CS 325 Software Development and Systems www'bama'ua'edutruit002

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CS 325 Software Development and
Systemswww.bama.ua.edu/truit002
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Pre-class (just for fun)

• include ltiostream.hgt
• void main ()
• int count 0
• for (int x 0 xlt100 x5)
• if (x100)
• for (int y x yltx5 y)
• count
• cout ltlt count ltlt endl

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Lecture 4

• Today
• Functions and Arrays
• Project 1 Due Wed, 9/15/99 _at_midnight
• www.bama.ua.edu/truit002
• Will eventually be on cs.ua.edu/325
• Test 1 Tuesday, 9/14/99
• Chapters 1-4 from book
• Writing C code to solve problems
• Analyzing existing C code (no use of computers)
• Misc. questions
• Next Thursday Practice Session 1

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So far

• Sequence
• Selection
• if
• switch (later)
• Loops
• for
• while
• do (later)

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Modules in C

• Goals in software engineering Reusability,
  Maintenance, etc.
• C breaks code into classes and functions
• Well talk about classes and their methods after
  1st test
• Today, we learn to write functions in C

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Function definition syntax

• return_type functionId (param_list)
• function_body
• Return_type type of return value
• C convention name functions with verbNoun
  (i.e. averageGrades), however, any valid
  identifier will be valid
• Param_list list of arguments separated by
  commas
• Function body any valid declarations and
  statements that fulfill the purpose of the
  function

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Function Call Syntax

• functionId(actual_param_list)
• Pass by value
• Function gets a copy of the value passed
• Pass by reference
• Function gets the location of the value passed,
  therefore, function has right to change the
  contents at that location

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Function Prototype

• If the function is defined after main(), there
  must be a way for the compiler to recognize a
  call to that function within the body of the main
  program function prototype
• return_type functionID(type_for_each_parameter)
• This is unnecessary if the function is defined
  before main()

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Simple Example

• include ltiostream.hgt
• int getMin (int,int )
• void main()
• int num,temp, min
• cout ltlt How many grades do you want to enter?
  ltlt endl
• cin gtgt num
• cout ltlt enter the first number ltlt endl
• cin gtgt min
• for (int x 0 x lt num-1 x)
• cin gtgt temp
• mingetMin(min,temp)
• cout ltlt setw(7) ltltmin ltlt endl
• // end of main function

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Simple example contd

• int getMin(int num1, int num2)
• if (num1 gt num2)
• return num2 // new min
• else
• return num1

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Class Exercises

• Type this code in and run it (or cut and paste)
• Write another function that will find the maximum
  value

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Arrays

• List of common elements
• In most situations, we would want to keep grades.
  In our example, we simply discarded the grade
  after we compared it. We need to maintain the
  variables in a list, or an array

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Arrays in C

• element_type idarray_size
• Array notes
• All subscripts begin at 0.
• If array_size is 100, the range for the array is
  0..99.
• Access an array by idindex
• Each element may be treated as a variable

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Initialization options

• int exsize 0 //all elements set to 0
• int ex5 1,2,3,4,5 // position 0 set to 1,
  Position 1 set to 2, so on
• int ex 1,2 //will set array size to 2 with
  range 0..1
• int exsize
• Use for loop to initialize

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Simple Example

• include ltiostream.hgt
• void main()
• const int maxSize30
• int num, gradesmaxSize
• cout ltlt how many grades do you wish to enter?
  ltlt endl
• cin gtgt num
• for (int position 0 position lt num
  position)
• cout ltlt enter a grade ltlt endl
• cin gtgt gradesposition

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Class Exercises

• Type (cut and paste) program and try it
• Write the following functions
• findMin(array, numEl) ? min
• findMax(array, numEl) ? max
• findAvg(array, numEl) ? avg

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Operator Overloading

• Allows us to have two functions with the same
  name that take in different types of values

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One more class exercise

• Using same program, take the code out of the main
  program and write a function called getGrades to
  get the grades from the user
• Now write another getGrades, only do so with an
  array of doubles.

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End of Lecture 4

• Project 1 due Wed, 9/15/99 _at_ midnight
• www.bama.ua.edu/truit002
• Will eventually be on cs.ua.edu/325
• Test 1 Tuesday, 9/14/99