Programming Languages

History of Fortran

Development of Fortran

• in early computers, programs written using machine instructions encoded in bits

• simple tasks required many instructions

• programmer needed to know instruction code and other internal details

• frequent errors which were difficult to correct

• difficult to understand programs

• program for a machine unusable on another

Development of Fortran

• need was felt to simplify programming

• concentrate on the method for solving a problem rather than internal details

• make programs more readable and usable on more than one machine

• develop a language for describing a program

• develop a translator for converting a program in this language to the machine form

Development of Fortran

• Fortran was the first such language ( 1954)

• name derived from Mathematical Formula translation system

• meant mainly for numerical computation

• machine instructions replaced by statements

• syntax of statements precisely defined

• each statement can be translated into a sequence of machine instructions

Development of Fortran

• memory addresses replaced by variable names in statements

• translators did the job of assigning addresses to variables

• translators were themselves programs and were called compilers

• compilers were dependent on the machine but Fortran itself was machine independent

• many Fortran compilers were developed (60s)

Fortran Versions

• early Fortran allowed very simple statements

• meant only for numerical computation

• compiler developers added more powerful statements

• resulted in many versions of Fortran

• need for standardization

• first Fortran standard called Fortran 66

• specified allowed statements precisely

Fortran 77

• early Fortran proved very successful

• many complex programs developed which were widely used

• led to development of other programming languages with other types of statements

• need was felt for adding more features to Fortran to simplify programming further

• Fortran standard was revised and a new standard called Fortran 77 developed

Fortran 90

• Fortran 77 was enormously successful

• used for more than a decade for scientific and engineering applications

• many powerful Fortran codes were developed

• computer science grew as a discipline

• the power of the computer for non-numerical applications became apparent

• languages such as C, Pascal were developed to exploit this power

Fortran 90

• Fortran did not have some of the features supported by these new languages

• Fortran 77 proved inadequate for the non-numerical applications that grew very fast

• again, a need was felt for adding some of the new features to Fortran

• took almost a decade for the new Fortran standard, Fortran 90

• Fortran 90 is as powerful as C, Pascal

Why Fortran?

• oldest programming language

– led to development of other languages

– contains all basic programming concepts

• widely used for more than 40 years

– many well tested programs are available

– Fortran compilers are amongst the best

– machine code generated is optimized

– common errors are easily detected

Why Fortran?

• many built-in features for numerical computation

• Fortran 90 includes all the desirable features of newer languages like C and Pascal and other modern languages

• simplicity

– Fortran 90 syntax is easy to read

– easy to identify programming errors

Disadvantages of Fortran

• old language

– many of earlier features of Fortran have proved harmful in hindsight

– retained to ensure that old programs continue to work on new machines

– should not be used in new programs

• not suitable for “low level programming” like writing an OS

• does not support new programming styles

Summary

• Fortran is the oldest programming language

• developed to make programs easier to write, readable and portable

• Fortran hides internal machine details from programmer

• compilers translate a Fortran program into the form required by the machine

• many versions of Fortran

• Fortran 90 includes all desirable features