COBOL Tutorial

Data Types and Representation in COBOL

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Numeric Data Representation and Formats

COBOL provides several ways to represent numeric data, each with its own characteristics and uses.

External Decimal (DISPLAY)

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01 EXT-DEC-FIELD PIC 9(5) USAGE DISPLAY.

Default if USAGE is not specified
Each digit uses one byte of storage
Stored as character data (e.g., "12345")
Human-readable in memory dumps
Less efficient for calculations

Binary (COMP, COMP-4, BINARY)

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01 BINARY-FIELD PIC 9(5) USAGE COMP.

Stored in binary format
More efficient for calculations
Uses less storage than DISPLAY
PIC 9(1) to 9(4): 2 bytes
PIC 9(5) to 9(9): 4 bytes
PIC 9(10) to 9(18): 8 bytes

Packed Decimal (COMP-3)

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01 PACKED-FIELD PIC 9(5) USAGE COMP-3.

Stores 2 digits per byte plus sign
PIC 9(5) uses 3 bytes of storage
Efficient storage and calculation
Common on mainframe systems
Each byte contains two 4-bit nibbles

Floating Point (COMP-1, COMP-2)

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01 FLOAT-SINGLE PIC 9(9) USAGE COMP-1.
01 FLOAT-DOUBLE PIC 9(18) USAGE COMP-2.

COMP-1: Single precision (4 bytes)
COMP-2: Double precision (8 bytes)
For scientific calculations
PICTURE clause is ignored
Can handle very large or small values

Alphanumeric Data Handling

Alphanumeric data in COBOL can contain any character in the character set, including letters, numbers, and special characters.

Alphanumeric Data Types

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01 ALPHA-X       PIC X(10).          *> Any character
01 ALPHA-A       PIC A(10).          *> Alphabetic only
01 ALPHA-MIXED   PIC X(5)A(5).       *> Mixed format
01 ALPHA-EDIT    PIC X(5)/X(5).      *> With editing

PIC X: Can contain any character
PIC A: Can contain only letters and spaces
PIC 9: Can contain only numeric digits (when used for display)
Editing characters can be included for formatting

Common Operations

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MOVE "HELLO"     TO ALPHA-X.       *> Simple assignment
MOVE SPACES      TO ALPHA-X.       *> Initialize with spaces
MOVE "12345"     TO ALPHA-X.       *> Numbers as text
IF ALPHA-A IS ALPHABETIC           *> Conditional test
    DISPLAY "Contains only letters and spaces".
STRING "Hello " "World" DELIMITED BY SIZE 
    INTO ALPHA-X.                  *> String concatenation

Signed Numbers Handling

COBOL provides mechanisms for representing signed numbers through the PICTURE clause and specific USAGE options.

Defining Signed Numbers

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01 SIGNED-DISP   PIC S9(5)     USAGE DISPLAY.
01 SIGNED-COMP   PIC S9(5)     USAGE COMP.
01 SIGNED-COMP3  PIC S9(5)     USAGE COMP-3.
01 UNSIGNED-NUM  PIC 9(5).     *> No sign

The 'S' in the PICTURE clause indicates that the field can hold a sign (positive or negative).

Sign Representation

DISPLAY: Sign is typically stored in the rightmost byte (overpunch)
COMP: Sign is part of the binary representation
COMP-3: Sign is stored in the rightmost nibble (C=positive, D=negative)
The SIGN clause can control sign position: SIGN IS LEADING or SIGN IS TRAILING
The SIGN clause can also control sign representation: SIGN IS SEPARATE

Examples with Different Sign Representations

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01 TRAIL-SEPARATE PIC S9(5)  SIGN TRAILING SEPARATE.
01 LEAD-SEPARATE  PIC S9(5)  SIGN LEADING SEPARATE.
01 TRAIL-COMBINED PIC S9(5)  SIGN TRAILING.
01 LEAD-COMBINED  PIC S9(5)  SIGN LEADING.
 
