COBOL Character Set and COBOL Words

Learning goals

After studying this lesson, learners should be able to:

1. Identify the basic COBOL character set.
2. Distinguish between user-defined words and reserved words.
3. Apply naming rules for files, records, and data fields.
4. Read a basic average-grade COBOL example.

COBOL character set

Traditional COBOL uses letters, digits, spaces, and selected special symbols.

Types of COBOL words

COBOL words can be grouped into two major categories:

1. User-defined words - names created by the programmer.
2. Reserved words - words that already have a defined meaning in COBOL.

User-defined words

A user-defined word is a name chosen by the programmer. It may name a file, record, field, paragraph, section, or program.

Rules for user-defined words:

• Use only letters, digits, and hyphens.
• Do not use spaces.
• Do not begin or end with a hyphen.
• Include at least one letter.
• Keep the name within the allowed length; many COBOL references use a 30-character limit.
• Do not use a COBOL reserved word.

Examples:

Reserved words

A reserved word has a built-in COBOL meaning. Programmers cannot freely reuse it as a data name or file name.

Reserved words include:

• Keywords: Required words in a statement, such as READ, AT END, STOP RUN, MOVE, and DISPLAY.
• Optional words: Words that improve readability but may not be required by the compiler in some formats.
• Figurative constants: Reserved words representing common values, such as ZERO, ZEROS, ZEROES, SPACE, SPACES, QUOTE, and QUOTES.

Example:

READ MASTER-FILE AT END
    MOVE 1 TO EOF-SW.

In this example, READ, AT END, and MOVE are COBOL words. MASTER-FILE and EOF-SW are user-defined names.

Figurative constants

Figurative constants are readable substitutes for common values.

Example:

MOVE ZEROS TO TOTAL-SALES.
MOVE SPACES TO CUSTOMER-NAME.

Average-grade case study

A simple COBOL exercise can ask the program to:

1. Accept a student's name.
2. Accept a midterm grade.
3. Accept a final grade.
4. Compute the average.
5. Display the average.
6. Ask whether another record should be entered.

A generic screen layout might be:

ENTER NAME: __________
ENTER MIDTERM GRADE: __________
ENTER FINAL GRADE: __________
AVERAGE: __________
INPUT MORE? (Y/N): __________