Introduction to Cobol Programming
COBOL is a third-generation programming language, and one of
the oldest programming languages still in active use.
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Cobol Basics
Coding Areas, Syntax, The
Hello World Program.
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Cobol Divisions
The Four Cobol Divisions.
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The Identification Division
The identification division tells the computer the name of the program and
supplies other documentation concerning the program's author.
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The Environment Division
This division tells the computer what the program will be interacting with
(i.e. its environment) such as printers, disk drives, other files etc.
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Data Division
The data division is where memory space in
the computer is allocated to data and identifiers that are to be used by the
program.
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Procedure Division
The procedure division is where the logic of
the program actually found.
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Defining Data Part 1
A large portion of any COBOL program consists of the data division and how the
data is defined and manipulated.
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Number Formats
There are three types of number formats.
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Moving and Editing Data
Care must be taken when moving (using the MOVE verb) data to an item.
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Initializing Data
During a program run it is often necessary to reset an
item, or group of items, back to zero (or other value), or back to a certain literal.
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Defining Data Part 2
How data is prepared for printing or for writing to a file is largely controlled
by how it is defined in the data division.
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Printing and Writing Data
The specific commands used for printing or writing data
are given in the Commands and logic sections.
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Tables
Also known as an array in other languages, a table is a
group of data associated with a single item name.
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Boolean Data
Boolean data is either TRUE or FALSE.
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HIGH-VALUES and LOW-VALUES
There are occasions when you may wish to set a variable to
an infinitely high or infinitely low number.
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Commands and Logics
Commands and Logics
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Accept and Display
To enter data via the console during a program run, use
the ACCEPT verb.
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Move
The MOVE statement has already been extensively used in the examples in the Defining Data section.
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Perform
The PERFORM verb is one of the most important in COBOL
(alongside MOVE).
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Cobol IF... THEN...ELSE...
Another fundamental part of programming logic is the
ability to offer a choice of what to do that depends on the conditions asked of.
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Conditions
There are four types of conditions that could be tested
either in a PERFORM, IF..THEN, or EVALUATE.
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Cobol Evaluate
If there are a large number of conditional alternatives,
then using a large number of nested IF statements can be messy.
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Cobol Strings
STRING will move a series of strings into a destination
string.
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Cobol Write
To output data to the printer or to a file, the verb WRITE
is used.
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Scope Terminators
In the section
COBOL basics I mentioned the full stop (period).
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File Handling
This section outlines how data can read from and written to files.
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Reading and Writing
In order to either read, alter or create a new file, we must first open it (even if it doesn't even exist yet).
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REWRITE, DELETE, and EXTEND
In order to ammend a record in a file, such as to update
data (see League Table Program
in sample programs section)
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SORT and MERGE
If you wished to take a file of unordered records and produce a new file of these records sorted into ascending or descending order of a field you would use SORT.
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Input and Output Procedure
The SORT statement above sorted all the records in the
file into a new file.
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FILE STATUS (error handling)
A number of errors can occur that result from file
input/output that programmer may wish to be able to deal with in order to avoid unexpected program termination.
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Debugging COBOL Code
Debugging COBOL code
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