CS1001 Lecture 27

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CS1001 Lecture 27

• Final Examination Review

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From Before the Midterm

• Basic Program Elements
• Declaration of Variables
• Declaration of Parameters
• Initialization of Variables
• Logical Operators
• Selective Execution
• CASE Statements
• Repetitive Execution
• How to Prompt for an Input

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Basic Program Elements

• Every program must have
• PROGRAM ProgramName
• IMPLICIT NONE
• END PROGRAM ProgramName
• Declaration of Variables
• REAL rVar1, rVar2
• INTEGER iVar1, iVar2
• CHARACTER(LEN) cVar1, cVar2LEN
• LOGICAL bVar

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Declaration of Parameters

• REAL, PARAMETER rCONS 3.14159
• INTEGER, PARAMETER iCONS 5240
• Initialization of Variables
• rVar1 1.23
• iVar2 2240
• cVar3 Hello world
• bVar4 .TRUE.

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• Relational Operators
• /
• lt
• gt
• lt
• gt

.EQ. .NE. .LE. .GE. .LT. .GT.
Logical Operators .NOT. .AND. .OR. .EQV. .NEQV.
Negation Conjunction Disjunction Equivalence Non
equivalence
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Selective Execution

• Normal IF Structure
• Simple IF Structure
• Normal IF Structure
• IF (log_exp1 .AND. log_exp2) THEN
• statements to be performed
• ELSE IF (log_ex3 .OR. log_ex4) THEN
• statements to be performed
• ELSE
• statements to be performed
• END IF

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Simple IF Statement

• IF (logical_expression) stmt
• e.g.,
• IF (logical_expression) EXIT
• Used to get out of an infinite DO loop
• Equivalent to
• IF (logical_expression) THEN
• EXIT
• END IF

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CASE Constructs

• SELECT CASE (iItem)
• CASE (0)
• statements to perform if iItem lt 0
• CASE (1)
• statements to perform if iItem 1
• CASE (25)
• statements to perform if iItem is 2-5
• CASE (9)
• statements to perform if iItem gt 9
• CASE DEFAULT
• statements to perform for other values
• END SELECT

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Repetitive Execution

• Counter-controlled loops perform an operation a
  given number of times
• DO-EXIT or while or until loops perform an
  operation until a condition becomes true that
  causes the loop to end
• Counter-Controlled
• DO iLoop init_val, final_val, step_size
• statements to be performed
• END DO

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DO-EXIT (While) Loop

• DO
• statements to be performed
• IF (logical expression) EXIT
• statements to be performed
• END DO

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Prompting for Input

• PRINT , Enter an integer from 1 to 9
• READ , iInput
• PRINT , Enter a value 0.0 or greater
• READ , rInput
• PRINT , Enter Q to quit
• READ , cInput

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Stuff Since the Midterm

• More Basic Program Elements
• Subprograms - Subroutines, Functions
• Structures
• One-Dimension Arrays
• Implied DO Loops
• Multi-Dimension Arrays
• Formatted Output
• Text Processing
• Internal Files
• How to Create a File
• How to Read from a File

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More Basic Program Elements

• Programs containing subprograms must contain the
  following
• PROGRAM MyProgram
• CONTAINS
• subprograms go here (internal)
• END PROGRAM MyProgram
• subprograms go here (external)

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Internal Subroutines

• Invoked with a CALL Statement
• CALL MySubRoutine(iArg, rArg)
• Defined after CONTAINS statement
• SUBROUTINE MySubRoutine(iArg, rArg)
• INTEGER, INTENT(IN) iArg
• REAL, INTENT(OUT) rArg
• INTEGER iLocalVariable
• REAL rLocalVariable
• statements to be performed
• END SUBROUTINE MySubRoutine

