Lecture06 computer applicationsie1_dratifshahzad

DR ATIF SHAHZAD
Computer Applications
in Industrial Engg.-I
IE-322
LECTURE #6

Computer Applications in
Industrial Engg.-I
IE322

…Recap
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What we will see…
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Introduction toArrays
Declaration & Definition
Initialization
Arrays in loops Foreach loop
AccessingArray Elements
Array Methods and
properties
Multidimensional arrays Passing by ref
Passing by value
Listbox with arrays
Random number arrays

Array
a data structure
used to store a collection of data.
a collection of variables of the same type.
Remember, an Array is areference type.
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Array use case
For example, consider a situation where
you need to store 100 numbers.
Rather than declare 100 different variables,
you can
just declare an array that stores
100 elements.
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Array Declaration
int[ ] myArray; // an array of integers
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Array Definition
int[ ] myArray = new int[5]; // an array
of integers that can hold 5 integers
Since arrays are objects, we need to
instantiate them with the new keyword
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Array Definition: Question
Fill in the blanks to instantiate an array of
42 elements of type double:
_____ [ ] a = ___ double[ __];
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Array Definition:Answer
Fill in the blanks to instantiate an array of
42 elements of type double:
double [ ] a = new double[ 42];
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Array Initialization
string[ ] names = new string[3] {"John",
"Mary", "Jessica"};//an array of strings
that can hold 3 strings and is initialized as
well
Note the use of [ ]and { }
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Array Initialization: Question
Fill in the blanks to instantiate the array
with initial values:
int[ ] a = _1, 2, 3_ ;
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Array Initialization:Answer
Fill in the blanks to instantiate the array
with initial values:
int[ ] a = {1, 2, 3} ;
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double[ ] prices = new double[4] {3.6,
9.8, 6.4, 5.9};// an array of doubles that
can hold 4 numbers and is initialized
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string[ ] names = new string[ ] {"John",
"Mary", "Jessica"};
double[ ] prices = new double[ ] {3.6, 9.8,
6.4, 5.9};
We canomit the size declaration when
the number of elements are provided in
the curly braces
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string[ ] names = {"John", "Mary",
"Jessica"};
double[ ] prices = {3.6, 9.8, 6.4, 5.9};
We can evenomit the new operator.
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string[] daysOfWeek =
{ "Monday", "Tuesday",
"Wednesday","Thursday", "Friday",
"Saturday", "Sunday" };
We can evenomit the new operator.
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Summarizing in code…
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Int32[] iArray1; //Declaration Only
iArray1 = new Int32[5];//Definition
Int32[] iArray2 = new Int32[5]; //Declaration and Definition
Int32[] iArray3 = new Int32[5] { 21, 22, 23, 24, 25 };//Declaration,
Definition & Initialization
Int32[] iArray4 = new Int32[] { 11,12,13,14,15}; //Declaration, Definit
ion & Initialization (can omit size value only if initialization)
Int32[] iArray5 = { 31,32,33,34,35};//Declaration, Definition & Initial
ization (can omit new keyword only if initialization)

Accessing Array Elements
What is the value of x after these
statements execute?
int[ ] a = {4, 7, 2};
int x = a[0]+a[2];
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Remember that
the first element
has index 0.

Each element of an array has an index
number.
int[ ] b = {11, 45, 62, 70, 88};
Console.WriteLine(b[2]);
//Outputs 62
//Outputs 70
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Remember that
the first element
has index 0.

Each element of an array has an index
number.
int[ ] b = {11, 45, 62, 70, 88};
//Outputs 62
//Outputs 70
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Remember that
the first element
has index 0.

