BIL106E

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BIL106E

• Basic FORTRAN

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Contents

• Data Types
• Names and Type Declarations
• Arithmetic Expressions and Assignment
• Simple Input/Output

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Data Types

• Five Basic Types of Fortran
• Integer
• Real
• Complex
• Character
• Logical
• Custom Data Types

Numerical Data Types
Non-Numerical Data Types
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Integer

• An Integer is a whole number (positive, negative,
  or zero) and does not contain commas or a decimal
  point.
• Examples
• 5
• 1024
• -512
• a5 b1024 c-512
• Integer variable declaration in F
• integer a,b,c

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Real

• A real number must contain a decimal point, but
  no commas are allowed.
• Examples
• 5.125
• -0.0273
• 0.0571
• 6.5274684E3 means 6.5274684X103
• x5.125 y-0.0273 z0.0571
• Real variable declaration in F
• real x,y,z

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Complex

• A complex number is represented as a pair of real
  (i.e., floating point) numbers.
• The first component of the pair represents the
  real part of the complex data object and the
  second represents the imaginary part.
• For example
• Z a i b Z (a,b)
• -34i
• NOTE Since you dont have enough background on
  complex numbers,
• you are not responsible from complex numbers and
  its related
• examples.

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Character

• Character constants, also called strings, are
  sequences of symbols from the ANSI standard
  character set for Fortran.
• The number of character constants between double
  quotes is the length of constant
• For example
• "This is a string" (the length is 16)
• "abcD-12o" (the length is 8)
• "John Q. Doe" (the length is 11)
• NOTE Use straight quotes " not smart quotes or
  
• character variable declaration in F
• Character (lenlenght) name1, name2
• Lenght positive int or positive int constant
  expression

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Allowed characters in F

• A B C D E F G H I J K L M N O P Q R S T U V W X Y
  Z
• a b c d e f g h i j k l m n o p q r s t u w x y z
• 0 1 2 3 4 5 6 7 8 9
• ? - / ( ) , . ' lt gt ! " ?
• where ? represents the space or blank character

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Logical

• An object of logical type has the value
• true or false, or (0 or 1), or (yes or no).
• in F syntax
• .TRUE.
• .FALSE.
• logical variable declaration in F
• logical flag1, flag2

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• Data Types
• Names and Type Declarations
• Arithmetic Expressions and Assignment
• Simple Input/Output

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Names

• Data objects are memory locations in which
  information is stored. There are 2 kind of basic
  data objects constants and variables.
• Constant's value can NOT change during the
  execution of the porgram. It remains constant.
• A variable's value CAN change during the
  execution of the porgram.
• Names show the location of the data objects in
  the computers memory.

Computer's memory
Name of the data object
year 2003
Address of memory location
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Names

• Examples for names
• Average, X, Y, Einstein, or Potential_Energy.
• "Name"s are any kind of word either
• - "reserved word"s ? can not be used by you,
• - "identifier"s ? defined by you
• IMPORTANT reserved words (keywords) such as
  program, write, and end are not actually names

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Syntax for Names

• Names in a program must conform to 3 rules
• 1) A name may contain up to 31 letters, digits,
  and underscore characters (which must not be the
  last character of the name)
• 2) The first character of a name must be a letter
• 3) Imbedded blank characters are not permitted in
  a name
• Examples
• Degree aVariable CONSTANT
• Name_Surname Var2 var_6_A
• this_not_valid_
• this is not_valid

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Type Declarations for Variables

• Every variable must appear in a type declaration
• The type of a Fortran variable determines the
  type of value that may be assigned to that
  variable.
• In every F program, the specification statement
  implicit none must immediately follow the program
  statement
• program Research
• implicit none
• ...
• end program Research
• Type Declaration Form
• Type List of names

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Type Declarations for Variables

• implicit none
• integer Counts, Loop_Index
• real Current, Resistance, Voltage
• character (len12) MyName, YourName
• Names defined as part of the F language,
  including keywords and intrinsic function names
  (such as sin, tan, abs, etc.), must be written in
  lower case.
• Names that you invent can use any combination of
  upper and lower case, but each name must be
  written consistently.

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Variable initialization

• All variables are initially undefined
• Initialization in the declarations
• Examplesreal W1.2, z5.678,
  mass4.56integer year1998, count0

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Constants

• Constant's value can NOT change during the
  execution of the porgram.
• 2003 is an integer constant
• 3.1415 is a real constant
• "Happy birty day to you" is a character constant
• It is not a good practice to use the same
  constant with its fixed value at different places
  of the code. When we need to change the value we
  have to search and replace for all the
  appearances of it within the program which is a
  tedious and an error-prone task.
• What should we do ?
• Use ? Named Constants

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Type Declaration for Named Constants

• Declaration of a named constant is as follows
• Type, parameter List of initializations
• where each item in the List of initializations
  has the form
• Name value
• The value definition is an explicit constant.
• Examples
• integer, parameter LENGTH12
• real, parameter PLANK6.6260755e-34,
  PI3.141593
• real, parameter GRAVITY9.807,
  AVAGADRO6.0221367e23,
• twoPI2.0PI
• integer, parameter A20, HIGH30, NEON67
• character (Len2), parameter unitsCm
• ATTENTION Continuation line with ampersand
  symbol.
• It's a good practice to write named constants in
  upper case

