The undoubted success of Fortran as the predominant programming language in the field of scientific and numerical computing is due in part to the steady evolution of the language. Following the publication of the first two standards in 1966 and 1978, the technical committee responsible for their development, X3J3, has been working for a decade on a new standard suitable for use in the 1990s. This new standard, at present still in draft form, will contain the new features required for large-scale computing on modern supercomputers, but still retain all of the familiar features which have made the language so popular. A first draft of the standard was subject to periods of public comment both in the USA and internationally. As a result, a new draft of the standard has been prepared. This book is a description of this new language, for the moment called Fortran 8x. It is intended to provide potential users of the language with a comprehensive guide to all its features, so that they can prepare for its introduction. The authors are both members of X3J3 and have many years of experience in the use of Fortran. The book is intended for existing Fortran users and for all those involved in any aspect of scientific and numerical computing.