How does MVS Operating System think about Programs?

How does MVS Operating System think about Programs?

All COBOL programs(whether your own program, or pre-written & ready-made utility) refer to the input and output files that they access, not by the actual(physical) file name, but using a short symbolic name. The short (alias) symbolic name merely refers to the actual file name values. Through JCL, you will be attaching the actual physical file-names to the symbols. 

The IBM Utility – IEBGENER expects 4 files :
Symbolic file name     Description
1. SYSUT1              Where IEBGENER expects to read Input Data
2. SYSUT2              Where IEBGENER expects to write Output Data
3. SYSIN               Where IEBGENER expects to receive any special and optional instructions
4. SYSPRINT            Where IEBGENER expects to write a simple report, about the task it’s done for you, whether it got completed successfully or not, and much more.