For an account of the concept of object language in mathematical logic, see formal system.

In computer science, an object language is a programming language that a programmer codes in. In order for the machine to run the code the programmer writes, it has to be compiled, assembled, and interpreted. In the process, code itself becomes other intermediate languages (such as assembly language) before becoming a binary program that the computer can run.

The languages the code becomes during these intermediate stages and the final machine language are referred to as metalanguages.