Developers working on applications for 64-bit Windows will find the development environment virtually identical to the development environment for 32-bit Windows. The existing APIs have been modified where necessary to allow them to reflect the precision of the platform on which they are running. The result is simplicity and a short learning curve for the developer—writing code for 64-bit Windows is just like writing code for 32-bit Windows.
The Windows header files support new data types that allow pointers and pointer-associated variables to reflect the precision of the platform. This means that developers can compile a single source base to run natively on either 32-bit Windows or 64-bit Windows. This strategy reduces the cost of developing applications that leverage 64-bit hardware such as AMD Opteron or Athlon64 processors or Intel Itanium processors.
You will have more time to make your applications 64-bit ready if you adopt the new data-type conventions as soon as possible. If you are changing your code, you should change the data definitions at the same time. Test the application on 32-bit Windows, run it through the 64-bit compiler (described in The Tools), and the application will be ready to test when you have the appropriate 64-bit hardware.