Using loops with Arrays
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Int32[] iArray3 = new Int32[5] { 21, 22, 23, 24, 25 };//Declaration
, Definition & Initialization
for (Int32 i=1;i<5;i++)
{
Console.WriteLine(iArray3[i]);
}

Using foreach loops with Arrays
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Int32[] iArray3 = new Int32[5] { 21, 22, 23, 24, 25 };//Declaration
, Definition & Initialization
foreach (Int32 j in iArray3)
{
Console.WriteLine(j);
} always through all
elements – from
the start to the end
order of iteration
is consecutive

Multidimensional Arrays
Declaration and Definition of 2D array
Declaration and Definition of 3D array
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int[,] iArray55 = new int[5,5];
int[,,] iArray345 = new int[3, 4 , 5];

Declaration,Definition & Initialization of
2D array
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int[,] iArray23 = new int[3, 2] { { 1, 2 }, { 3, 4 }, { 5, 6 } };
int[,] iArray32 = new int[2, 3] { { 1, 2, 3 }, { 4, 5, 6 } };

Accessing elements of 2D array
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Console.WriteLine("Element in third row
and first column of iArray23:" + iArray2
3[2, 0]);

Multidimensional Arrays: Example
Printing a Matrix
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// Declare and initialize a matrix of size 2 x 4
int[,] matrix =
{
{1, 2, 3, 4}, // row 0 values
{5, 6, 7, 8}, // row 1 value
};
// Print the matrix on the console
for (int row = 0; row < matrix.GetLength(0); row++)
{
for (int col = 0; col < matrix.GetLength(1); col++)
{
Console.Write(matrix[row, col]);
}
Console.WriteLine();
}

Some Arrays Properties
Length
// Total number of elements in all dimensions
Rank
// Number of dimensions
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Arrays Properties
Console.WriteLine("Rank of iArray5 is:"
+ iArray5.Rank); // Dimensions
Console.WriteLine("Length of
iArray5 is:" + iArray5.Length);// size
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Some Arrays Methods
Min()
Max()
Sum()
Average()
GetLength(int dim)
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Arrays Methods
Console.WriteLine("Min of iArray5 is:" +
iArray5.Min());
Console.WriteLine("Max of
iArray5 is:" + iArray5.Max());
Console.WriteLine("Sum of
iArray5 is:" + iArray5.Sum());
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Question
What will be the output
int [ ] array={1, 2, 3, 4, 5};
int total=0;
for (int i=1; i<array.Length; i=i+2)
total=total+array[i];
Console.Write(total);
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Question
What will be the output
int [ , ] d = { { 1, 2, 1 }, { 1, 2, 1 }, {2, 0, 1} } ;
for ( int j= 1; j < d.GetLength(1); j++ )
{
int total=0;
for ( int i = 0; i< d.GetLength(0); i++ )
{
total=total + d[ i, j];
}
Console.WriteLine( "{0} ", total);
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Question
What is the error?
This code should sum up all the elements in the array x
int i = 1;
int [ ] x = { 2, 3, 4, 5 };
int total=0;
while (i < 4)
{
total += x[i];
i++;
}
Console.WriteLine(total);
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Question
Make a program to generate 500 random
numbers between 1 and 1000. Find
Minimum, maximum, Sum and Average of
these numbers using Array Methods.
Display these numbers in a listbox.
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Passing Arrays to Methods
Variables that store an
object (like an array) DO
NOT store the object
itself, rather just a
reference to the object
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Passing Arrays to Methods
So we have:
•ValueType variables
•ReferenceTypeVariables
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ValueType
• Some examples are int, char,
and float, which stores
numbers, alphabets, and
floating point numbers,
respectively.
• When you declare an int type,
the system allocates memory to
store the value.
The
value
types
directly
contain
data.
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ReferenceType
• In other words, they refer to a memory
location
• Example of built-in reference
typesafe: object, dynamic, and string.
• You can declare the reference parameters
using the ref keyword.
The reference
types do not
contain the
actual data
stored in a
variable, but
they contain a
reference to
the variables.
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Lecture06 computer applicationsie1_dratifshahzad

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42
NEVER hesitate to
contact should you
have any question
Dr.Atif Shahzad

Lecture06 computer applicationsie1_dratifshahzad

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