The text read off it
[page 28]
- The rules of punctuation and spacing do not apply within literals, which may contain any character except the quotation mark, or within constants defined in the data description, which may contain any character. Alphabetic and alphameric literals, and all named constants, must be enclosed in quotation marks. (See the rules governing literals and named constants, beginning on page 18.)
- Floating point numbers are written as numeric literals. (See the discussion of numeric literals, beginning on page 18, and also the rules for writing floating point numbers in the data description, on page 80.)
- Parentheses must be used to group together two or more terms which are to be acted on by a single arithmetic operator, in accordance with the rule that all operators act on the next named item, or the next parenthetical expression, following the operator.
- Subscripts must be enclosed in parentheses, and if more than one subscript is used within the same parentheses, they must be separated by single commas. (See the discussion of lists, tables, and subscripts beginning below.)
- Parentheses may be used wherever needed in arithmetic expressions and in compound conditional expressions for the sake of clarity; where ambiguity would result from their omission, they must be used.
- Division headers must begin with single asterisks.
- Punctuation and spacing associated with any particular verb will be found in the general format prescribed for the verb in Chapter 3.
- When it is necessary to carry over an item from one line to another on either the procedure description or data description forms, selection of the “break point” must follow the rules given for those forms. In general, it should also be understood that a blank is assumed to follow Column 72 of the procedure description form and Column 71 of the data description form.
- When a function is named as an operand in a procedure statement, the names of the data to be substituted for the parameters must be placed in double parentheses immediately following the function-name. These data-names must be separated by single commas. (See the discussion of functions beginning on page 32.)
Lists, Tables, and Subscripts
Just as a clerk may use a reference table to obtain data, the programmer can direct the program to look up data in a list or table stored within the data processing system. The programmer must therefore know how to place the table in storage initially and how to write instructions for locating data in it.
A list, or table, may be regarded as an ordered grouping of data. The actual data may be either fixed or variable, depending on the need. If it is fixed, it is usually entered into the system as a series of constants; if it is variable, it will be either placed in the system when the input records are read in or produced as a result of some operation performed within the system.
In either case, it is necessary to establish the format of the table in such a way that the system can locate individual items of data within it. Thus, placing a table in the system requires two steps: (1) establishing the structure and format of the table, and (2) making provisions to enter the required data in that structure. When this is done properly, the programmer may call for any item of data in the table as required.