Binary compatibility

Two or more pieces of code are binary compatible if they can be used together after compilation. In most cases the term refers to modifications in a project - a change is said to maintain binary compatibility if it does not require unaltered code to be compiled again.

Most large open source projects insist that contributions maintain binary compatibility, at least between major revisions. This means you can't change anything that would require the whole project to be recompiled.

In some high-level languages like Java this is not an issue because source compatibility guarantees binary compatibility.