Diff

Diff is a class of programming utilities that compares two or more files for changes or differences between them and frequently offer methods to merge one or more files together as well. This tool is both available as a separate utility but is frequently also embedded into IDE's and text editors.

Diff as a file format
In the UNIX world diff is also a file format used by diff applications for their output, this is seldom used by applications that are native to OS/2 or Microsoft Windows but does show up in apps that are ported from one of the UNIX like systems. Although many newer diff tools have modified the output file format for more flexibility, the original diff output file format has become something of a standard since a number of utilities and systems can open up diff files for further processing or visualisation.

OS/2 diff tools

 * Araxis PMDiff - last version 4.0c freeware
 * GNU diffutils - Open source - Discontinued

Java diff tools

 * Guiffy - Commercial - Current

OS/2 text & programmers editors with diff file support

 * Elvis - diff syntax support included by default - Open source - Current
 * FTE - Has support for syntax highlighting, code folding and syntax-aware autoindent.

DOS text & programmers editors with diff file support

 * Elvis - diff syntax support included by default - Open source - Current
 * FTE - Has support for syntax highlighting, code folding and syntax-aware autoindent.