Legacy Languages: : Model COBOL programs with logic examples.

COBOL may be a legacy language, but it's not dead. There are huge numbers of programs written in COBOL that are still running, and running well.
There is no need to rewrite them in another language, since they are working! This book contains generic programs that illustrate major types of logic used in many business programs.
It's not a book about COBOL syntax. It's the sequence of instructions that accomplish the task at hand.
The programs are structured in a top-down kind of logic. The flow of control begins at the beginning, and continues in one direction only, down, using subroutine calls ("PERFORM", or "CALL") to execute procedures, and then return to the major path of program execution flow.
There is such a thing as a "Spaghetti" program, in which the flow of control goes up, down, outside of the current procedure, and anywhere you can imagine. I remember those programs. They were very hard to follow and harder still to maintain. There is no logical method to analyze those programs and to understand them.
This book contains logic structures that are simple and easy to understand. I used these logic structures during much of the time when I was programming.
They were tested during October 2020 on an IBM mainframe computer running z/OS and Enterprise COBOL.
Here are the programs:
1. SEQSIMP1. The Simple, Single File Program
2. SEQRPT1. The Simple, Single File Report Program
3. SEQRPT2. The Simple, Single File Report Program with Record Count or Final Totals
4. SEQCK1. The Sequence Check Program
5. SELECT1. The Record Selection Program
6. VALID1. The Edit or Validate Program
7. BRKLV1. The One Level Subtotal (Control Break) Program
8. BRKLV3. The Three Level Subtotal (Control Break) Program
9. FILEUPD1. The Sequential File, Batch Update Program
10. SORTEX1. The COBOL Sort
11. EVAL1. The CASE Structure: EVALUATE
12. DIRSUB1. Direct Subscripting
13. SERSRCH1. The Sequential Search
14. BINSRCH1. The Binary Search
15. LOADTBL1. Loading a Table from a Sequential File
16. VSAMSEQ1. The VSAM File Read Sequentially
17. VSAMRND1. The VSAM KSDS, Read Randomly
18. VSAMRND2. The VSAM File, Read Randomly Based on Records in a Regular Sequential File
19. VSAMLOD1. VSAM Initial Load
20. VSAMACD1. VSAM File Maintenance (Add, Change, Delete)
21. VSAMSTR1. VSAM Read Sequentially, with START
22. VARWRIT1. Creating a Variable Format File
23. VARREAD1. Reading a Variable Format File
24. VARODOW1. Creating a Variable Format File with Occurs Depending On
25. VARODOR1. Reading a Variable Format File with Occurs Depending On
26. LOADODO1. The Table Load with Occurs Depending On
27. VSAM Error Codes