FORTRAN

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FORTRAN
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The History of Fortran

• Before Fortran there was a dark computing abyss
• Assembly was the only prominent language
• Mostly due to extreme memory limitations

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continued

• 1954-57 an IBM team led by John Backus
• Nothing new
• Extremely efficient optimizing compiler

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continued

• The compiler was the key
• The scientific and military communities adopted
  Fortran as a standard
• Fortran required less skill to program in
• Programs could be developed in much less time
• NASA used Fortran extensively

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Fortran II

• 1958
• separate compilation of modules
• Assembly modules could be link-loaded by
  Fortran modules

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Fortran III

• Never released to the public
• Assembly could be injected right in the middle of
  Fortran code
• Lost HLL advantages when this happened

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Fortran IV

• 1961
• Cleaned up Fortran II
• Eliminated machine-dependent irregularities

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Fortran 66

• 1962-66 ASA standardized Fortran
• First HLL standard in the world

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More Fortran

• Fortran 77 improved on 66
• 1978 Disaster
• Fortran was caught up in political entanglements
  (Fortran Saga)
• 1991 gave Fortran 90
• Competition had caught up by this time
• Fortran 95 added minor improvements

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Understanding Fortran 77

• Constants
• Strings denoted with
• Not
• Integers are 1, 2, 3
• Real numbers are -123.4, (0.6x10-3), 7E-3
• Variable types
• 1-6 Characters per variable
• All uppercase
• All begin with an Alphabetic letter

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Understanding Fortran 77

• Variable Typing
• INTEGER, CHARACTER, REAL
• Ex. INTEGER AGE, AGE5
• Ex. CHARACTER NAME
• READ Statement
• Data input
• Ex. READ , NAME, AGE
• PRINT Statement
• Print data on the screen
• Ex. PRINT , Hello , NAME
• Assignment Operator
• AGE5 AGE 5

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Understanding Fortran 77

• Arithmetic Operators
• Evaluation Order
• , /, - (highest to lowest)
• Spaces are ignored
• Ex. -1.0/X Y/Z2
• ML cannot do this

Add
- Subtract
Multiply
/ Divide
Exponential
Expression Type Variable Type Rule
INTEGER REAL Convert to REAL
REAL INTEGER Truncate
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Understanding Fortran 77

• Program Example

Columns 1234567 - 72
C C Name and Age Program C PROGRAM EXPROG CHARACTER NAME INTEGER AGE, AGE5 C Input the name and age READ , NAME, AGE AGE5 AGE 5 PRINT , Hi , NAME, Your age is PRINT , AGE, and in 5 years your age will be PRINT , AGE5
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Understanding Fortran 77

• Programs
• Written in Columns
• Layout of punch cards
• Columns
• Comments
• Denoted by a C or a in the 1st column

1 5 6 7 72 73 - 80
Statement Labels Continued characters or blank FORTRAN Statements Unused
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Present Status

• The Array Language
• The abstract data type
• Requirements

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The Future

• Release Date
• Standards

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Quote

• Fortran is likely to remain into the next
  century as, at the very least, a special-purpose
  scientific and numerical language for
  large-scale, computing-intensive applications
  strengthen especially by its array capabilities,
  will be one of a small range of widely-used
  languages in general use.

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Source

• Michael Metcalf
• Paris, 1999 September