Control Statement Format

The IAM control statements consist of 80-character logical records. The general format of these records is as follows:

General control statement format

Command Field

The command field identifies the control statement and consists of a one or more character command word. It may appear anywhere within columns 1 to 71 and can only be preceded by blanks. The command word must appear in its entirety within columns 1 to 71; it may not be continued.

Operand Field

The operand field, if present, follows the command field and is separated from it by at least one blank. The operand field consists of one or more keywords and/or positional parameters, separated by commas. It may not contain embedded blanks except within quoted strings. Operand fields may be continued onto subsequent logical records. If operands are to be used with a command, at least one operand must be on the logical record containing the command.

Comments Field

The comments field, if present, follows the operand fields and is separated by one or more blanks. It may contain any information deemed helpful by the person who codes the control statement. Comments fields may not be continued, that is, they must end at or before column 71. Comments are not permitted on a control statement that allows operands, but on which no operands have been specified.

Coding an Operand Field

An operand field consists of one or more positional or keyword parameters separated by commas.

Positional Parameters

Positional parameters must be coded in a specific order relative to one another. This means that the variable data you substitute for positional parameter 1 must precede the variable data for positional parameter 2. The absence of variable data to be substituted for a positional parameter is indicated by coding a comma in its place. However, you may omit the commas when the absent parameter is the last one, or if all following positional parameters are absent.

Keyword Parameters

Keyword parameters are position independent, and consist of either a keyword alone or a keyword followed by an equal sign (=) followed by user-specified variable information. When both positional and keyword parameters are to be coded in an operand, keyword parameters must precede positional parameters.

Sub-parameters

Both positional and keyword parameters may consist of a list of sub-parameters. Such a list is composed of positional parameters that follow the usual rules for that type. A sub-parameter list must be enclosed within parentheses, unless the list reduces to a single sub-parameter, in which case the parentheses may be omitted.

Quoted Strings

When the variable data you specify for a parameter contains certain special characters (defined below), you must enclose the data with apostrophes. This is called a 'quoted string'. Within a quoted string, all characters, including blanks, may appear; if an apostrophe is to be part of the string, it must be coded as two apostrophes.

Continuing an Operand Field

When the total length of an operand field exceeds the available columns in a logical record, it must be continued onto one or more following logical records. To continue an operand, interrupt the operand field after a complete parameter or sub-parameter, including the following comma. Do this at or before column 71. Leave the next column blank.

Continue the operand field starting anywhere between columns 1-71 on the following logical record.

Any number of logical record continuations may be present.

Example Continued Statement

Example of a continued control statement

Comment Statement

If you really have a lot to say, you may code a comment statement, which are control statements with nothing but remarks contained within columns 2 to 71. Comment statements are identified by an asterisk (*) in column 1. They may appear anywhere within a group of control statements, even between continued logical records.