The link tag (:link.) allows you to link to a heading, a footnote, an external database, or another application. The reftype= attribute is required with each link tag description. This attribute identifies the type of link you are defining.
The res= attribute and the value specified identify the window you are linking to. This attribute is the window identifier. A res= number must be in the range 1 through 64 000. The same window identifier must be specified in the tagging of the window you are linking to in order for a hypertext link to exist (see Hypertext Links).
The IPF compiler recognizes links to headings (including hidden headings) only when the heading level is within the default range (toc=123) or specified range of heading levels. If you specify a window identifier for a level that is lower in the hierarchy than that recognized for contents entries, and then attempt to link to it, the compiler returns an error message. For example, suppose the default is in effect for contents entries; that is, only heading levels 1 through 3 cause entries in the Contents window. Also suppose your file contains the following heading definition:
:h4 res=050.Copy File
The heading "Copy File" appears in the same window as the preceding heading level 3. If you use this window identifier in a link definition to link to the heading from another window, the IPF compiler returns the error message, No res for this reference.
If you are creating windows for an online document (a .INF file), you can use the res=, id=, or name= attribute of the heading tag to specify window identifiers. An advantage of using either id= or name= is that you can specify both alphabetic and numeric characters, which can make the job of assigning and remembering window IDs easier. If you use one of these attributes, you must use the refid= attribute of :link. when defining a hypertext cross-reference to the window.
If you need to use both res= numbers and id= values, you can specify both in a window heading. For simplicity, you can assign the same number to both identifiers.
Note: If an OS/2 application needs to communicate with an IPF window, you must use the res= attribute as a window identifier.