SEN-442_Lecture01_BasicCSharpConstructs

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SEN-442
VISUAL PROGRAMMING
LECTURER:
Khawaja Mohiuddin
Computer Sciences Department
Bahria University (Karachi Campus)
[email protected]
https://sites.google.com/site/khawajamcs
Course Assessment
2
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Labs+Assignments+Project …………20%
Quizzes…………………………...…10%
Midterm…………………………..…20%
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Final Examination......................………. 50%
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Important Announcements
3
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Attendance
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Plagiarism
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Taking words, ideas, figures or materials from other sources and
presenting them as one's own
Students found guilty of plagiarism and academic dishonesty will be
subject to disciplinary action
Website (https://sites.google.com/site/khawajamcs)
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Mandatory for student to have at least 75% attendance
Otherwise, they will not be allowed to sit in the final examination
Visit website regularly for lectures, announcements and other material
Email Address ([email protected]u.pk)
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Send email only to Bahria email address
4
Basic C# Programming Constructs
Objectives
5
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Simple I/O Programs
Data Types in C#
Operators and Expressions
Control Structures
Arrays
Simple I/O Programs
6
ReadLine() method reads the next line of characters from the standard
input stream.
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WriteLine() method writes the specified data, followed by the current line
terminator, to the standard output stream.
using System;
public class Example {
public static void Main() {
string line;
Console.WriteLine("Enter one or more lines of text (press CTRL+Z to exit):");
Console.WriteLine();
do {
Console.Write(" ");
line = Console.ReadLine();
if (line != null)
Console.WriteLine(" " + line);
} while (line != null); } }
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Simple I/O Programs (contd.)
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using System; // System namespace contains class Console
public class Example { // class declaration
public static void Main() { // main method declaration
string line; // variable declaration of type string
Console.WriteLine("Enter one or more lines of text (press CTRL+Z to exit):");
// prints the specified text with line terminator
Console.WriteLine(); // prints empty line on the console
do { // start of do-while loop
Console.Write(" "); // prints one blank character without line terminator
line = Console.ReadLine(); // reads line of characters and stores in a variable
if (line != null) // if empty line was not entered
Console.WriteLine(" " + line); // prints blank character, line that was read and
line terminator
} while (line != null); // ends do-while loop only when line in null
Data Types in C#
8
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C# defines an intrinsic set of fundamental data types
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C# data type keywords are shorthand notations for full-blown types in the
System namespace.
Data Types in C# (contd.)
9
Operators
10
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In C#, an operator is a term or a symbol that takes one or
more expressions, or operands, as input and returns a
value.
Operators that take one operand, such as the increment
operator ( ++), are referred to as unary operators.
Operators that take two operands, such as arithmetic
operators ( +, -, *, /) are referred to as binary operators.
One operator, the conditional operator ( ?:), takes three
operands and is the sole tertiary operator in C#.
Operators (contd.)
11
Operators (contd.)
12
Operators (contd.)
13
Operators (contd.)
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Expressions
15
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Sequence of one or more operands and zero or more operators that can
be evaluated to a single value, object, method, or namespace.
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Can consist of a literal value, a method invocation, an operator and its
operands, or a simple name. Simple names can be the name of a variable,
type member, method parameter, namespace or type.
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Can use operators that in turn use other expressions as parameters, or
method calls whose parameters are in turn other method calls, so
expressions can range from simple to very complex.
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Examples of expressions:
1.
((x < 10) && ( x > 5)) || ((x > 20) && (x < 25))
2.
System.Convert.ToInt32("35")
Statements
16
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The actions that a program takes are expressed in statements.
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A statement can consist of a single line of code that ends in a semicolon,
or a series of single-line statements in a block.
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A statement block is enclosed in {} brackets and can contain nested blocks.
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Examples:
declaring variables, assigning values, calling methods, looping through
collections, and branching to one or another block of code, depending on
a given condition
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The order in which statements are executed in a program is called the flow
of control or flow of execution. The flow of control may vary every time
that a program is run, depending on how the program reacts to input that
it receives at run time.
Control Structures
17
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Specifies what has to be done by the program, when and under which
circumstances.
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Selection Control Structure specifies alternate courses of program flow,
creating a junction in your program.
