HP OpenVMS Systems Documentation

HP COBOL
User Manual

HP COBOL allows comparison of both numeric class operands and nonnumeric class operands; however, it handles each class of data differently. For example, it allows a comparison of two numeric operands regardless of the formats specified in their respective USAGE clauses, but it requires that all other comparisons (including comparisons of any group items) be between operands with the same usage. It compares numeric class operands with respect to their algebraic values and nonnumeric (or numeric and nonnumeric) class operands with respect to a specified collating sequence. (See Section 2.5.1 for numeric comparisons.)

If only one of the operands is numeric, it must be an integer data item or an integer literal, and it must be DISPLAY usage. In these cases, the manner in which the compiler handles numeric operands depends on the nonnumeric operand, as follows:

• If the nonnumeric operand is an elementary item or a literal, the compiler treats the numeric operand as if it had been moved into an alphanumeric data item the same size as the numeric operand and then compared. This causes any operational sign, whether carried as a separate character or as an overpunched character, to be stripped from the numeric item so that it appears to be an unsigned quantity.
  In addition, if the PICTURE character-string of the numeric item contains trailing P characters, indicating that there are assumed integer positions that are not actually present, they are filled with zero digits. Thus, an item with a PICTURE character-string of S9999PPP is moved to a temporary location where it is described as 9999999. If its value is 432J (--4321), the value in the temporary location will be 4321000. The numeric digits take part in the comparison.
• If the nonnumeric operand is a group item, the compiler treats the numeric operand as if it had been moved into a group item the same size as the numeric operand and then compared. This is equivalent to a group move.
  The compiler ignores the description of the numeric item (except for length) and, therefore, includes in its length any operational sign, whether carried as a separate character or as an overpunched character. Overpunched characters are never ASCII numeric digits. They are characters ranging from A to R, left brace ({), or right brace (}). Thus, the sign and the digits, stored as ASCII bytes, take part in the comparison, and zeros are not supplied for P characters in the PICTURE character-string.

The compiler does not accept a comparison between a noninteger numeric operand and a nonnumeric operand. If you try to compare these two items, you receive a diagnostic message at compile time.

3.4.1.2 Comparison Operations

If the two operands are acceptable, the compiler compares them character by character. The compiler starts at the first byte and compares the corresponding bytes until it either encounters a pair of unequal bytes or reaches the last byte of the longer operand.

If the compiler encounters a pair of unequal characters, it considers their relative position in the collating sequence. The operand with the character that is positioned higher in the collating sequence is the greater operand.

If the operands have different lengths, the comparison proceeds as though the shorter operand were extended on the right by sufficient ASCII spaces (decimal 32) to make both operands the same length.

If all character pairs are equal, the operands are equal.

3.4.2 Class Tests for Nonnumeric Items

An IF statement with a class condition tests the value in a nonnumeric data item (USAGE DISPLAY only) to determine whether it contains numeric, alphabetic, or user-defined data and uses the result to alter the flow of control in the program. For example:

IF ITEM-1 IS NUMERIC...
IF ITEM-2 IS ALPHABETIC...
IF ITEM-3 IS NOT NUMERIC...

If the data item consists entirely of the ASCII characters 0 to 9, with or without the operational sign, the class condition is NUMERIC. If the item consists entirely of the ASCII characters A to Z (upper- or lowercase) and spaces, the class condition is ALPHABETIC.

The ALPHABETIC-LOWER test is true if the operand contains any combination of the lowercase alphabetic characters a to z, and the space. Otherwise the test is false.

The ALPHABETIC-UPPER test is true if the operand contains any combination of the uppercase alphabetical characters A to Z, and the space. Otherwise, the test is false.

You can also perform a class test on a data item that you define with the CLASS clause of the SPECIAL-NAMES paragraph.

A class test is true if the operand consists entirely of the characters listed in the definition of the CLASS-NAME in the SPECIAL-NAMES paragraph. Otherwise, the test is false.

When the reserved word NOT is present, the compiler considers it and the next key word as one class condition defining the class test to be executed. For example, NOT NUMERIC determines if an operand contains at least one nonnumeric character.

If the item being tested is described as a numeric data item, it can only be tested as NUMERIC or NOT NUMERIC. The NUMERIC test cannot examine either of the following:

• An item described as alphabetic
• A group item containing elementary items whose data descriptions indicate the presence of operational signs

For further information on using class conditions with numeric items, refer to the HP COBOL Reference Manual.

3.5 Data Movement

Three HP COBOL statements (MOVE, STRING, and UNSTRING) perform most of the data movement operations required by business-oriented programs. The MOVE statement simply moves data from one item to another. The STRING statement concatenates a series of sending items into a single receiving item. The UNSTRING statement disperses a single sending item into multiple receiving items. Section 3.6 describes the MOVE statement. Chapter 5 describes STRING and UNSTRING.

The MOVE statement handles most data movement operations on character strings. However, it is limited in its ability to handle multiple items. For example, it cannot, by itself, concatenate a series of sending items into a single receiving item or disperse a single sending item into several receiving items.

Two MOVE statements will, however, bring the contents of two items together into a third (receiving) item if the receiving item has been subdivided with subordinate elementary items that match the two sending items in size. If other items are to be concatenated into the third item, and they differ in size from the first two items, then the receiving item requires additional subdivisions (through redefinition).

Example 3-1 demonstrates item concatenation using two MOVE statements.

01  SEND-1        PIC X(5) VALUE "FIRST".
01  SEND-2        PIC X(6) VALUE "SECOND".
01  RECEIVE-GROUP.
    05  REC-1     PIC X(5).
    05  REC-2     PIC X(6).
PROCEDURE DIVISION.
A00-BEGIN.
    MOVE SEND-1 TO REC-1.
    MOVE SEND-2 TO REC-2.
    DISPLAY RECEIVE-GROUP.
    STOP RUN.

The result of the concatenation follows:

FIRSTSECOND

Two MOVE statements can also disperse the contents of one sending item to several receiving items. The first MOVE statement moves the leftmost end of the sending item to a receiving item; then the second MOVE statement moves the rightmost end of the sending item to another receiving item. (The second receiving item must first be described with the JUSTIFIED clause.) Characters from the middle of the sending item cannot easily be moved to any receiving item without extensive redefinitions of the sending item or a reference modification loop (as with concatenation).

The STRING and UNSTRING statements handle concatenation and dispersion more easily than compound moves. Reference modification handles substring operations more easily than compound moves, STRING, or UNSTRING.

3.6 Using the MOVE Statement

The MOVE statement moves the contents of one item into another. For example:

MOVE FIELD1 TO FIELD2

MOVE CORRESPONDING FIELD1 TO FIELD2

FIELD1 is the sending item name, and FIELD2 is the receiving item name.

The first statement causes the compiler to move the contents of FIELD1 into FIELD2. The two items need not be the same size, class, or usage; they can be either group or elementary items. If the two items are not the same length, the compiler aligns them on one end or the other. It also truncates or space-fills the other end. The movement of group items and nonnumeric elementary items is discussed in Section 3.6.1 and Section 3.6.2, respectively.

The MOVE statement alters the contents of every character position in the receiving item.