COBOL CONCEPT

What Is COBOL?

COBOL is a programming language especially aimed at solving business problems. You will see as you work through this book that COBOL solves a lot more than just business problems and can be used as a solution to many data processing problems.

New Term: COBOL is an acronym for Common Business Oriented Language.

NOTE: COBOL was developed by the Conference on Data Systems Languages (CODASYL), convened in 1959 by the Department of Defense. COBOL compilers became available in 1960, but they were not standardized. The American National Standards Institute (ANSI) standardized a version of COBOL in 1968. The language was revised and updated by ANSI in 1974 and again in 1985. These standards sometimes are called COBOL or COBOL-68, COBOL-74, or COBOL-85. Most compilers are now COBOL-85 standard, but there still are a few COBOL-74 versions out there. This book is written against the COBOL-85 standard, but you will have no trouble using a COBOL-74 compiler for any of the examples.

Because the year 2000 problem might be one of the reasons that you are studying this book, it is worth noting that legacy code could be written in any of the earlier COBOL standards. If you are taking this course to bring yourself up to speed for an update effort, you will need to learn the quirks and differences of the particular COBOL version that you will be working on. This book covers the core of COBOL-85 and will give you about 95% of any version of COBOL that you might work with. Throughout the book there are tips on differences that you might find in other versions of COBOL.

The future of COBOL is fairly bright. A new COBOL standard is being drafted even as I write this. This standard is intended to take COBOL into the future and certainly well beyond the year 2000. The amount of money that is being invested in correcting date problems in existing COBOL code is a sure indicator that no one is planning to dispose of COBOL in the near future.

Approximately 90% of all COBOL code runs in a character-based environment, which means that most COBOL screens are 80 columns wide by 24 or 25 characters high and do not contain graphics. Although there are versions of COBOL on the market that act in a Windows-like environment, this book is not intended to be a course in COBOL for Windows. This means that throughout the book, you will be running or executing your programs on an MS-DOS computer or in an MS-DOS window that has been opened on a Windows computer. The MS-DOS window is an 80 x 24 character window and represents the kind of display that you might see when coding COBOL on a mainframe or minicomputer.

A computer processes numbers and is made up of a central processing unit, input devices, output devices, main memory, and secondary storage.
A computer can't do anything without a program.
A program is a series of instructions that the central processing unit executes to process data, usually using some input data and providing some sort of output.
A programming language is a method of writing a source code file in an English-like language that a human being can understand.
A compiler translates the source code file into instructions that the central processing unit can understand and execute.
A COBOL program contains four DIVISIONs: the IDENTIFICATION DIVISION, the ENVIRONMENT DIVISION, the DATA DIVISION, and the PROCEDURE DIVISION.
A DIVISION can be broken down into paragraphs. Some divisions have required paragraphs, such as the PROGRAM-ID paragraph in the IDENTIFICATION DIVISION.
The names of the paragraphs in the PROCEDURE DIVISION are assigned by the programmer.
The work of a COBOL program is done in sentences that contain the commands of a program and appear within a paragraph.
A COBOL program is written in 80-column format. The columns are divided into the following areas:
- Columns 1 through 6 are the sequence area and can be used by the programmer for line numbering. Line numbering is optional.
- Column 7 is the indicator area. An asterisk (*) in column 7 causes everything to the right of the asterisk to be treated as a comment.
- Columns 8 through 11 are Area A, and columns 12 through 72 are Area B. DIVISION names, SECTION names, and paragraph names must begin in Area A, but they can extend into Area B. Sentences begin and end in Area B.
- Columns 73 through 80 are undefined and are not processed by the COBOL compiler, but some COBOL editors use these columns to tag lines with modification codes.

Today, you also learned how to type, compile, and run several simple COBOL programs.

Q&A

Q Why is so much of COBOL in uppercase?

A COBOL was developed in the days when computer terminals and keypunch machines used only uppercase letters. The entire language was defined in terms of this all-uppercase state of affairs. You can display uppercase and lowercase messages, such as Hello world, because terminals now have uppercase and lowercase capability. However, the actual elements of COBOL--the DIVISIONs, the paragraph names such as PROGRAM-BEGIN, and the verbs such as DISPLAY--originally were designed in uppercase only.

Q What does a blank line in a program do?

A Nothing. The compiler skips blank lines. You can put blank lines anywhere you want in the program to improve readability.

Q Does COBOL use line numbers?

A Yes, but they are optional. Most compilers ignore them or can be set to ignore them. Some compilers on larger computers will process the line numbers and provide a warning if the line numbers are out of sequence, but this is not an error.

Q Can I put anything in a comment?

A Yes. As long as the asterisk appears at column 7, everything after the asterisk is ignored and has no effect on the compiler. You can write English sentences or gobbledygook, although the usual practice is to provide some information that describes what the program is doing, or why it is doing it.

You can do this on as many lines as necessary to complete the comment.

Q Will my comments appear in the program when it runs?

A No. Comments appear only in the source code file, and they will not be included in the compiled program. Comments are intended to document the source code. The computer can read only the compiled code, and the comments wouldn't mean anything to the computer, so they are not included in the resulting program.

Q Why do paragraph names have hyphens in them?

A Paragraph names in COBOL are limited to 30 characters and may only contain uppercase letters (A through Z), digits (0 through 9), and the hyphen (-). The hyphen is used to improve the readability of paragraphs and the names of data (which is covered in Day 2). Some modern compilers allow paragraph names, division names, and other elements of COBOL to be typed in lowercase.

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