Application programming on z/OS
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COBOL on z/OS

Application programming on z/OS

Common Business-Oriented Language (COBOL) is a programming language similar to English that is widely used to develop business-oriented applications in the area of commercial data processing.

COBOL has been almost a generic term for computer programming in this kind of computer language. However, as used in this section, COBOL refers to the product IBM® Enterprise COBOL for z/OS® and OS/390®.

In addition to the traditional characteristics provided by the COBOL language, this version of COBOL is capable, through COBOL functions, of integrating COBOL applications into Web-oriented business processes. With the capabilities of this release, application developers can do the following:
  • Utilize new debugging functions in Debug Tool
  • Enable interoperability with Java™ when an application runs in an IMS™ Java-dependent region
  • Simplify the componentization of COBOL programs and enable interoperability with Java components across distributed applications
  • Promote the exchange and usage of data in standardized formats including XML and Unicode.

With Enterprise COBOL for z/OS and OS/390, COBOL and Java applications can interoperate in the e-business world.

The COBOL compiler produces a program listing containing all the information that it generated during the compilation. The compiler also produces information for other processors, such as the binder.

Before the computer can execute your program, the object deck has to be run through another process to resolve the addresses where instructions and data will be located. This process is called linkage edition and is performed by the binder.

The binder uses information in the object decks to combine them into load modules. At program fetch time, the load module produced by the binder is loaded into virtual storage. When the program is loaded, it can then be run. Figure 1 illustrates the process of translating the COBOL source language statements into an executable load module.

This process is similar to that of Assembler language programs. In fact, this same process is used for all of the HLLs that are compiled.

Figure 1. HLL source to executable module
HLL source to executable module
  • COBOL program format
    With the exception of the COPY and REPLACE statements and the end program marker, the statements, entries, paragraphs, and sections of a COBOL source program are grouped into four divisions.
  • COBOL relationship between JCL and program files
    We can achieve device independence through a combination of JCL statements and the COBOL program.
  • Running COBOL programs under UNIX
    To run COBOL programs in the UNIX® environment, you must compile them with the Enterprise COBOL or the COBOL for OS/390 and VM compiler. They must be reentrant, so use the compiler and binder option RENT.
  • Communicating with Java methods
    A COBOL program can interoperate with JAVA.
  • Creating a DLL or a DLL application
    A dynamic link library or DLL is a file that contains executable code and data that is bound to a program at run-time. The code and data in a DLL can be shared by several applications simultaneously. Creating a DLL or a DLL application is similar to creating a regular COBOL application. It involves writing, compiling, and linking your source code.
  • Structuring OO applications
    You can structure applications that use object-oriented COBOL syntax in one of three ways.
  • More information about the COBOL language
    You should know about COBOL standards, input and output, data structures, and program types.
  • Targeting COBOL programs for certain environments
    COBOL programs can run in CICS®, DB2®, and IMS environments.
Parent topic: Programming languages on z/OS
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