decision about what product ID stubs will be present. Great efforts are made to maintain compatibility for existing functionality, so the phone will usually have Product IDs for all compatible previous platforms, the current platform, and the current device.

Notes:

• Pre-Symbian OS v9 the installer discriminates Product ID dependencies from component dependencies based on the string name ending in text "ProductID", e.g:
  (0x101F61CE), 0, 0, 0, {"SonyEricssonP9xxPlatformProductID"}
• Product and Platform IDs are the same thing - the only difference semantic; platform IDs will be present on all devices in a platform, and on future compatible devices, while product IDs tend to be (at manufacturer descretion) on the current platform.

• FAQ-1242: How many phones should I test my application on before getting it signed?
• FAQ-1232: Can a single SIS file containing both S60 and UIQ versions of an application be Symbian Signed?
• FAQ-1045: What are the Product IDs that I need to specify in my .PKG file for installation onto devices?
• FAQ-0936: How do I create an installation file working on all UIQ phones?

• FAQ-1114: Can I have a single SIS file that would install the correct version of my application depending on the device being used?