C# Basic Concept Thanachat Thanomkulabut

Naming Rules  Letters, digits and underscores(_)  First character  letter or _  Up to 63 characters long  Must not be a reserved word  Case Sensitive C# Language Overview 2 Example nameName _data 9point  class  class_A class_”A”  point9

Outline 3  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

C# Beginning 4  The starting point of the program is:  This is known as the method Main  A method is put inside a class  A class may be put inside a namespace static void Main () {... starting point... } static void Main () {... starting point... } C# Beginning

Main Method declaration 5  There are 4 ways to define Main function.  We use the simplest one.  static void Main() {...}  static void Main(string[] args) {...}  static int Main() {...}  static int Main(string[] args) {...} C# Beginning

6 Inside method Main  Variable declarations  Statements static void Main(string[] args) { const double pi = ; int radius; double area; radius = int.Parse(Console.ReadLine()); area = pi*radius*radius; Console.WriteLine(area); } C# Beginning

Outline 7  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

What is Variable? A variable is used to store “data.” “It must be declared before used” Variable & Constant 8

Data Types TypeSizeDescriptionRange bool1 byteStore truth valuetrue / false char1 byteStore one charactercharacter code 0 – 255 byte1 byteStore positive integer0 – 255 short2 byteStore integer-32, ,767 int4 byteStore integer-2.1 x x 10 9 long8 byteStore integer-9.2 x x double16 byte Store real number± 5.0x ± 1.7x stringN/AStore sequence of characters N/A Variable & Constant 9

C# Variable Declaration  Syntax: ;  Example:  We can also assign its initial value. Example: int radius; double area; bool isokay; int k = 200; bool done = false; Variable & Constant 10

C# Variable Declaration 11  Syntax:,,..., ;  Example:  We can also assign its initial value. Example: int width, length, height; double mean, sd, max, min; bool isokay, isright, check; int width=5, length=2, height=4;

Test I - Variable Declaration 12  Declare variable1  Name : num_Student  Type : interger  Initial value : nothing  Declare variable2  Name : gender  Type : character  Initial value : m  Declare variable3,4,5  Name3 : u  Name4 : t Name5 : a  Type : double  Initial value3 : 5.0  Initial value4 : nothing  Initial value5 : 9.8

C# Constant Declaration  Syntax: const = ;  Example: const int radius = 15; const double area=1.5; const bool isokay=true; const string movie=”StarWarIII”; const char mckazine=‘m’; Variable & Constant 13

C# Constant Declaration  Syntax: const =, =,..., = ;  Example: const int radius = 15, height = 5; const double area=1.5, wide=3.2, lenght = 4.1; Variable & Constant 14

Test II - Constant Declaration 15  Declare Constant  Name : e  Type : double  Initial value :

Outline 16  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

C# Expression 17 Expression Arithmetic Expression Boolean Expression Expression

Arithmetic Expression  Operators  + - * /  % (remainder after division)  Example    39 / 5   39.0/5   39 % 5   5.0 % 2.2  Expression

Piority of Arithmetic Operators Priorityoperator 1Parentheses () 2*, /, % 3+, - 4If equal precedence, left to right int a, b; a = 2-10*3/5+(6%4); b = 5*(15%4+(2-3))/9; a = -2 b = 1 Answer 19 Expression

Calculation Priority 20 static void Main(){ int a,b,c,d; double e,f,g; a=2; b=7; c=5; d=c/a; e=5/b; f=5.0/2; g=5/2.0; } d = 2 e = 0 f = 2.5 g = 2.5 Answer Expression

Boolean Expression  Operators  Comparison == Equal == != Not equal != < Less < > Greater > <= Less than or equal to <= >= Greater than or equal to >=  Boolean && And && || Or || ! Not ! 0 and 0 = 0 0 and 1 = 0 1 and 0 = 0 1 and 1 = 1 0 or 0 = 0 0 or 1 = 1 1 or 0 = 1 1 or 1 = 1 not 0 = 1 not 1 = 0 Expression 21

