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[page 19]
ALPHABETIC AND ALPHAMERIC LITERALS
- An alphabetic or alphameric literal may contain any of the characters from the basic character set except the quotation mark. A blank is treated as a character and may be included in an alphameric literal.
- Like numeric literals, alphabetic and alphameric literals are limited to 50 characters in length and may not be carried over from one line to another when written on the columnar form used for writing procedure statements.
- All non-numeric literals must be enclosed in quotation marks to distinguish them from names. This rule applies even should the literal contain symbols (such as the arithmetic symbols and the blank) which may not be used in names.
Named Constants
Named constants are placed in the system by specifying them in the data description in accordance with the rules given in Chapter 4. Each named constant will usually have its own individual name, but in certain cases it may be part of a group of constants having a group name. As the reader will note from the discussion of tables and lists, individual items in a list are often in this category. However, even when the individual item does not have a name, it is always referred to by a name of some kind, and it may thus be treated in the general category of named constants.
A named constant may be referred to in procedure statements by writing its name as if it were any other data-name (although, of course, it should not be used in a way which will change its value).
Rules for Forming Named Constants
Named constants, like literals, may be wholly numeric, wholly alphabetic, or alphameric. All of the rules specified above for forming literals apply to constants, except as follows:
- Named constants are not limited as to length, and when written on the columnar form used for data description entries, they may be carried over from one line to the next. In this case they are subdivided and written as a series of complete constants, one on each line, but at a level lower than that of the name given to the total constant. After these parts have been read into the system, the processor will reassemble them to form the original constant.
- All named constants, including those which are wholly numeric, must be enclosed in quotation marks.
- Named constants may include any of the characters in the machine's character set, including the quotation mark and the blank. (The presence of a blank in an otherwise numeric constant makes it alphameric.)
Figurative Constants
The figurative constants resemble named constants except that their names are already assigned in the processor itself, so that the programmer need not write data description entries for them.
Figurative constants are names for certain constant quantities which are used frequently in data processing programs. The list includes names which represent zeros, blanks, and the lowest and highest characters in the collating sequence of the machine system being used. Following is a list of the figurative constants:
ZERO or ZEROS
BLANK or BLANKS
LOW.VALUE or LOW.VALUES
HIGH.VALUE or HIGH.VALUES
In general, a figurative constant is used to place the value it names in a given storage area, although it is not limited to this usage.