C# Basics & Math

1. C# Basics & Math Thanachat Thanomkulabut

2. Outline • Review • Data Types • Variable and Constant Declaration • Arithmetic Expression • Statement

3. C# Beginning Lecture 1: Program Structure • 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 namespace HelloW { class HelloWClass { static void Main () { System.Console.WriteLine("Hello World!"); System.Console.ReadLine(); } } }

4. C# Beginning Lecture 1: Variable Naming Rules • Letters, digits and underscores(_) • First character must be a letter or _ • Up to 63 characters long • Must not be a reserved word Example name Name point9 9point _data class_A class_"A" class

5. Outline • Review • Data Types • Variable and Constant Declaration • Arithmetic Expression • Statement

6. C# Beginning What is in the Program? • Variable declarations • Statements static void Main(string[] args) { const double pi = 3.1416; int radius; double area; radius = int.Parse(Console.ReadLine()); area = pi*radius*radius; Console.WriteLine(area); }

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

8. Variable & Constant Data Types

9. Outline • Review • Data Types • Variable and Constant Declaration • Arithmetic Expression • Statement

10. Variable & Constant Variable Declaration • Syntax: <datatype> <name>; • Example: • We can also assign its initial value. Example: int radius; double area; bool isokay; int k = 200; bool done = false;

11. Variable & Constant Multiple-Variable Declaration • Syntax: • <datatype> <name_1>, <name_2>,..., <name_n>; • Example: • We can also assign their initial value. Example: int width, length, height; double mean, sd, max, min; bool isokay, isright, check; int width=5, length=2, height=4;

12. Variable & Constant Test : Variable Declaration • Declare variable1 • Name : num_Student • Type : integer • Initial value : nothing • Declare variable2 • Name : gender • Type : character • Initial value : m intnum_Student; char gender = ‘m’;

13. Variable & Constant Test : Multiple-Variable Declaration • Declare variables 3,4,5 • Name3 : u • Name4 : t Name5 : a • Type : double • Initial value3 : 5.0 • Initial value4 : nothing • Initial value5 : 9.8 double u=5.0, t, a=9.8;

14. Variable & Constant Constant Declaration • Syntax: const <datatype> <name> = <value>; • Example: const int radius = 15; const double area=1.5; const bool is_done=true; const string movie=”StarWarIII”; const char my_initial=‘m’;

15. Variable & Constant Multiple-Constant Declaration • Syntax: const <datatype> <name_1> = <value_1>, <name_2> = <value_2>, ... , <name_n> = <value_n>; • Example: const int radius = 15, height = 5; const double area=1.5, width=3.2, length = 4.1;

16. Test : Constant Declaration • Declare Constant • Name : e • Type : double • Initial value : 2.71828 const double e=2.71828;

17. Outline • Review • Data Types • Variable and Constant Declaration • Arithmetic Expression • Statement

18. Expression C# Expression

19. Arithmetic Arithmetic Expression • Operators • + - * / • % (modulo: remainder after division) • Integer operates IntegerInteger • Integer/Real operates Real/Integer  Real • Example • 11 + 5  • 39 / 5  • 39.0/5  • 39 % 5  • 5.0 % 2.2  16 7 7.8 4 0.6

20. Arithmetic Example static void Main(){ int a,b,c,d; doublee,f,g; a=2; b=7; c=5; d=c/a; e=5/b; f=5.0/2; g=5/2.0; } Answer d = 2 e = 0 f = 2.5 g = 2.5

21. In/Decrement Pre/Post Increment & Decrement • Pre in/de-crement: • Increment/decremente the value first, then use the value • Post in/de-crement: • Use the value first, then increment/decrement the value

22. In/Decrement Pre & Post Increment a b Monitor Post: int a=5; int b=a++; Console.WriteLine(“a={0}, b={1}”,a,b); 5 6 5 a=6, b=5 a b Monitor Pre: int a=5; int b=++a; Console.WriteLine(“a={0}, b={1}”,a,b); 5 6 6 a=6, b=6

23. Arithmetic Priority of Arithmetic Operators

24. Arithmetic Example • int a, b, c; • a = 2-10*3/5+(6%4); • b = 5*(15%4+(2-3))/9; • c = 5+9%2*4-14/4%3 Answer a = -2 b = 1 c = 9

25. Comparison • x/y*b++ Given x = 3.0, y = 2.0, b =2, what is the output? • x/y*++b 2 3 • Answer: 4.5 • Answer: 3.0

26. Modify-And-Assign Modify-and-Assign Operations 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)

27. Modify-And-Assign Example double x = 1, sum = 2, prod = 3; int y = 4, a = 5; 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) Console.WriteLine(sum); Console.WriteLine(prod); Console.WriteLine(y); Monitor 3 7.5 -4

28. Math Class Math Class

29. Example • What is the output? Monitor 3 3 4 Console.WriteLine(Math.Round(3.499)); Console.WriteLine(Math.Floor(3.499)); Console.WriteLine(Math.Ceiling(3.499));

30. Example • Write arithmetic expressions using Math class • cos(π/3) • | ln(4) | Math.Cos(Math.PI/3) Math.Pow(3,0.2) Math.Abs(Math.Log(4))

31. Outline • Review • Data Types • Variable and Constant Declaration • Arithmetic Expression • Statement

32. Statement Statement • A statement is a command to computer Statement#1 class Hello { static void Main () { Console.WriteLine("Hello World!"); Console.ReadLine(); } } Statement#2

33. Statement C# Statement Types

34. Statement Assignment Statement • To assign value to variable • Use equal sign (=) • Syntax: <variable> = <expression>; intWidth,Height; Width=10; Height=20+Width;

35. Statement Output Statement • Value • Math expression • More usages of output statement will be showed later in this course Console.WriteLine("Hello"); Console.WriteLine(2012); Console.WriteLine(a); Console.WriteLine(a+b); Console.WriteLine(Math.Pow(a,b));

36. Any question?