*> For value -12345:
*> TRAIL-SEPARATE would be stored as: "12345-"
*> LEAD-SEPARATE would be stored as: "-12345"
*> TRAIL-COMBINED would have the sign combined with the last digit
*> LEAD-COMBINED would have the sign combined with the first digit

Decimal Point Alignment

In COBOL, the decimal point is not physically stored in the data but is defined by the PICTURE clause.

Using the V Symbol

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01 AMOUNT-1       PIC 9(5)V99.    *> 5 digits before, 2 after decimal
01 AMOUNT-2       PIC 9(3)V9(3).  *> Alternative notation
01 DISPLAY-AMOUNT PIC Z(4)9.99.   *> For display with actual decimal point

The V indicates the position of an assumed decimal point
No actual decimal point is stored in memory
For display, you need a separate field with an actual decimal point

Decimal Alignment in Operations

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01 PRICE          PIC 9(3)V99  VALUE 012.50.
01 QUANTITY       PIC 9(3)     VALUE 003.
01 TOTAL          PIC 9(5)V99.
 
MULTIPLY PRICE BY QUANTITY GIVING TOTAL.
*> TOTAL will contain 0037.50 (internally stored as 003750)

COBOL automatically handles decimal alignment during arithmetic operations.

P Symbol for Assumed Decimal Scaling

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01 LARGE-VALUE    PIC 9(3)P(2).  *> Multiplies value by 100 (adds 2 zeros)
01 SMALL-VALUE    PIC VP(2)9(3). *> Divides value by 100 (0.01234)

The P symbol represents an assumed zero digit
Used for scaling factors when no storage is needed for those positions
Trailing P: Multiplies the value (shifts decimal right)
Leading P: Divides the value (shifts decimal left)

Handling Special Characters

COBOL provides several techniques for handling special characters in data.

Special Characters in Literals

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01 TEXT-FIELD     PIC X(20).
 
*> Single quote in a double-quoted literal
MOVE "John's Book" TO TEXT-FIELD.
 
*> Double quote in a single-quoted literal
MOVE 'Say "Hello"' TO TEXT-FIELD.
 
*> Quotation mark figurative constant
MOVE QUOTE TO TEXT-FIELD(1:1).

Currency and Other Symbols

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01 AMOUNT         PIC $$,$$9.99.
01 CUSTOM-CURR    PIC X(10).
 
*> Currency symbol from SPECIAL-NAMES
MOVE 123.45 TO AMOUNT.  *> Shows as $  123.45
 
*> Custom currency character
MOVE '€123.45' TO CUSTOM-CURR.

SPECIAL-NAMES for Character Customization

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ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SPECIAL-NAMES.
    CURRENCY SIGN IS "€"
    DECIMAL-POINT IS COMMA.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 EURO-AMOUNT    PIC €€€.€€9,99.
 
*> With these settings, €123,45 will be displayed instead of $123.45

The SPECIAL-NAMES paragraph allows customization of currency symbols and decimal point characters.

Inspecting and Manipulating Special Characters

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01 INPUT-TEXT     PIC X(50).
01 OUTPUT-TEXT    PIC X(50).
01 TALLY-COUNT    PIC 9(3).
 
*> Replace all special characters with spaces
INSPECT INPUT-TEXT
   REPLACING ALL "!" BY SPACE
              ALL "@" BY SPACE
              ALL "#" BY SPACE
              ALL "$" BY SPACE.
 
*> Count occurrences of a special character
INSPECT INPUT-TEXT
   TALLYING TALLY-COUNT FOR ALL "@".
 
*> Convert special characters to a string
STRING INPUT-TEXT DELIMITED BY "@"
       INTO OUTPUT-TEXT.

Exercise: Working with Data Types

Complete the following COBOL program to properly handle different data types:

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IDENTIFICATION DIVISION.
PROGRAM-ID. DATATYPES.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  SALES-DATA.
    05  PRODUCT-ID          PIC X(5).
    05  QUANTITY            PIC 9(3).
    05  UNIT-PRICE          PIC 9(3)V99.
    05  DISCOUNT-PERCENT    PIC 9(2)V9.
    05  TAX-RATE            PIC V999.
    
