Editing Portable Executable (section)

===Import table===
The ''import address table'' (IAT) is used as a lookup table when the application calls a function in a different module. The [[Dynamic-link library|imports]] can be specified by ordinal or by name. Because a compiled program cannot know the memory locations of its dependent libraries beforehand, an indirect jump is necessary for API calls. As the dynamic linker holds modules and resolves dependencies, it populates the IAT slots with actual addresses of the corresponding library functions. Although this adds an extra jump, incurring a performance penalty compared to intermodular calls, it minimizes the number of memory pages that that require [[copy-on-write]] changes, thus conserving memory and disk I/O. If a call is known to be intermodular beforehand (if indicated by a [[Dynamic-link library|dllimport]] attribute), the compiler can generate optimized code with a simple indirect call [[opcode]].<ref name="Peering Inside" />