Why are DDNAMES used in COBOL and JCL?

Answer 1

DD statements in JCL are used to tell which data set names are to be used in your job. In the COBOL program that is executed by a particular step in JCL, you define what your input and output files are in the FILE-CONTROL paragraph of your ENVIRONMENT DIVISION. You give a file name that you will use in your COBOL program that is defined in the FILE SECTION of the DATA DIVISION and assign it to the DDNAME used in your JCL.