Describes the starting address of a memory mapped EXE or DLL.
Windows uses the base address of a module as the module's instance handle (HINSTANCE).
Base address is commonly used in connection with the RVA (Relative Virtual Address) which are summed together to point some place in file which was mapped to memory.
Default base address for Win32 Executables is 0x400000h, for DLLs 0x10000000h.
This default address can be changed by setting one of the linker option (/BASE:{ address | @ filename , key }).
If sufficient space is not available at this address, the system relocates the program.
To prevent relocation, /FIXED option should be used.