When a program is loaded, its name is obtained using system routine GETARG and ignoring any path component of the name. If environment variable ADAM_IFL is defined, it is assumed to specify a search path as a list of directory names separated by semi-colons. Each directory in turn is searched for a file with the same name as the program and with extension .ifc or, failing that, .ifl. If such a file is found, it is used as the Interface Module.
ADAM Interface Module Reference Manual