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• Data Types
• Names and Type Declarations
• Arithmetic Expressions and Assignment
• Simple Input/Output

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Arithmetic Expressions and Assignment

• Expression An expression consists of a
  combination of operators and operands
• Examples
• 4
• -6
• 421
• a(bc/d)/20
• q52
• xq3
• agt3

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Arithmetic Operators in F

• Operator Meaning
• addition
• - substraction
• multiplication
• / division
• exponentiation

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Priorities of Operators

• Operator Priority
• High (1st)
• and / Medium (2nd)
• and - Low (3rd)
• Examples
• A b c d / e f g / h I j k
• 2 3 2 512
• 10/5 2 2 2 4
• To calculate 51/3 5.0(1.0/3.0)
• but not
• 5.0(1/3) à 5.00 à 1.0

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Priority Rules

• All exponentiations are performed first
  consecutive exponentiations are performed from
  right to left
• All multiplications and divisions are performed
  next in the order in which they appear from left
  to right
• Additions and subtractions are performed last, in
  the order in which they appear from left to right

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Example

• 2 3 2 512
• 10/5 2 2 2 4
• (23)2 82 64
• 10/(52) 10 / 10 1
• To be at the safe side
• Use ? ( )

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Assignment Statement

• Formvariable expression
• Assigns the value of expression to variable
• Assignment is not a statement of algebraic
  equality
• it is a replacement statement
• ExamplesDensity 2000.0Volume 3.2Mass
  DensityVolumeWeightRatio log(Mass/90.)

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Mixed-mode assignment

• Assume that, b is a real variable whose value is
  100.0, while c and d are integers having the
  values 9 and 10, respectively.
• a bc/d
• result is 90.0
• a c/db
• a gets 0 value.
• This phenomenon is known as integer division

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Statement

• Statements are the primary building blocks of a
  program.
• Two kind simple and compound (block)
• Some Simple statements
• Declaration real aValue, x
• Assignment aValue 34 x
• Function call call aFunction(aValue)
• Control if (x 0) then
• 
  aValue 34
• end if
• Null ! explanation
• They are executed in sequence for their effect,
  and do NOT have values.

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• Data Types
• Names and Type Declarations
• Arithmetic Expressions and Assignment
• Simple Input/Output

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Simple Input/Output

• Two kinds of I/O (for the moment!)
• Formatted I/O
• List-directed I/O
• List-directed outputprint , output-listwrite
  (unit, fmt) output-list
• List-directed inputread , input-listread
  (unit, fmt) input-list

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Simple Input/Output

• An asterisk as the unit in a read or write
  controls list designates the default input device
  (the keyboard) or the default output device (the
  terminal screen)
• An asterisk as the format designates
  list-directed formatting. Input data values for
  on-line list-directed input are entered at the
  computer keyboard in free form. Values must be
  separated by blanks.
• For example
• read (unit , fmt ) xval,yval,zval
• can be entered as
• 10.0 100.0 2.5

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Simple Input/Output

• IMPORTANT The items in an input list must be
  variable names.
• Examples
• write (unit , fmt ) Please enter the
  diameter of a circle
• read (unit , fmt ) Diameter
• write (unit , fmt ) Diameter ,
  Diameter, circumference ,
• 3.1416Diameter, Area , 3.1416Diameter2
• print , "Tell me your birthday"
• write (unit, fmt) a, b, c2
• read , day, month, year

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Program style and design

• A program must be correct, readable, and
  understandable. The basic principles for
  developing a good program are as follows
• 1) Programs cannot be considered correct until
  they have been validated using test data.
• 2) Programs should be well structured
• Use a top-down approach when developing a program
  for a complex problem.
• Strive for simplicity and clarity
• 3) Each program unit should be documented
• Include opening documentation
• Use comments
• Use meaningful identifiers
• Label all output
• 4) A program should be formatted in a style that
  enhances its readability
• 5) Programs should be readable and understandable
• Do not use magic numbers
• Use comments to describe the purpose of a program
  and variables

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Example
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Example
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Example
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Example
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Example
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Example
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Warnings for Frequently Made Errors

• 1) Do NOT use TAB in the editor
• 2) Do NOT use single quatition mark for
  characters
• 3) Place , between successive variables in
  command like print , write, declerations etc

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Homework 1

• Every student will caluculate
• Perimeter and Area of Circle, Rectangle and
  Triangle
• USE named constant(s), Variables
• Input all necessary variable data from keyboard
  and print out all data and results.
• Run your program for three different data sets.
• Include both sourse code and program output in
  your work
• Use Courier New font for source code and output
• Due date 20/2/2003
• Homeworks will be delivered in a floppy disk

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Term Project

• Establish teams for TERM PROJECT consisting of 5
  student, choose a team representative. Each
  representative email me the members of the teams.
• Due Date 20/2/2003

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Self Study

• ELLIS PHLIPS book
• p. 55 Self-test Exercise 3.1
• Problem 9
• p. 63 Self-test Exercise 3.2
• Problem 4
• Reading Assignement
• p. 103-134