A state in which source control software has been unable to integrate changes made by several developers to the same text file (such as a program) when the file is being checked in. For example, a merge conflict might occur if two developers make changes to the same line in the same program; when the second developer attempts to check in the file, a merge conflict is reported. When a merge conflict occurs, the source control software creates a version of the file in which the current version and the changes it was unable to integrate are marked (the exact means of marking depends on the source control software). The developer whose changes could not be integrated must edit the file to manually integrate changes, test it, and then check it in again.