The I/O control list specifies one or more of the following:
This specifier must be present; the rest are optional.
No control specifier can appear more than once, and the list must not contain both a format specifier and namelist group name specifier.
Control specifiers can take any of the following forms:
When the keyword form (for example, UNIT=io-unit) is used for all control-list specifiers in an I/O statement, the specifiers can appear in any order.
When the nonkeyword form (for example, io-unit) is used for all control-list specifiers in an I/O statement, the io-unit specifier must be the first item in the control list. If a format specifier or namelist group name specifier is used, it must immediately follow the io-unit specifier.
When a mix of keyword and nonkeyword forms is used for control-list specifiers in an I/O statement, the nonkeyword values must appear first. Once a keyword form of a specifier is used, all specifiers to the right must also be keyword forms.
The following sections describe the control-list specifiers in detail.