CICS Conceptual Overview

1
CICS Conceptual Overview

• Large Systems Technology

2
CICS Background

• Customer Information and Control System
• An IBM fee-basis program product that can be
  bought in addition to an operating system like VM
  or MVS
• Designed solely to support on-line transactions

3
Pre-CICS

• Prior to CICS there was no way to do I/O in any
  way except batch mode
• With the advent of CICS, on-line systems became
  possible

4
Embedded Code

• CICS works by allowing the programmer to imbed
  special lines of CICS commands in conventional
  programs

COBOL Line COBOL Line COBOL Line COBOL Line COBOL
Line CICS Line CICS Line COBOL Line COBOL Line
COBOL Line CICS Line COBOL Line COBOL Line
5
Macro and Command Level CICS

• Early CICS was called macro-level
• Required programmers to write very obtuse and
  difficult embedded lines of code
• CICS was improved immensely in the early 1980s by
  the introduction of command-level CICS
• Much easier to use and understand

6
Processing CICS Programs

• Programs go through a CICS pre-processor or
  pre-compiler

COBOL Program with Imbedded CICS
CICS Pre- Processor
COBOL Compiler
Object Module -- Ready to Execute
7
Contemporary CICS

• CICS now is available to work with most major
  languages
• CICS packages for PC platforms are also available