Two basic issues that regard conversion arise for applications developers:
Data type consistency and the different data models
Interoperation between applications that use different data models
Trying to maintain a single source with as few #ifdefs as possible is usually better than trying to maintain multiple source trees. This chapter provides guidelines for writing code that works correctly in both 32-bit environments and 64-bit environments. At best, the conversion of current code might require only a recompilation and relinking with the 64-bit libraries. However, for those cases where code changes are required, this chapter discusses the tools that help make conversion easier.