1. Structured COBOL Programming
10th edition
John Wiley & Sons, Inc.
Nancy Stern
Hofstra University
Robert A. Stern
Nassau Community College
James P. Ley
University of Wisconsin-Stout
PowerPoint Winifred J. Rex
Presentation Bowling Green State University

2. An Introduction to Structured Program Design in COBOL
Chapter 1
An Introduction to Structured Program Design in COBOL
Please note that the original slides will be modified in a number
of places by your professor.
These changes are for pedagogical reasons.

3. Chapter Objectives To familiarize you with
Why COBOL is a popular business-oriented language.
Programming practices and techniques
History of COBOL
Use of the current ANSI standard versions of COBOL
Four divisions of a COBOL program

4. Chapter Contents Computer Programming: An Overview
Applications Program Development Process
Nature of COBOL
History of COBOL and the ANS Versions
Techniques for Improving Program Design
Sample Programs
Entering and Running a COBOL Program on Your Computer

5. Computer Program
A set of instructions that enables computer to process data
Also called software
Two types of computer programs
Operating system programs - control overall operations of computer
Oftentimes called System Software
Applications programs - perform tasks required by users
Often called Applications Software  Us.

6. Applications Programs
Written by applications programmer
May provide quick solution to one-time problem
Displaying average grade for set of exam scores
Or may be run on regularly scheduled basis
Program to print student transcripts each semester
Program to generate a Payroll
Program to generate and print an Inventory Listing

7. Application Programs - Customized
Written for specific users like doctors, car dealerships
Necessary if user has special requirements

8. Applications Package – General Usage
Written for general user who needs program to perform standard tasks
Standard tasks include budgeting, scheduling payroll, etc.
Cheaper, easier than writing customized program

9. Program Languages Machine language Only language computer understands
All programs executed on computer must be in machine language
Machine language programs difficult to write
Written in binary, such as:
(actual instruction)
(actual instruction in binary)

10. Assembler Languages Level ‘higher’ than Machine Language.
Use mnemonic codes rather than pure binary digits, such as:
L R5,X
AR R5,R4
ST R5,SUM
Each of these instructions translates (normally one-to-one) into a machine language statement (that is, binary…)

11. Program Languages Symbolic language (like COBOL)
Called Higher-Level Languages
English-like languages used to write programs
Easier than writing programs in machine language or assembly languages.
Must be translated or compiled into machine language to run on computer

12. Program Development Process
Determine Program Specifications – the “Whats”
Design Program Using Program Planning Tools – the “Hows.”
Code and Enter Program (using some editor)
Compile Program Implementation
Test Program
Document Program

13. 1. Program Specifications
Systems analysts, users and programmers develop specifications
Specifications include:
Description of input and output data
Description of what the program must do to the input to convert it to the output - that is, WHAT the program is to do.
They may provide formulas, constraints on data, conditions, etc. etc. BUT (again, not How the developers accomplish this!)
In a perfect world, Systems Analysts specify the ‘requirements’ needed. (doesn’t always work this way.)

14. 1. Program Specifications
Record layout forms describe format of input and output data
Data names of each data item in record
Location of each data item in record
Size of each data item
Number of decimal positions (for numeric data items)
Please note that exactly WHO does this may vary depending on the expertise of the systems analysts, developers, etc. But these are part of the Specifications.

15. 1. Program Specifications
Printer spacing charts describe
Spacing of outputs (see pp 6-7)
hard copy reports
screen layouts, etc.
Layout of printed output
Heading, detail, total lines
Error messages and locations…

16. 2. Design the Program
Program planning tools used to map out structure and logic of program
Once specifications are captured (discuss!), design takes place.
Two real kinds of design:
Architectural design (high level, parts; components, blocks of functionality; relationships among these blocks, and
Detail design – the logic inside each block, part, component, etc.

17. 2. Design the Program
Different tools may be used to capture the preliminary (architectural) design as well as the detail (logic; algorithms) design.
Architectural Design:
For many traditional systems, we may use Data Flow Diagrams; Structure Charts, System Flow Charts, and similar technologies
For Detail design:
Most practitioners use flowcharts, pseudocode, HIPO, or other techniques to capture the module logic.

18. Book cites for Detail Design:
Architectural design: Book suggests Hierarchy charts show relationships among sections of program.
We will use these and call them Structure Charts.
Book cites for Detail Design:
Flowcharts use block diagrams to represent logic – a graphical model, and
Pseudo-code uses English-like statements
This one is preferred but some hang on to the flowchart. In some cases, it ‘is’ clearer, though.