01  CALCULATION-FIELDS.
    05  SUBTOTAL            PIC 9(5)V99.
    05  DISCOUNT-AMOUNT     PIC 9(4)V99.
    05  TAX-AMOUNT          PIC 9(4)V99.
    05  TOTAL-PRICE         PIC 9(5)V99.
    
01  DISPLAY-FIELDS.
    05  DISPLAY-SUBTOTAL    PIC $Z,ZZ9.99.
    05  DISPLAY-DISCOUNT    PIC $Z,ZZ9.99.
    05  DISPLAY-TAX         PIC $Z,ZZ9.99.
    05  DISPLAY-TOTAL       PIC $Z,ZZ9.99.
 
PROCEDURE DIVISION.
    MOVE "AB123" TO PRODUCT-ID.
    MOVE 10 TO QUANTITY.
    MOVE 24.95 TO UNIT-PRICE.
    MOVE 15.0 TO DISCOUNT-PERCENT.
    MOVE .075 TO TAX-RATE.
    
    *> Calculate subtotal (quantity * unit price)
    
    *> Calculate discount amount (subtotal * discount percentage / 100)
    
    *> Calculate tax amount (subtotal - discount) * tax rate
    
    *> Calculate total price (subtotal - discount + tax)
    
    *> Move numeric values to display fields
    
    *> Display the results
    DISPLAY "Product: " PRODUCT-ID.
    DISPLAY "Quantity: " QUANTITY.
    DISPLAY "Unit Price: $" UNIT-PRICE.
    DISPLAY "Subtotal: " DISPLAY-SUBTOTAL.
    DISPLAY "Discount: " DISPLAY-DISCOUNT.
    DISPLAY "Tax: " DISPLAY-TAX.
    DISPLAY "Total: " DISPLAY-TOTAL.
    
    STOP RUN.

Complete the calculation logic and ensure proper numeric handling.

Knowledge Check

Test Your Knowledge

1. How are signed numbers represented in COBOL?

Using the S in the PICTURE clause
Using the SIGNED clause
Using negative values in the VALUE clause
All numbers are signed by default

2. Which of the following PICTURE clauses correctly represents a field that can store dollar amounts up to $9,999.99?

PIC 9(4)V99
PIC $9,999.99
PIC $9(4).9(2)
PIC Z,ZZZ.99

3. In COBOL, where is the decimal point actually stored in numeric data?

As a physical decimal point character in the data
It is not stored; its position is defined by the PICTURE clause
In a separate metadata field
As a special byte marker

4. How would you define a numeric field to store a signed value with 5 digits to the left of the decimal and 2 to the right?

PIC S9(5)V99
PIC S9(5).9(2)
PIC S9(5)-9(2)
PIC S99999V99

5. Which of the following statements about alphanumeric data in COBOL is true?

Alphanumeric fields can only store letters and numbers
Alphanumeric fields automatically convert lowercase to uppercase
Alphanumeric fields can store any character in the character set
Alphanumeric fields require a specific encoding directive

Frequently Asked Questions

VALUE Clause OCCURS Clause

COBOL Tutorial

Data Types and Representation in COBOL

Numeric Data Representation and Formats

External Decimal (DISPLAY)

Binary (COMP, COMP-4, BINARY)

Packed Decimal (COMP-3)

Floating Point (COMP-1, COMP-2)

Alphanumeric Data Handling

Alphanumeric Data Types

Common Operations

Signed Numbers Handling

Defining Signed Numbers

Sign Representation

Examples with Different Sign Representations

Decimal Point Alignment

Using the V Symbol

Decimal Alignment in Operations

P Symbol for Assumed Decimal Scaling

Handling Special Characters

Special Characters in Literals

Currency and Other Symbols

SPECIAL-NAMES for Character Customization

Inspecting and Manipulating Special Characters

Exercise: Working with Data Types

Knowledge Check

Test Your Knowledge

Frequently Asked Questions

What is the difference between DISPLAY and COMPUTATIONAL usage in COBOL?

How does COBOL handle numeric overflow?

Can I perform arithmetic operations on alphanumeric fields?

How does COBOL handle negative zeros?

What encoding is used for COBOL character data?