Chapter 16. MULTIPLE-LEVEL ARRAYS AND TABLES

CHAPTER OBJECTIVES

Upon completion of this chapter, you should be able to

  • Establish a series of items using a double-level OCCURS clause.

  • Demonstrate how to establish a series of items within a multiple-level array.

  • Demonstrate how to look up data stored in a multiple-level array.

  • Access and manipulate data defined with a triple-level (or more) OCCURS clause.

DOUBLE-LEVEL OCCURS CLAUSE

When describing an area of storage, as many as seven levels of OCCURS are permitted.

Like a single-level OCCURS, multiple levels of OCCURS may be used for (1) accumulating totals in an array, or (2) storing a table for "look-up" purposes. We will look first at multiple-level arrays and then at multiple-level tables.

DEFINING A DOUBLE-LEVEL, OR TWO-DIMENSIONAL, ARRAY

Suppose we wish to establish in storage an array of hourly temperature readings for Los Angeles or any other city during a given week. Once the array is established, it is used to perform various calculations. The array consists of 7 × 24 temperature readings; that is, there are 24 hourly temperature readings for each of 7 days. The array is represented as

DEFINING A DOUBLE-LEVEL, OR TWO-DIMENSIONAL, ARRAY

To define this array in WORKING-STORAGE with a single-level OCCURS would require the following coding.

DEFINING A DOUBLE-LEVEL, OR TWO-DIMENSIONAL, ARRAY

The ellipses, or dots (. . .), indicate that 24 elementary ...

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