TurboIMAGE/XL Database Management System Reference Manual (30391-90012)

66 Chapter3
Defining a Database
Item Part
depends upon the type designator and can be a halfword,abyte,oranibble. A halfword
is 16 bits, a byte is eight bits, and a nibble is four bits or a half-byte.
NOTE In this manual, a word is a 32-bit storage unit and a halfword is a 16-bit
storage unit. One byte is 8-bits.
Table 3-2. describes the type designators and the unit of measure used for each.
A data item must be an integral number of halfwords in length regardless of the type
designator and its unit of measure. In other words, data items of type P, which are
measured in nibbles, must have a sub-item length and sub-item count such that their
product is evenly divisible by 4, because 4 nibbles equal 1 halfword. Data items of type U,
X, or Z, which are measured in bytes, must have a sub-item length and sub-item count
such that their product is an even number. If a data item is defined as U3, it cannot be a
simple item and must have an even numbered sub-item count so that the data item length
is an integral number of halfwords.
A data item cannot exceed 2047 halfwords in length. The entire item, whether simple or
compound, is always handled as a unit by TurboIMAGE/XL.
TurboIMAGE/XL and Program Language Data Types
The type designator, sub-item count, and sub-item length you specify for a data item
defines its length. TurboIMAGE/XL does not perform any conversions of data or examine
the item to check its validity as it is being added to the database. The only data item
values that TurboIMAGE/XL checks are those specified as part of a lock descriptor in calls
to the DBLOCK procedure. Refer to the discussion on DBLOCK in chapter 5. There are no rules
requiring that a specific type of data defined by a programming language must be stored in
Table 3-2. Type Designators
Unit Bits Type\
Designator
Description
Halfword 16-bit E A real (IEEE floating point) number.
I A signed binary integer in 2's complement form.
J Same as I, but QUERY/3000 allows only numbers
conforming to specifications for COBOL II
COMPUTATIONAL data to be entered.
K An absolute binary quantity (no negative values).
R A real (HP 3000 floating point) number.
Nibble 4-bit P A packed decimal number.
Byte 8-bit U An ASCII character string containing no lowercase
alphabetic characters.
X An unrestricted ASCII character string.
Z A zoned decimal format number.