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
Presentation
Winifred J. Rex
Bowling Green State University
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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.
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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
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Chapter Contents
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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
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Computer Program
 A set of instructions that enables computer to
process data
 Also called software
 Two types of computer programs
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Operating system programs - control overall
operations of computer
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Oftentimes called System Software
Applications programs - perform tasks required
by users

Often called Applications Software  Us.
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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
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Application Programs - Customized
 Written for specific users like doctors, car
dealerships
 Necessary if user has special requirements
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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
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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:
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0001101001010100 (actual instruction)
010110101000000011000100 (actual
instruction in binary)
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Assembler Languages
 Level ‘higher’ than Machine Language.
 Use mnemonic codes rather than pure binary
digits, such as:
L
AR
ST
R5,X
R5,R4
R5,SUM
 Each of these instructions translates
(normally one-to-one) into a machine
language statement (that is, binary…)
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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
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Program Development Process
1. Determine Program Specifications – the
2.
3.
4.
5.
6.
“Whats”
Design Program Using Program Planning
Tools – the “Hows.”
Code and Enter Program (using some editor)
Compile Program
Implementation
Test Program
Document Program
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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.)
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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.
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1. Program Specifications
Printer spacing charts describe
 Spacing of outputs (see pp 6-7)
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hard copy reports
screen layouts, etc.
 Layout of printed output
 Heading, detail, total lines
 Error messages and locations…
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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:
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Architectural design (high level, parts;
components, blocks of functionality;
relationships among these blocks, and
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Detail design – the logic inside each
block, part, component, etc.
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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:
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For many traditional systems, we may use Data
Flow Diagrams; Structure Charts, System Flow
Charts, and similar technologies
 For Detail design:
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Most practitioners use flowcharts, pseudocode,
HIPO, or other techniques to capture the module
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 Architectural design: Book suggests
Hierarchy charts show relationships among
sections of program.
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We will use these and call them Structure
Charts.
 Book cites for Detail Design:
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Flowcharts use block diagrams to represent
logic – a graphical model, and
Pseudo-code uses English-like statements
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This one is preferred but some hang on to the
flowchart. In some cases, it ‘is’ clearer, though.
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3. Code and Enter Program
 Programmer writes and enters program into
computer
 Program written in symbolic language (like
COBOL)
 Called source program
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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
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5. Test Program
 Test or debug program to ensure it contains
no errors
 Check for two types of errors
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Compile-Time Errors
Execution Errors
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Compile-Time Errors
 Errors detected by compiler during translation
from COBOL to machine language
 Detects violations of programming rules
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Misspelled reserved words
Missing punctuation
Errors in use of the programming language
 Also called syntax errors
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Execution Errors
 Detected when program is run
 Logic error causes incorrect output
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Sequence of instructions incorrect
Wrong instruction coded
 Run-time error if computer cannot execute
instruction
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Attempt to divide by zero
Attempt to read a file that cannot be found
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Debugging Techniques
 Desk checking
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always do this. Can be costly to omit.
 Correcting syntax errors
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Correct syntax errors and resubmit
 Program walkthroughs
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Sometimes done in teams; good approach
Can be done prior to submitting for compilation.
 Executing the program
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 Just because a program runs to EOJ, does
NOT mean that program was successful!!
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6. Document the Program
 Documentation - formal set of procedures
and instructions to specify how to use
program
 Written for
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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…
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Nature of COBOL
 Business-oriented language
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Great for business data processing
Large volumes of data
Great for data manipulation
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No language is better for transaction processing
or data manipulation than COBOL
Has other major deficiencies, but not these.
 Standard language
 English-like language
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Multiply hours-worked by rate giving salary
 Relatively easy to understand
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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
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Standard Versions of COBOL
 1960s
 wide variations in COBOL compilers
 1968
 first COBOL standard set by American
National Standards Institute (ANSI)
 1974
 1985
 second ANSI standard to make COBOL
more efficient, standardized
 this ANSI standard incorporated
structured programming techniques
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Current and Future Standards
  1985 currently the most widely used
 Sometimes called COBOL 2.
 2002+ is next standard
 Approval expected in 2002
 Information on 2002+ COBOL standard at
http://www.ansi.org
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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
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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
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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
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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 (95 - 70 = 25)
 Calculation incorrect for year 2000 and
beyond
00 - 70 = -70 when age should be 30
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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
1995 - 1970 = 25
2000 - 1970 = 30
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Improving Program Design
Two techniques used to develop programs that
are easier to understand, test, debug and
modify
 Structured Programming
 Top-Down Programming
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Structured Programming
 Eliminates use of GO TO statements
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Allowed skipping to different sections of
program without returning to starting point
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Advocated the use of simple program
constructs:
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sequence
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selection
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iteration plus two extensions (later)
 Program logic easier to follow with "GO-TO-
less" programming
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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
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Top-Down Programming
 Another technique to make programs easier
to understand, test, debug and modify
 Develop program like term paper
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Develop outline first
Add details for each of main steps
Add further refinement for more complex steps
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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…
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