Example: Boolean Expression  10 > 50   ’A’ < ’B’  false true Expression 22

Outline 23  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

Statements  A statement is a unit of command to instruct your program  A method consists of one or more statements class Hello { static void Main () { Console.WriteLine("Hello World!"); Console.ReadLine(); } class Hello { static void Main () { Console.WriteLine("Hello World!"); Console.ReadLine(); } Statement#1 Statement#2 Statement 24

C# Statement Types 25 C# Statement Types Assignment Statement Input Statement Output Statement Statement

Assignment Statement  Assigning value to variable equal sign (=)  Use the equal sign (=) when making assignments.  Syntax: = ; = ; int Width,High; Width=10;High=20+Width; Statement 26

Input Statement  Console.ReadLine()  Return string  Use to get the input from user  Convert string to other data type  int.Parse() Convert string to integer  double.Parse() Convert string to double Example string st; st = Console.ReadLine(); Statement 27

Example: Input Statement Ex1: string myname; myname = Console.ReadLine(); Ex2: int Width; string temp1; temp1 = Console.ReadLine(); Width = int.Parse(temp1); Statement 28

Output Statements  Use the method Write or WriteLine in the Console class (which is in System namespace)  Basic usage:  Advanced usage:  Even more advanced usage: Console.WriteLine(”Size {0}x{1}”, width, height); double salary=12000; Console.WriteLine("My salary is {0:f2}.", salary); Console.WriteLine("Hello");Console.WriteLine(area); Statement 29

Outline 30  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

Increment & Decrement OperatorMeaningexample ++xpre increment int a = 5; int b = ++a; // a, b = 6 x++post increment int a = 5; int b = a++; // a = 6, b = 5 --xpre decrement int a = 5; int b = --a; // a, b = 4 x--post decrement int a = 5; int b = a- - ; // a = 4, b = 5  Pre in/de-crement:  Use the value which has already been in/de-crement.  Post in/de-crement:  Use the value before in/de-crement Modify-And-Assign 31

Increment & Decrement 32 Ex1: int a=5; int b=a++; Console.WriteLine(“a={0}, b={1}”,a,b); ab 556 a=6, b=5 Monitor Ex2: int a=5; int b=++a; Console.WriteLine(“a={0}, b={1}”,a,b); ab 566 a=6, b=6 Monitor

Modify-And-Assign Operations StatementDescription var += expression Increment var by the value of expression var -= expression Decrement var by the value of expression var *= expression Multiply var by the value of expression, then store the result in var var /= expression Divide var by the value of expression, then store the result in var sum += x; // is equivalent to sum = sum + x prod *= 2.5; // is equivalent to prod = prod * 2.5 y -= 3+a; // is equivalent to y = y – (3+a) int y=8; int a=2; Console.WriteLine(y -= 3+a); Try this ! Modify-And-Assign 33

Outline 34  C# Beginning  Variable and Constant  Expression  Statement  Modify-And-Assign  Math Class

The Math Class Method/ Constant Value returnedExample CallResult PI Value of  Math.PI Max(x,y)Larger of the twoMath.Max(1,2)2 Abs(x)Absolute value of xMath.Abs(-1.3)1.3 Sqrt(x)Square-root of xMath.Sqrt(4.0)2.0 Round(x)Nearest integer to xMath.Round(0.8)1 Pow(x,y)xyxy Math.Pow(3,2)9.0 Log(x)Natural log of xMath.Log(10) Ceiling(x)Smallest integer greater than or equal to x Math.Ceiling(4.1)5 Cos(x)Cosine of x radiansMath.Cos(Math.PI) Math Class 35

Test III 36  Write the program which  Input : Your name  Output : Your name is.

Test IV 37  Write the program which  Input : 3 number  Output : average of 3 input number

Test VI 38  Write the program which  Input : lenght of radius of circle  Output : Area of circle

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