FORTRAN is the language of the past, and one of the languages of the present. It has gone through many stages since its creation in 1954.  Below we will discuss the reoccurring changes brought on by the continued upgrades of FORTRAN. The two most common versions of FORTRAN are FORTRAN IV and FORTRAN 77.

FORTRAN (~ 1954)

The first version of FORTRAN included an IF statement whose Boolean expression used relational operators in their algebraic form.  The major aspects of FORTRAN really begin to take form in the later versions.

FORTRAN I (1956)

FORTRAN I included an IF selection and the DO loop statement.  The 1956 version also included I/O formatting, variable names equal to or less than six characters and user-defined subroutines.  The new design was due to the IBM’s 704’s limited character set, causing the IF selection statement to be defined as an arithmetic selection.  FORTRAN 1 did not allow data typing statements.  Type and storage for all compilers was fixed before run time. This eliminated the possibility for recursive subprograms.  FORTRAN 1 is still used today.

FORTRAN II (1958)

FORTRAN II added remarkable improvements to the language.  Fortran II added the ability to separate compilations of subroutines and program modules.  Assembly language modules could also be ‘linked’ with FORTRAN modules.  These allowed changes to be made in the program without requiring the entire program to be recompiled.

FORTRAN III (1958)

FORTRAN III was never released to the public, it made it possible to use assembly language code right in the middle of FORTRAN code.  Using assembly code can be more efficient, but the advantages of a high level language were lost.

FORTRAN IV (1960/61)

FORTRAN IV was a ‘clean up’ of FORTRAN II.  It included important additions in explicit data type declaration, the logical IF construct, and the capability of passing subprograms as parameters to other subprograms. FORTRAN IV also improved the implementation of the COMMON and EQUIVALENCE statements, and eliminated some machine dependant language irregularities.

FORTRAN 66 (May 1962)

American Standards Association started developing standards for the FORTRAN language.  This made FORTRAN an even more popular high-level language. The new standard was published in 1966 and was known as FORTRAN 66.  This was the first high-level language standard in the world.

FORTRAN 77 (1978)

FORTRAN 77 added character handling, before characters were always stored inside integer variables.  The new Fortran 77 also added DO loops with a decreasing control variable, block if statements IF, THEN, ELSE, ENDIF, pretest of DO loops, Apostrophe delimited character string constants, and main program termination without a STOP statement.  Many compilers still use FORTRAN 77 standards today.

FORTRAN 90 (1992)  

This is the latest version of FORTRAN and is certainly different from FORTRAN 77. Fortran 90 adds many powerful extensions to FORTRAN 77. Like FORTRAN 70, FORTRAN 90 had many additions. Some of those additions were: free format of source code form; modern control structures; records; array notation; dynamic memory allocation; keyword argument passing; numeric precision in range control, and modules.  Recursive subprograms were also allowed. FORTRAN 90 gave FORTRAN the ability to compete against new high level languages like C.

FORTRAN 95

Still being developed.

Conclusion:

FORTRAN, as a high-level language, changed the ways computers were used.