The four kinds of I/O are: formatted, unformatted, list-directed, and NAMELIST.
The two modes of access to files are sequential and direct. When you open a file, the access mode is set to either sequential or direct. If you do not set it explicitly, you get sequential by default.
The two types of files are: external files and internal files. An external file resides on a physical peripheral device, such as disk or tape. An internal file is a location in main memory, is of character type, and is either a variable, substring, array, array element, or a field of a structured record.