The data item is stored in character form, 1 character for each 8-bit byte. This corresponds to the format used for printed output. DISPLAY can be explicit or implicit.
USAGE IS DISPLAY is valid for the following types of items:
+-------------------------------IBM Extension--------------------------------+
+----------------------------End of IBM Extension----------------------------+
+-------------------------------IBM Extension--------------------------------+
For conditional expressions, the class condition cannot be used for external floating-point data items, which have a USAGE DISPLAY.
+----------------------------End of IBM Extension----------------------------+
Alphabetic, alphanumeric, alphanumeric-edited, and numeric-edited items are discussed in Data Categories and PICTURE Rules.
The PICTURE character-string of a zoned item can contain only 9s, the operational sign symbol S, the assumed decimal point V, and one or more Ps.
External decimal items are sometimes referred to as zoned decimal items. Each digit of a number is represented by a single byte. The 4 high-order bits of each byte are zone bits; the 4 high-order bits of the low-order byte represent the sign of the item. If the number is positive, these four bits contain a hexadecimal F. If the number is negative, these four bits contain a hexadecimal D. The 4 low-order bits of each byte contain the value of the digit.
The maximum length of an external decimal item is 18 digits.
+-------------------------------IBM Extension--------------------------------+
The maximum length of an external decimal item is 63 digits.
+----------------------------End of IBM Extension----------------------------+
+-------------------------------IBM Extension--------------------------------+
An external floating point item is a character string which has the following format:
+----------------------------End of IBM Extension----------------------------+
Figure 12 shows the internal representation of numeric items as specified by the USAGE clause. Numeric DISPLAY items include external decimal and external floating point data items. The computational numeric items are also shown in this figure: binary, internal decimal, and internal floating point data items.
Figure 12. Internal Representation of Numeric Items

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