(Customer Information Control System) A TP monitor from IBM that was originally developed to provide transaction processing for IBM mainframes. It controls the interaction between applications and users and lets programmers develop screen displays without detailed knowledge of the terminals used. It provides terminal routing, password security, transaction logging for error recovery and activity journals for performance analysis.

CICS has also been made available on non-mainframe platforms including the RS/6000, AS/400 and OS/2-based PCs.

CICS commands are written along with and into the source code of the applications, typically COBOL, although assembly language, PL/I and RPG are also used. CICS implements SNA layers 4, 5 and 6.