Packed-Decimal Format When technology complements business   Description & Discussion

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Introduction
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This document will focus on a discussion of a numeric field (or data string) known as "PACKED-DECIMAL" format (also referred to as packed data or a packed numeric field). This format is used on an IBM Mainframe and is supported by Micro Focus COBOL running on Windows or UNIX.

Note: The items in this document are appropriate for applications that are written in COBOL, Mainframe Assembler (HLASM) or PL/I. The IBM Mainframe architecture drove many of the numeric formats that existed in the early ANSI specifications for COBOL.and have been carried forward to the current COBOL ANSI specifications.

A packed decimal representation stores two decimal digits in one byte. A packed decimal representation stores decimal digits in each "nibble" of a byte. Each byte has two nibbles, and each nibble is indicated by a hexadecimal digit. For example, the value 23 would be stored in two nibbles, using the hexadecimal digits 2 and 3. The sign indication is dependent on your operating environment. On an IBM mainframe, the sign is indicated by the last nibble. The C indicates a positive value, and D indicates a negative value.

The mainframe can perform arithmetic functions on packed-decimal fields without having to convert the format. Storing numeric values in a packed-decimal format may save a significant amount of storage space. For example, on the mainframe the value 12,345 would be five (5) bytes in length (i.e. x'F1F2F3F4F5'). If the same information is stored in a packed-decimal (i.e. USAGE IS COMP-3) the field would be three (3) bytes in length (i.e. x'12345C').

When converting this type of field from EBCDIC to ASCII the programmer is presented with a number of confusing options and challenges. This document will try to explain the options and help the program avoid the common mistakes that are made during a conversion process.

The following table shows the structure of a five digit numeric field using the Packed-Decimal format (i.e. the COBOL syntax would be USAGE IS COMP-3). The field contains a value of one-hundred-twenty-three (or 00123). Since the packed-decimal format stores a digit in each nibble (2 digits per byte) the actual field size is only three (3) bytes.

Note-1: A field that is defined as "Unsigned" (i.e. PIC 99999 COMP-3) is an implied positive value.
Note-2: The "Hex" is an abbreviation for Hexadecimal notation.
Note-3: A field that is defined as "Signed" (i.e. PIC S99999 COMP-3) will have the sign in the rightmost nibble of the units positions (or Byte-2 in the preceding example). A X'nC' is used as an explicit positive sign and a X'nD' is used as an explicit negative sign.
Note-4: The Packed-decimal format is the same for the Mainframe and for Micro Focus running on a Windows or UNIX system.

Table, Packed-Decimal Field Sizes
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The following is a table that shows the actual field sizes (for a COMP-3 or packed-decimal) based on the number of digits specified in the picture clause.

Convert Packed Decimal Fields to Text Strings
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This section describes how to convert the previously discussed packed-decimal formats into text strings to print or display the information in a human readable form. Before converting the packed-decimal fields it should be determined if a conversion is necessary. The following list provides some basic guidelines.

Convert Packed-Decimal to Display
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This section describes how to convert a packed-decimal field (i.e. PIC S9(5) USAGE IS COMPUTATIONAL-3) to a zoned-decimal field (i.e. PIC S9(5) USAGE IS DISPLAY SIGN LEADING SEPARATE). The resulting field will have a separate leading sign but will still have an implied decimal based on the field definition from the COBOL picture clause.

      *    The following defines a signed, packed-decimal field.
      *    The length of this field is 3 bytes & contains 5 digits.
       01  PACK-DECIMAL-S3V2-TEXT.
           05  PACK-DECIMAL-S3V2   pic S9(3)V99 COMP-3 value 0.

      *    The following defines a signed, zone-decimal field.
      *    The sign is not part of the units position because of 
      *    the SIGN LEADING SEPARATE syntax. This is standard 
      *    COBOL coding and is ANSI/85 compliant.
      *    The length of this field is 6 bytes.
       01  SLS-S3V2-TEXT.
           05  SLS-S3V2-NUMB       pic S9(3)V99 value 0
                                   SIGN LEADING SEPARATE.
       ...
       ...

       PROCEDURE DIVISION.

      *    The following statement will place a value into the 
      *    packed-decimal field. The actual value will be x'00123C'.
           add 1.23 to ZERO giving PACK-DECIMAL-S3V2

      *    The following statement will place the arithmetic value of  
      *    the packed-decimal field into the zone-decimal field. The actual  
      *    value will be x'4EF0F0F1F2F3'. This results in converting the 
      *    packed-decimal field. Both fields have an implied decimal point.
           add PACK-DECIMAL-S3V2 to ZERO giving SLS-S3V2-NUMB
      *    The preceding statement is the only statement required to do 
      *    the conversion from packed-decimal to zone-decimal.          
      *    The additional code in this section is used to display the   
      *    input and result field values in hexadecimal dump format.    

Convert Packed-Decimal to Display with Explicit Decimal Point
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This section describes how to convert a packed-decimal field (i.e. PIC S9(5) USAGE IS COMPUTATIONAL-3) to a zoned-decimal field (i.e. PIC X ). The resulting field will have a separate leading sign and an explicit decimal point embedded in the text string. This field (or data string) may easily be exported to a non-COBOL environment.

