ICS 101 Introduction to Computer Programming LAB 8

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ICS 101 Introduction toComputer ProgrammingLAB
8

• Karim Asif Sattar
• karim_at_ccse.kfupm.edu.sa
• Information Computer Science Department King
  Fahd University of Petroleum Minerals

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Lab 8

• Reminder Quiz 4 will be next week
• Repetition
• Do Loop
• While Loop
• Do Loop
• Example
• Exercises

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Repetition

• Why is it needed?
• Repetition is done in FORTRAN using
• DO construct
• WHILE construct
• Single execution of the loop iteration
• The loop must terminate after finite number of
  iterations
• Each loop has termination condition

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Repetition

• Number of iterations is determined before loop
  begins execution
• The termination condition checks the number of
  iterations
• WHILE loop has different termination condition
• We will see that later

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DO Loop

• General form
• DO N index initial, limit, increment
• BLOCK OF STATEMENTS
• N CONTINUE
• Increment field is optional, default value will
  imply

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Do Loop (Contd)

• Example
• INTEGER K
• DO 15 K 1, 5, 2
• PRINT, K
• 15 CONTINUE
• END
• This will print 1, 3 and 5

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Example

• Consider this program
• REAL X1, X2, X3, X4, X5, X6
• REAL SUM, AVG
• READ, X1
• READ, X2
• READ, X3
• READ, X4
• READ, X5
• READ, X6
• SUM X1 X2 X3 X4 X5 X6
• AVG SUM / 6.0
• PRINT, AVG
• END

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Example (Cont)

• Using DO loop
• REAL X
• REAL SUM, AVG
• SUM 0
• DO 12 K 1, 6, 1
• READ, X
• SUM SUM X
• 12 CONTINUE
• AVG SUM / 6.0
• PRINT, AVG
• END

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DO Loop Rules

• Index must be of REAL or INTEGER type
• Increment value can be positive or negative but
  not zero
• It is possible to have DO loop without CONTINUE
  statement
• Default value of increment is 1 or 1.0
• DO loop can be executed once, many times, or zero
  time
• Loop parameters are evaluated before loop
  execution begins

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Nested DO Loops

• DO Loops can be nested
• Inner loop must start after outer loop and must
  finish before it
• You can have as many nested loops as needed

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Exercises(1)

• Write an integer FORTRAN function FACT that
  calculates the factorial of integer number
• FACT(0) 1
• FACT(1) 1
• FACT(n) n FACT(n-1)
• Use that function in FORTRAN program to calculate
  the factorial of number given by the user

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Exercise(2)

• Write a FORTRAN function SUMODD that calculates
  the summation of all odd numbers less than or
  equal N
• Use that function in FORTRAN program. Ask the
  user for the value of N