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[02.05.04]
C. Quantity Field
An entry in this field is used by the compiler to reserve storage for sequential data of the same format. If no value is specified, 1 is assumed. No check against this value is made at execute time. The maximum Quantity which may be specified is 2¹⁵ - 1. Since Quantity numbers are used to specify sequences of data descriptions for use of lists and tables, and since data in tables is referred to by the use of subscripted names, quantity numbers should not be assigned to data items not having names, unless these items include named items at a lower level.
D. Mode and Justify Fields
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The MODE column of the data description coding form merits careful attention. Internal mode (I) designates that the associated numeric field is to contain data in binary form. External mode (E) designates that the stored form is BCD.
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A numeric internal mode field designated as right justified (R) appears by itself in the low order positions of a full word (two if double precision) with the sign value in the sign bit of the word. Numeric external fields to be involved in extensive computation should be converted to this internal right justified by a preliminary SET or MOVE in order to prevent repetitive unpacking and converting.
The length of a numeric internal mode fixed point field designated as left justified or without justification specification is the least multiple of 6 bits sufficient to contain the number and its sign (leftmost bit of the field so designated). Left justification (L), as with external fields, reserves storage beginning with the leftmost bit of a new word and extending through as many words and bits as necessary. The no justification mode (blank) differs only in that storage reservation begins immediately to the right (within the same word if possible) of the preceding storage reservation.
For a right justified external mode field, storage is reserved beginning in a new word so that the field's last character is also the rightmost character of its final word.
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Specification of right justification is effective only for data items with explicitly described formats. Left justification is always effective.
E. Description Field
1. Pictorials
a) Definition of Allowable Data Field Types
The chart on the following page defines the types of formats which data fields may assume. The determining characteristics, allowable format description characters and proper field contents are shown for the various field types.
b) The pictorial characters A and X are considered to be synonymous by the 7090 CT Compiler.