19. 3. Code and Enter Program
Programmer writes and enters program into computer
Program written in symbolic language (like COBOL)
Called source program

20. 4. Compile Source Program
Compiler is program that
Checks source program for rule violations
Translates source program into object program
(See p. 8 for System Flow Chart. Know this.)
Source program in symbolic language
Translated by compiler
Object program in machine language

21. 5. Test Program Test or debug program to ensure it contains no errors
Check for two types of errors
Compile-Time Errors
Execution Errors

22. Compile-Time Errors
Errors detected by compiler during translation from COBOL to machine language
Detects violations of programming rules
Misspelled reserved words
Missing punctuation
Errors in use of the programming language
Also called syntax errors

23. Execution Errors Detected when program is run
Logic error causes incorrect output
Sequence of instructions incorrect
Wrong instruction coded
Run-time error if computer cannot execute instruction
Attempt to divide by zero
Attempt to read a file that cannot be found

24. Debugging Techniques Desk checking Correcting syntax errors
always do this. Can be costly to omit.
Correcting syntax errors
Correct syntax errors and resubmit
Program walkthroughs
Sometimes done in teams; good approach
Can be done prior to submitting for compilation.
Executing the program
 Just because a program runs to EOJ, does NOT mean that program was successful!!

25. 6. Document the Program
Documentation - formal set of procedures and instructions to specify how to use program
Written for
Those working with output
Computer operators who run program
Maintenance programmers who make modifications to program
In some circles called: program maintenance manual, operators manual, users manual, etc…

26. Nature of COBOL Business-oriented language Standard language
Great for business data processing
Large volumes of data
Great for data manipulation
No language is better for transaction processing or data manipulation than COBOL
Has other major deficiencies, but not these.
Standard language
English-like language
Multiply hours-worked by rate giving salary
Relatively easy to understand

27. History of COBOL
Developed in 1959 as standard language to meet needs of business
Committee to develop language convened by Department of Defense
Included representatives from academia, business, computer manufacturers

28. Standard Versions of COBOL
1968
1974
1985
wide variations in COBOL compilers
first COBOL standard set by American National Standards Institute (ANSI)
second ANSI standard to make COBOL more efficient, standardized
this ANSI standard incorporated structured programming techniques

29. Current and Future Standards
 currently the most widely used
Sometimes called COBOL 2.
2002+ is next standard
Approval expected in 2002
Information on COBOL standard at

30. Future of COBOL Likely to remain important language
Unlike academic environment, most programs are developed to be used for many years to realize a ROI. This implies the need to maintenance as requirements change and errors are discovered.
Older COBOL programs need to be updated
Still used by many for new program development

31. Use of COBOL About 200 billion lines of COBOL source code in use
5 billion new lines added each year
Used by 42.7% of application programmers in medium to large U.S. companies
$200 million in expected revenues for 2001

32. Year 2000 Problem (Y2K)
Year stored as two digits in older programs to save space
19 assumed as valid prefix for all years
95 represented year 1995
Invalid as prefix for years 2000 and beyond
00 could mean 1900 or 2000

33. Year 2000 Problem (Y2K)
Many calculations with dates incorrect starting in 2000
To find your age if you were born in 1970
Subtract 70 from 95 ( = 25)
Calculation incorrect for year 2000 and beyond
= -70 when age should be 30

34. Year 2000 Problem (Y2K) To correct problem
Billions of lines of code, many written in COBOL needed to be examined
Code changed to use four digits for year
Age, other calculations now correct
= 25
= 30

35. Improving Program Design
Two techniques used to develop programs that are easier to understand, test, debug and modify
Structured Programming
Top-Down Programming

36. Structured Programming
Eliminates use of GO TO statements
Allowed skipping to different sections of program without returning to starting point
Advocated the use of simple program constructs:
sequence
selection
iteration plus two extensions (later)
Program logic easier to follow with "GO-TO-less" programming

37. Structured Programming
Program divided into paragraphs
Main paragraph or module controls logic flow using PERFORM statements
Sometime called a ‘driver’ module…
Main module "performs" other modules when instructions in that module required
Control transferred to a different paragraph and, upon completion of the instructions in that paragraph, control returns to the main paragraph.
Each module can be written and tested independently of others

38. Top-Down Programming
Another technique to make programs easier to understand, test, debug and modify
Develop program like term paper
Develop outline first
Add details for each of main steps
Add further refinement for more complex steps

39. Top-Down Programming For COBOL program
Code main modules or routines first
Code intermediate modules next
Details deferred to minor modules and coded last
We will use this technique a lot later on. We may refer to this technique as ‘drivers’ and ‘stubs.’
This is an outstanding approach to developing larger programs…