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SAS Language Reference: Dictionary |

Definitions |

Packed decimal | specifies a method of encoding decimal numbers by
using each byte to represent two decimal digits. Packed decimal representation
stores decimal data with exact precision. The fractional part of the number
is determined by the informat or format because there is no separate mantissa
and exponent.
An advantage of using packed decimal data is that exact precision can be maintained. However, computations involving decimal data may become inexact due to the lack of native instructions. |

Zoned decimal | specifies a method of encoding decimal numbers in which each digit requires one byte of storage. The last byte contains the number's sign as well as the last digit. Zoned decimal data produces a printable representation. |

Nibble | specifies 1/2 of a byte. |

Types of Data |

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 15 is stored in two nibbles, using the hexadecimal digits 1 and 5.

The sign indication is dependent on your operating environment. On IBM mainframes, the sign is indicated by the last nibble. With formats, C indicates a positive value, and D indicates a negative value. With informats, A, C, E, and F indicate positive values, and B and D indicate negative values. Any other nibble is invalid for signed packed decimal data. In all other operating environments, the sign is indicated in its own byte. If the high-order bit is 1, then the number is negative. Otherwise, it is positive.

The following applies to packed decimal data representation:

- You can use the S370FPD format on all
platforms to obtain the
IBM mainframe configuration.
- You can have unsigned packed data with no sign indicator. The
packed decimal format and informat handles the representation. It is consistent
between ASCII and EBCDIC platforms.
- Note that the S370FPDU format and informat expects to have an
F in the last nibble, while packed decimal expects no sign nibble.

The following applies to zoned decimal data representation:

- A zoned decimal representation stores a decimal digit in the low
order nibble of each byte. For all but the byte containing the sign, the high-order
nibble is the numeric zone nibble (F on EBCDIC and 3 on ASCII).
- The sign can be merged into a byte with a digit, or it can be
separate, depending on the representation. But the standard zoned decimal
format and informat expects the sign to be merged into the last byte.
- The EBCDIC and ASCII zoned decimal formats produce the same printable
representation of numbers. There are two nibbles per byte, each indicated
by a hexadecimal digit. For example, the value 15 is stored in two bytes.
The first byte contains the hexadecimal value F1 and the second byte contains
the hexadecimal value C5.

The following applies to packed Julian dates:

- The two formats and informats that handle Julian dates in packed
decimal representation are PDJULI and PDJULG. PDJULI uses the IBM mainframe
year computation, while PDJULG uses the Gregorian computation.
- The IBM mainframe computation considers 1900 to be the base year,
and the year values in the data indicate the offset from 1900. For example,
98 means 1998, 100 means 2000, and 102 means 2002. 1998 would mean 3898.
- The Gregorian computation allows for 2-digit or 4-digit years.
If you use 2-digit years, SAS uses the setting of the YEARCUTOFF value to
determine the true year.

Platforms Supporting Packed Decimal and Zoned Decimal Data |

Some platforms have native instructions to support packed and zoned decimal data, while others must use software to emulate the computations. For example, the IBM mainframe has an Add Pack instruction to add packed decimal data, but the Intel-based platforms have no such instruction and must convert the decimal data into some other format.

Languages Supporting Packed Decimal and Zoned Decimal Data |

Several different languages support packed decimal and zoned decimal data. The following table shows how COBOL picture clauses correspond to SAS formats and informats.

