2. What is Fortran?

Fortran is a general purpose programming language, mainly intended for mathematical computations in, e.g., physics. Fortran is an acronym for FORmula TRANslation, and was originally capitalized as FORTRAN. However, following the current trend to only capitalize the first letter in acronyms, we will call it Fortran. Fortran was the first ever high-level programming language. The work on Fortran started in the 1950's at IBM and there have been many versions since. By convention, a Fortran version is denoted by the last two digits of the year the standard was proposed. Thus we have The most common Fortran version today is still Fortran 77, although Fortran 90 is growing in popularity. Fortran 95 is a revised version of Fortran 90 which (as of early 1996) is expected to be approved by ANSI soon. There are also several versions of Fortran aimed at parallel computers. The most important one is High Performance Fortran (HPF), which is a de-facto standard.

Users should be aware that most Fortran 77 compilers allow a superset of Fortran 77, i.e. they allow non-standard extensions. In this tutorial we will emphasize standard ANSI Fortran 77.

Why learn Fortran?

Fortran is the dominant programming language used in scientific and engineering applications. It is therefore important for physicists to be able to read and modify Fortran code. From time to time, so-called experts predict that Fortran will rapidly fade in popularity and soon become extinct. These predictions have always failed. Fortran is the most enduring computer programming language in history. One of the main reasons Fortran has survived and will survive is software inertia. Once a company has spent many man-years and perhaps millions of dollars on a software product, it is unlikely to try to translate the software to a different language. Reliable software translation is a very difficult task.

Portability

A major advantage Fortran has is that it is standardized by ANSI and ISO (see footnotes). Consequently, if your program is written in ANSI Fortran 77, using nothing outside the standard, then it will run on any computer that has a Fortran 77 compiler. Thus, Fortran programs are portable across machine platforms. (If you want to read some Fortran Standards Documents, click here.)
Footnotes:
ANSI = American National Standards Institute
ISO = International Standards Organization
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