REXX (REstructured eXtended eXecutor) is an interpreted programming language developed at IBM by Mike Cowlishaw. It is a structured, high-level programming language designed for ease of learning and reading. Proprietary and open source REXX interpreters exist for a wide range of computing platforms; compilers exist for IBM mainframe computers.
Rexx is widely used as a glue language, macro language, and is often used for processing data and text and generating reports; these similarities with Perl mean that Rexx works well in Common Gateway Interface (CGI) programming and it is indeed used for this purpose. Rexx is the primary scripting language in some operating systems, e.g. OS/2, MVS, VM, AmigaOS, and is also used as an internal macro language in some other software, e.g., KEDIT, THE, the ZOC terminal emulator. Additionally, the Rexx language can be used for scripting and macros in any program that uses Windows Scripting Host ActiveX scripting engines languages (e.g. VBScript and JScript) if one of the Rexx engines (see below) are installed.
Rexx is supplied with VM/SP on up, TSO/E Version 2 on up, OS/2 (1.3 on up), AmigaOS Version 2 on up, PC DOS (7.0 or 2000), and Windows NT 4.0 (Resource Kit: Regina). REXX scripts for OS/2 and NT-based Windows share the filename extension .cmd with other scripting languages, and the first line of the script specifies the interpreter to be used.
A Rexx script or command is sometimes referred to as an EXEC in a nod to Rexx's role as a replacement for the older EXEC command language on CP/CMS and VM/370 and EXEC 2 command language on VM/SP.