FORTRAN 77

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FORTRAN 77

• Presented by
• Destry Diefenbach

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The Free Online Dictionary of Computing
(http//foldoc.doc.ic.ac.uk/) Fortrash ltabuse,
languagegt /for'trash/ Hackerism for the Fortran
language, referring to its primitive design,
gross and irregular syntax, limited control
constructs, and slippery, exception-filled
semantics. Jargon File (1994-10-26)
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• Algol is FORTRAN done right. -Bruce Knobe,
  1973
• Pascal is FORTRAN done right. -Raymond
  Langsford, 1980
• FORTRAN 77 is FORTRAN done right. -James Ball,
  1983

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History of FORTRAN

• Stands for IBM Mathematical FORmula TRANslation
  System but abbreviated to FORmula TRANslation
• FORTRAN 0 was developed by a IBM research team
  headed by John Backus in 1954.
• Was the first high-level programming language

John Backus 1924-1988
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More History

• The design of FORTRAN made it easier to translate
  mathematical formulas into code.
• FORTRAN originally began as a digital code
  interpreter for the IBM 701
• At that time it was called Speedcoding
• The point of FORTRAN was to make programming
  easier.

IBM 701
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FORTRAN I 1957

• Was the first compiler
• By 1958 over 50 of software was in FORTRAN
• Cut development time.
• 2 weeks to 2 hours

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FORTRAN II - IV

• FORTRAN II
• Independent compilation
• Fix the bugs
• FORTRAN III
• Was developed, but it was never widely distrbuted
• FORTRAN IV
• Explicit type declarations
• Logical selection (IF) statement
• Subprogram names could be parameters
• ANSI standard in 1966

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FORTRAN 77

• FORTRAN 77 replaced FORTRAN IV as the new
  standard.
• It retained most of the features of IV
• It added
• Character string handling
• Logical loop control statements
• And a If with a optional else statement

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Data Types

• FORTRAN 77 explicitly permits data types of
  integer, real, double precision, complex,
  logical, and characters.

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Real Data Types

• Represent decimal numbers
• It uses scientific notation
• 3E5 300000
• .123E-3 .000123

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Double Precision Data Types

• Instead of E it used D
• 1D2 100

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Complex Data Types

• Built in complex number data type
• Which occupies 2 bytes
• The first byte in the pair represents the real
  part of the complex data type.
• The second byte represents the imaginary part of
  the complex item.
• represented as follows
• Numeric Value
• (4.61,-6.81) 4.61 6.81i
• (-10,5) -105i

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Program Structure

• A FORTRAN program is a collection of subprogram
  definitions.
• Subprograms may be a FUNCTION that returns
  values, a SUBROUTINE that doesnt return a value,
  and one must be the main program

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Main Program

• The main program receives control of the
  processor when an executable program is loaded
  for execution.
• There can be only one main program in an
  executable program.
• That main program is identified by the fact that
  it does not have a FUNCTION, SUBROUTINE, or BLOCK
  DATA statement as its initial statement.

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Intrinsic Functions

• FORTRAN 77 has many intrinsic functions
• Examples
• SQRT( ) square root
• FLOAT( ),INT ( ) type conversions
• COS( ),SIN( ), TAN( ) trig functions

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Statement Functions

• Statement functions are one line defined
  functions that is internal to the program unit in
  which it is defined
• Example of a statement function
• ROOT(A,B,C) (-BSQRT(B2-4.0AC))/(2.0A)

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Subprograms

• The main abstraction devices in FORTRAN 77 are
  the subroutines and functions.
• The subroutine definition
• SUBROUTINE SWAP (I,J)
• M I
• I J
• J M
• RETURN
• END
• Functions are structurally similar to subroutines.

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Control Structures

• GOTO statements
• IF statements
• DO statement
• CONTINUE statement
• STOP and PAUSE statements
• END statement

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GOTO Statements

• The GOTO statement is used to direct program
  control to indicated by the statement number
  specified in the respective GOTO statement
• Three types of GOTO statements
• Unconditional GOTO 100
• Computed GOTO(1,2,3)I
• Assigned GOTO I,(1,2,3)

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IF Statements

• Contains IF, ELSE IF, ELSE, END IF
• Example
• IF(Q) THEN
• AB
• CD
• ELSE IF (R) THEN
• EF
• GH
• ELSE
• XY
• ZW
• END IF

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DO Statement

• The DO statement is used to establish a
  controlled loop
• Example DO
• DO 10 I 1,10,1

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CONTINUE,STOP PAUSE, and END STATEMENT

• The CONTINUE statement serves as a point of
  reference in a program
• No operational function is performed
• It is frequently used in DO loops to provide a
  terminal statement
• The STOP and PAUSE statements do a similar task
• The STOP terminates execution
• The PAUSE terminates execution, but leaves the
  program in a resumable state
• The END statement marks the physical end of a
  program

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EVALUATION

• Readability
• Writability
• Reliability
• Cost

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Readability

• FORTRAN 77 is not to hard to read on a small
  scale, but when many GOTO statements are involved
  it gets very difficult
• Identifiers can only be six characters long

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Writability

• Depends on what you are using it for.
• Is a pretty simply language

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Reliability

• Is not very reliable
• Only static type checking
• Lack of exception handling

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Cost

• Cheap
• Lots of free resources/compilers
• A fairly easy language to learn

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Bibliography

• Marshall, A C. A Brief History of FORTRAN 77. 8
  Sept. 1997 http//www.liv.ac.uk/HPC/HTM
  LF90Course/HTMLF90CourseNotesnode29.html
• ibiblio.org. A Brief History of FORTRAN. No date
  http//www.ibiblio.org/pub/languages/fortran/ch1-1
  .html
• American National Standards Institute, Inc.
  American National Standard Programming Language
  FORTRAN. April 3, 1978. http//www.fortran.com/F77
  _std/rjcnf-0.html
• Chivers, Ian D. Sleightholme, Jane. Interactive
  FORTRAN 77 A Hands on Approach 2nd ed. 1984.
  http//www.kcl.ac.uk/kis/support/cit//fortran/f77b
  ook.pdf
• William, Waite. FORTRAN 77 Semantic Analysis. No
  date. http//eli-project.sourceforge.net/fortran_h
  tml/Semantics.htmls1
• Bellis, Mary. Inventors of the Modern Computer.
  No date. http//inventors.about.com/library/weekly
  /aa072198.htm
• Page, Rex. Didday, Rich. Alpert, Elizabeth.
  FORTRAN 77 for Humans, 3rd ed. 1986 West
  Publishing Company
• Katzan, Harry Jr. FORTRAN 77, Computer Science
  Series. 1978 Van Nostrand Reinhold Company