      *    The following defines a signed, packed-decimal field.
      *    The length of this field is 3 bytes & contains 5 digits.
       01  PACK-DECIMAL-S3V2-TEXT.
           05  PACK-DECIMAL-S3V2   pic S9(3)V99 COMP-3 value 0.

      *    The following defines an edited field for numeric
      *    values and will contain an explicit decimal point. This
      *    is standard COBOL coding and is ANSI/85 compliant.
      *    The length of this field is 7 bytes.
       01  PRINT-LINE.
           05  FILLER              pic X(8) value 'Edited: '.
           05  PRINT-NUMBER        pic +ZZZ.99.
...
...

       PROCEDURE DIVISION.

      *    The following statement will place a value into the 
      *    packed-decimal field. The actual value will be x'00123C'.
           add 1.23 to ZERO giving PACK-DECIMAL-S3V2

      *    The following statement will place the arithmetic value of
      *    the packed-decimal field into the edited print field. The
      *    actual value will be x'4E4040F14BF2F3'. This results in
      *    converting the packed-decimal field but has leading spaces.
           move PACK-DECIMAL-S3V2 to PRINT-NUMBER

      *    The following statement will replace the leading spaces 
      *    with zeroes. The resulting value will be x'4EF0F0F14BF2F3'.
           inspect PRINT-NUMBER replacing all SPACE by ZERO
      *    The preceding 2 statements are the only statements required  
      *    to do the conversion from packed-decimal to zone-decimal.    
      *    The additional code in this section is used to display the   
      *    input and result field values in hexadecimal dump format.    

Space Characters in a Packed, Numeric Field
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We have seen a few instances where a packed field may contain SPACES. This should be considered a bad programming practice. Having non-numeric values in a numeric field should be avoided. The process that caused non-numerics to be placed in a numeric field should be corrected. When converting data between EBCDIC and ASCII this presents an additional effort to deal with the situation.

A SPACE character (hex 40 for EBCDIC or a hex 20 for ASCII) could be a valid numeric entry in a packed field in all the positions of the field except the units positions. It would be reasonable to assume that if the units position of a packed field is a SPACE character and all other positions are SPACE characters then the packed field SPACE values should be converted between EBCDIC and ASCII.

For numeric fields with USAGE IS COMP-3 (i.e. PACKED FIELDS) the conversion code generated by SimoTime does not do any conversion. This is the default behavior. However, since the situation does exist the SimoTime technology has a configuration option to generate conversion code that will analyze a packed field and convert SPACE values between EBCDIC and ASCII or to initialize the packed field with a ZERO value.

The following is sample code that will test a packed field for SPACE values and then convert the EBCDIC SPACE values to ASCII SPACE values.

      *    Packed  CUST-CREDIT-LIMIT
      *    The /PACKEDFLD option is set to SPACECONVERT
           if CUST-RECORD(300:4) = all x'40'
              inspect CUST-RECORD(300:4)   replacing all x'40' by x'20'
           end-if

The following is sample code that will test a packed field for SPACE values and then initialize the packed field to ZERO values.

      *    Packed  CUST-CREDIT-LIMIT
      *    The /PACKEDFLD option is set to SPACEZERO
           if CUST-RECORD(300:4) = all x'40'
              inspect CUST-RECORD(300:4)   replacing all x'40' by x'00'
              move x'0F' to CUST-RECORD(303:1)
           end-if

Summary
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The purpose of this document is to provide an overview of numeric data strings or fields that are packed-decimal format.

Software Agreement and Disclaimer
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Downloads and Links to Similar Pages
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This item will provide a link to  an ASCII or EBCDIC translation table. A column for decimal, hexadecimal and binary is also included.

The following table provides a list of white papers describing the numeric formats used on an IBM Mainframe system. A couple of sample COBOL programs are also included.

The SimoZAPS Utility Program has the capability of generating a COBOL program that will do the conversion of sequential and VSAM (KSDS) files between EBCDIC and ASCII. SimoZAPS can also read a sequential file in EBCDIC format and create an ASCII/CRLF file or VSAM KSDS file in ASCII format. The conversion tables may be viewed or modified to meet unique requirements. The Hexcess/2 function provides the capability of viewing, finding or patching the contents of a file in hexadecimal.

This document provides a quick summary of the  File Status Key  for VSAM data sets and QSAM files.

To review all the information available on this site start at  The SimoTime Home Page .

Glossary of Terms
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Check out  The SimoTime Glossary  for a list of terms and definitions used in the documents provided by SimoTime.

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About SimoTime Enterprises, LLC
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Founded in 1987, SimoTime Enterprises is a privately owned, Limited Liability Corporation located in Novato, California. We specialize in the creation and deployment of business applications using new or existing technologies and services. We have a team of individuals that understand the broad range of technologies being used in today's environments. This includes the smallest thin client using the Internet and the very large mainframe systems. There is more to making the Internet work for your company's business than just having a nice looking WEB site. It is about combining the latest technologies and existing technologies with practical business experience. It's about the business of doing business and looking good in the process. Quite often, to reach larger markets or provide a higher level of service to existing customers it requires the newer Internet technologies to work in a complementary manner with existing corporate mainframe systems. Whether you want to use the Internet to expand into new market segments or as a delivery vehicle for existing business functions simply give us a call or check the web site at http://www.simotime.com