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External Subroutines

• Invoked with a CALL Statement
• CALL MySubRoutine(iArg, rArg)
• Defined after END PROGRAM statement
• SUBROUTINE MySubRoutine(iArg, rArg)
• INTEGER, INTENT(IN) iArg
• REAL, INTENT(OUT) rArg
• INTEGER iLocalVariable
• REAL rLocalVariable
• statements to be performed
• END SUBROUTINE MySubRoutine

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Internal Functions

• Invoked with an equation or statement
• rValue rMyFunction(iValue)
• Defined after the CONTAINS statement
• FUNCTION rMyFunction(iValue)
• REAL rMyFunction
• INTEGER, INTENT(IN) iValue
• statements to be performed
• rMyFunction some value to return
• END FUNCTION rMyFunction

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External Functions

• Invoked with an equation or statement
• rValue rMyFunction(iValue)
• Declared as EXTERNAL
• REAL, EXTERNAL rMyFunction
• Defined after the END PROGRAM statement
• FUNCTION rMyFunction(iValue)
• REAL rMyFunction
• INTEGER, INTENT(IN) iValue
• statements to be performed
• rMyFunction some value to return
• END FUNCTION rMyFunction

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Structures (not in exam)

• Declare a structure
• TYPE sVariable
• REAL rVar1, rVar2
• INTEGER iVar1, iVar2
• END TYPE sVariable
• Declare an instance of the structure
• TYPE(sVariable) sInstance
• Reference the variables in it
• iItem sInstanceiVar1
• rPrice sInstancerVar2

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One-Dimension Array

• Declare and dimension
• INTEGER, DIMENSION(19) iVar1, iVar2
• REAL, DIMENSION(025) rVar1, rVar2
• Initialize whole array
• iVar1 0
• iVar2 (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /)
• rVar1 9.99
• rVar2 (/1.0, 1.1, 1.2, 1.3, , 1.25 /)
• Reference elements using subscript
• iVar(8) 25
• rVar(19) 17.49

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Multi-Dimension Array

• Declare and dimension
• INTEGER,DIMENSION(19,13) iVar1, iVar2
• REAL, DIMENSION(025,15) rVar1, rVar2
• Initialize whole array
• iVar1 0
• rVar1 9.99
• Reference elements using subscript
• iVar(8,2) 25
• rVar(19,5) 17.49

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Formatted Output

• PRINT 20, iVar, rVar, cVar
• 20 FORMAT(1X, I2.2, 5X, F8.3, T20, A)
• 1X, 5X - horizontal spaces
• I2.2 - Integer, width of 2, minimum 2 digits
• F8.3 - Real, width of 8 (including sign and
  decimal point), with 3 decimal places
• T20 - Tab to absolute column position - column 20
• A - Alphabetic string

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Creating a File

• The file is opened as a new file for writing
• OPEN(UNIT12, FILEinput.dat, NEW, WRITE)
• Formatted data is written to the file
• WRITE(12,40) iVar, rVar, cVar
• 40 FORMAT(1X, I5, F8.3, A25)
• The file is closed
• CLOSE(12)

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Reading from a File

• The file is opened as an old file for read
• OPEN(UNIT13, FILEinput.dat, OLD, READ)
• Formatted data is read from the file
• READ(13,40,IOSTATEOF) iVar, rVar, cVar
• 40 FORMAT(1X, I5, F8.3, A25)
• The file is closed
• CLOSE(13)

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Internal Files

• Used to convert character form to integer
• given cDate November 25,1997
• then cYear cDate(1417)
• and READ (UNIT cYear, FMT (I4)) iYear
• Assigns the integer value 1997 to integer
  variable iYear

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Text Processing

• Getting the length of a string
• Var LEN(String)
• Var LEN(Hello, my name is) gt 17
• Finding text within a string
• Found INDEX(String, Text)
• Found INDEX(IMAGINE, IN) gt 5

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Implied DO Loops

• Used to read data into an array
• READ (10, ) (iInArr(I), I1, iLastNum)
• Equivalent to
• DO I 1, iLastNum
• READ (10, ) iInArr(I)
• END DO