IBM VS COBOL II clauses |
Corresponding S370Fxxx formats/informats |
---|---|

PIC S9(X) PACKED-DECIMAL | S370FPDw. |

PIC 9(X) PACKED-DECIMAL | S370FPDUw. |

PIC S9(W) DISPLAY | S370ZDw. |

PIC 9(W) DISPLAY | S370ZDUw. |

PIC S9(W) DISPLAY SIGN LEADING | S370FZDLw. |

PIC S9(W) DISPLAY SIGN LEADING SEPARATE | S370FZDSw. |

PIC S9(W) DISPLAY SIGN TRAILING SEPARATE | S370FZDTw. |

For the packed decimal representation listed above, X indicates the
number of digits represented, and W is the number of bytes. For PIC S9(X)
PACKED-DECIMAL, W is

. For PIC 9(X) PACKED-DECIMAL, W is
**ceil((x+1)/2)**

. For example, PIC S9(5) PACKED-DECIMAL represents five digits.
If a sign is included, six nibbles are needed.
**ceil(x/2)**

has a length of three bytes, and the value of W is 3.
**ceil((5+1)/2)**

Note that you can substitute COMP-3 for PACKED-DECIMAL.

In IBM assembly language, the P directive indicates packed decimal, and the Z directive indicates zoned decimal. The following shows an excerpt from an assembly language listing, showing the offset, the value, and the DC statement:

offset value (in hex) inst label directive +000000 00001C 2 PEX1 DC PL3'1' +000003 00001D 3 PEX2 DC PL3'-1' +000006 F0F0C1 4 ZEX1 DC ZL3'1' +000009 F0F0D1 5 ZEX2 DC ZL3'1'

In PL/I, the FIXED DECIMAL attribute is used in conjunction with packed decimal data. You must use the PICTURE specification to represent zoned decimal data. There is no standardized representation of decimal data for the FORTRAN or the C languages.

Summary of Packed Decimal and Zoned Decimal Formats and Informats |

SAS uses a group of formats and informats to handle packed and zoned decimal data. The following table lists the type of data representation for these formats and informats. Note that the formats and informats that begin with S370 refer to IBM mainframe representation.

Format |
Type of data representation |
Corresponding informat |
Comments |
---|---|---|---|

PD | Packed decimal | PD | Local signed packed decimal |

PK | Packed decimal | PK | Unsigned packed decimal; not specific to your operating environment |

ZD | Zoned decimal | ZD | Local zoned decimal |

none | Zoned decimal | ZDB | Translates EBCDIC blank (hex 40) to EBCDIC zero (hex F0), then corresponds to the informat as zoned decimal |

none | Zoned decimal | ZDV | Non-IBM zoned decimal representation |

S370FPD | Packed decimal | S370FPD | Last nibble C (positive) or D (negative) |

S370FPDU | Packed decimal | S370FPDU | Last nibble always F (positive) |

S370FZD | Zoned decimal | S370FZD | Last byte contains sign in upper nibble: C (positive) or D (negative) |

S370FZDU | Zoned decimal | S370FZDU | Unsigned; sign nibble always F |

S370FZDL | Zoned decimal | S370FZDL | Sign nibble in first byte in informat; separate leading sign byte of hex C0 (positive) or D0 (negative) in format |

S370FZDS | Zoned decimal | S370FZDS | Leading sign of - (hex 60) or + (hex 4E) |

S370FZDT | Zoned decimal | S370FZDT | Trailing sign of - (hex 60) or + (hex 4E) |

PDJULI | Packed decimal | PDJULI | Julian date in packed representation - IBM computation |

PDJULG | Packed decimal | PDJULG | Julian date in packed representation - Gregorian computation |

none | Packed decimal | RMFDUR | Input layout is: mmsstttF |

none | Packed decimal | SHRSTAMP | Input layout is: yyyydddFhhmmssth, where yyyydddF is the
packed Julian date; yyyy is a 0-based year from
1900 |

none | Packed decimal | SMFSTAMP | Input layout is: xxxxxxxxyyyydddF, where yyyydddF is the packed Julian date;
yyyy
is a 0-based year from 1900 |

none | Packed decimal | PDTIME | Input layout is: 0hhmmssF |

none | Packed decimal | RMFSTAMP | Input layout is: 0hhmmssFyyyydddF, where yyyydddF is the
packed Julian date; yyyy is a 0-based year from 1900 |

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Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.