The Collaborative International Dictionary
object file \ob"ject file\, object program \ob"ject program\, n. (Computers) A computer program which has been translated into machine language by a compiler and assembler, but not yet linked into an executable program; sometimes called an obj file, because its file name typically has the extension ``obj'' .
An object file is a file containing object code, meaning relocatable format machine code that is usually not directly executable. There are various formats for object files, and the same object code can be packaged in different object files. An object file also works like an Application Extension (.dll).
In addition to the object code itself, object files may contain metadata used for linking or debugging, including: information to resolve symbolic cross-references between different modules, relocation information, stack unwinding information, comments, program symbols, debugging or profiling information.