Further Reading: I/O and Formatted Output

Fortran I/O is broad, and this chapter taught the working subset. When you need the exact rule for a descriptor, an access mode, or a namelist edge case, these are where to look. Sources are tagged Tier 1 (confident, recommended) and Tier 2 (real and worth seeking; confirm the current edition/URL yourself).

The reference you will reach for first

• Appendix F — I/O and Format Reference (this book). The full edit-descriptor catalog (g, en, d, l, b/o/z, scale factors), the format reversion rules, and a table of open/inquire specifiers. Keep it beside you while you write I/O. Tier 1.

The canonical books

• Stephen Chapman, Fortran for Scientists and Engineers (McGraw-Hill). Its formatted-I/O and file-processing chapters are thorough and example-driven, at exactly this book's level; the best place to see more worked format strings. Tier 1.
• Metcalf, Reid, and Cohen, Modern Fortran Explained (Oxford University Press). The definitive account of the I/O statements and the edit descriptors, including the parts we deferred — non-advancing I/O, asynchronous transfer, and the precise semantics of list-directed and namelist I/O. The book to settle an argument about what the standard actually says. Tier 1.
• Milan Curcic, Modern Fortran (Manning). Practical, modern-style I/O in the context of real programs, with good coverage of reading and writing data files the way working code does. Tier 1.

Free and online

• The GCC / gfortran documentation. The "GNU Fortran" manual documents how this compiler treats the processor-defined corners you must not guess about: the units of recl, the default rounding of formatted output, newunit behavior, and the exact form of list-directed and namelist output. When output does not match your hand computation, check here first. Tier 1.
• fortran-lang.org — Learn. The community tutorials include clear, current introductions to formatted I/O and file handling in modern style. Tier 1.
• The ISO/IEC 1539-1 Fortran standard (2018). Clause 12 (I/O) and Clause 13 (formatting) are the authoritative source. Dense, but definitive when a subtle question about records, connection modes, or edit descriptors has to be answered exactly. Tier 2 (specific clause numbers vary by edition — verify).

Where this chapter points next

• Unidata NetCDF and The HDF Group's HDF5 user guides. The self-describing, portable formats that solve the "raw binary is not self-describing" problem of §7.5 — the subject of Chapter 25. Skim their "what problem does this solve" introductions now; you will use them in earnest in Part VI. Tier 1.
• The VTK file-format documentation (Kitware). How to write simulation output that ParaView and VisIt can visualize, built directly on the formatted and binary I/O of this chapter — see Chapter 26. Tier 2.

Suggested order

1. Bookmark Appendix F and the gfortran manual now — between them they answer almost every "what exactly does this print?" question.
2. Read Chapman's I/O chapters alongside this one for more worked examples, especially of file processing.
3. When a format or access mode surprises you, check gfortran's processor-specific behavior before assuming a bug — most I/O surprises are documented, defined choices, not errors.
4. Reach for Metcalf/Reid/Cohen when you need the precise standard semantics — non-advancing I/O and the full namelist rules especially.
5. Skim the NetCDF/HDF5 introductions to see where scientific I/O is headed once text and raw binary stop scaling.