Examples: single-selection structure (if), the double-selection structure
(if...else), the multiple-selection structure (switch), the inline conditional
operator (?:)
if (x > 10)
if (y > 20)
Console.Write("Statement_1");
else
Console.Write("Statement_2");
y > 20 ? Console.Write("Statement_1") : Console.Write("Statement_2");
Control Structures (contd.)
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int n = 2;
switch(n)
{
case 1:
case 2:
case 3:
Console.WriteLine("It's 1, 2, or 3.");
break;
default:
Console.WriteLine("Not sure what it is.");
break;
}
Control Structures (contd.)
19
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Repetition Control Structure specifies the repetition of an action while
some condition remains true.
Examples: do, for, foreach, in, while
do
{
Console.WriteLine(x);
x++;
} while (x < 5);
while (n < 6)
{
Console.WriteLine("Current value of n is {0}", n);
n++;
}
Control Structures (contd.)
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for (int i = 1; i <= 5; i++)
{
Console.WriteLine(i);
}
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Foreach-in statement repeats a group of embedded statements for each
element in an array or an object collection
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Can not be used to add or remove items from the source collection. If you
need to add or remove items from the source collection, use a for loop.
int[] fibarray = new int[] { 0, 1, 2, 3, 5, 8, 13 };
foreach (int i in fibarray)
{
System.Console.WriteLine(i);
}
Arrays
21
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An array is a data structure that contains several variables of the same
type
Can be Single-Dimensional, Multidimensional or Jagged.
A jagged array is an array of arrays, and therefore its elements are
reference types and are initialized to null.
The default value of numeric array elements are set to zero, and
reference elements are set to null.
Arrays are zero indexed: an array with n elements is indexed from 0 to
n-1.
Array elements can be of any type, including an Array type.
Array types are reference types derived from the abstract base type
Array.
foreach iteration can be used on all arrays in C#.
Arrays (contd.)
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class TestArraysClass {
static void Main() {
int[] array1 = new int[5]; // Declare a single-dimensional array
int[] array2 = new int[] { 1, 3, 5, 7, 9 }; // Declare and set array element values
int[] array3 = { 1, 2, 3, 4, 5, 6 }; // Alternative syntax
int[,] multiDimensionalArray1 = new int[2, 3]; // Declare a two dimensional array
// Declare and set array element values
int[,] multiDimensionalArray2 = { { 1, 2, 3 }, { 4, 5, 6 } };
// Declare a jagged array
int[][] jaggedArray = new int[6][];
// Set the values of the first array in the jagged array structure
jaggedArray[0] = new int[4] { 1, 2, 3, 4 };
}
}
Arrays (contd.)
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class ArrayClass2D {
static void Print2DArray(int[,] arr) {
// Display the array elements.
for (int i = 0; i < arr.GetLength(0); i++) {
for (int j = 0; j < arr.GetLength(1); j++) {
System.Console.WriteLine("Element({0},{1})={2}", i, j, arr[i, j]);
} } }
/* Output:
static void Main() {
Element(0,0)=1
// Pass the array as an argument.
Element(0,1)=2
Print2DArray(new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } });
Element(1,0)=3
Element(1,1)=4
// Keep the console window open in debug mode.
Element(2,0)=5
System.Console.WriteLine("Press any key to exit.");
Element(2,1)=6
System.Console.ReadKey();
Element(3,0)=7
} }
Element(3,1)=8
*/
Arrays (contd.)
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In C#, arrays are actually objects, you can use the properties, and other class
members, that Array has.
Arrays can be passed as arguments to method parameters. Because arrays
are reference types, the method can change the value of the elements.
Like all ref parameters, a ref parameter of an array type must be definitely
assigned by the caller. Therefore, there is no need to be definitely assigned
by the callee.
(The ref keyword causes arguments to be passed by reference. The effect is
that any changes to the parameter in the method will be reflected in that
variable when control passes back to the calling method.)
Like all out parameters, an out parameter of an array type must be assigned
before it is used; that is, it must be assigned by the callee.
(The out keyword causes arguments to be passed by reference. This is like
the ref keyword, except that ref requires that the variable be initialized
before it is passed.)
Conclusion
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In this Lecture, we…
 Learned about basic I/O operations in C#
 Identified the data Types provided by C#
 Learned about the different types of operators available in C#
 Looked at expressions and statements of C#
 Looked at the different types of Control Structures of C#
 Learned how arrays are used in C#
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