Lab Session-X CSIT121 Spring 2002

1
Lab Session-X CSIT121 Spring 2002

• Arrays and Their Usage
• Examples and Lab Exercises
• Passing Arrays to Functions
• Examples and Exercises
• Sorting an Array

2
Arrays and Their Usage

• Arrays consist of several data items that are of
  same data type and related to each other.
• An array associates one name to a group of
  related data items that belong to the same data
  type
• Example
• const int ARRSIZE5
• int studentsARRSIZE0
• cingtgtstudent_index
• if (student_index ltARRSIZE)
• cout ltltstudentsstudent_indexltltendl

3
Arrays and Their Usage

• One serious problem in array handling is the
  unintentional indexing outside the bounds of an
  array
• For example
• studentsARRSIZE2 32
• This problem may corrupt memory cells outside the
  array boundary

4
Lab Exercise 9-1

• Let us work on making a histogram of performance
  for students in a class.
• int gradesARRSIZE7,14,13,13,11,7,7,8,8,13,13,1
  4,14,7,14,8,14,11
• int frequency5
• (We have only 5 different scores reported)
• Record frequencies
• Plot histogram using sign

5
Passing Arrays to Functions

• Arrays are passed to functions as reference
  arguments
• Functions can modify arrays if programmer does
  not protect the arrays
• The way to protect is to add const keyword before
  the array name in declaration and definition of
  the function

6
Passing Arrays to Functions

• As an example, consider multiplying all the
  elements of an array with a value and storing the
  results in another array.
• We would like to protect the original array when
  we call this function
• int original54,7,12,31,24
• int multiplied50

7
Lab Exercise 9-2 (DEMO)

• Define a function that takes in two arrays of the
  same size and stores the reverse of the first
  array into the second array.
• Protect the first array with const identifier
• Check if protection works by trying to violate it
• Complete the program by displaying contents of
  original and reversed arrays

8
Sorting an Array

• Let us try to sort an array in ascending order
• The basic algorithm is as follows
• Find the smallest value in the array
• Bring this value to index 0
• Find the smallest value in the remaining array
• Bring this value to index 1

9
Sorting an Array

• Continue doing so until the remaining array
  consists of only one element
• Try implementing the algorithm
• Post Lab Exercise 9-3
• Test sorting with a test case as below
• Scores10 9,7,8,4,7,2,4,1,7,5

10
Practice Problems

• Declare a character array consisting of 10
  locations. Read any ten characters from the
  keyboard into the array and then print the whole
  array using coutltltarrayname
• Declare an integer array having 90 locations and
  initialize it with odd numbers in a counter
  controlled loop. For example, I0 1, I13,
  I25 I37 and so on