1. Thanachat Thanomkulabut
C# Basics & Math
Thanachat Thanomkulabut

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

3. Lecture 1: Program Structure
C# Beginning
Lecture 1: Program Structure
The starting point of the program is:
This is known as the Main method
A method is put inside a class
A class can be put inside a namespace
namespace HelloW {
class HelloWClass {
static void Main () {
System.Console.WriteLine("Hello World!");
System.Console.ReadLine(); }

4. Lecture 1: Variable Naming Rules
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
class_A
class_"A"

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

6. What is in a program? Variable declarations Statements
C# Beginning
What is in a program?
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); }

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

8. Data Types Type Size Description Range bool 1 byte Store truth value
Variable & Constant
Data Types
Type
Size
Description
Range
bool
1 byte
Store truth value
true / false
char
Store one character
character code 0 – 255
byte
Store positive integer
0 – 255
short
2 byte
Store integer
-32, ,767
int
4 byte
-2.1 x x 109
long
8 byte
-9.2 x x 1018
double
16 byte
Store real number
± 5.0x ± 1.7x10308
string
N/A
Store sequence of characters

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

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

11. Multiple-Variable Declaration
Variable & Constant
Multiple-Variable Declaration
Syntax:
<data type> <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. Test : Variable Declaration
Variable & Constant
Test : Variable Declaration
Declare variable1
Name : num_Student
Type : integer
Initial value : nothing
Declare variable2
Name : gender
Type : character
Initial value : m
int num_Student;
char gender = ‘m’;

13. Test : Multiple-Variable Declaration
Variable & Constant
Test : Multiple-Variable Declaration
Declare variables 1,2,3
Name1 : u
Name2 : t Name3 : a
Type : double
Initial value1 : 5.0
Initial value2 : nothing
Initial value3 : 9.8
double u=5.0, t, a=9.8;

14. Constant Declaration Syntax: Example:
Variable & Constant
Constant Declaration
Syntax:
const <data type> <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. Multiple-Constant Declaration
Variable & Constant
Multiple-Constant Declaration
Syntax:
const <data type> <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 :
const double e= ;

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

18. Arithmetic Expression
Boolean Expression

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

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

21. Pre/Post Increment & Decrement
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
Operator
Meaning
example
++x
pre increment
int a = 5;
int b = ++a; // a, b = 6
x++
post increment
int b = a++; // a = 6, b = 5
--x
pre decrement
int b = --a; // a, b = 4
x--
post decrement
int b = a- - ; // a = 4, b = 5

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

23. Priority of Arithmetic Operators1
Parentheses () 2
x++, x-- 3
++x, --x 4
*, / , % 5
+, - 6
If equal priority, work from left to right

24. Example int a, b, c; a = 2-10*3/5+(6%4); b = 5*(15%4+(2-3))/9;
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 x/y*b++ Answer: 4.5 Answer: 3.0
Given x = 3.0, y = 2.0, b =2, what is the output?
x/y*++b
x/y*b++ 3 2
Answer: 4.5
Answer: 3.0

26. Modify-and-Assign Operations
Statement
Description
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)

27. Example 3 7.5 -4 double x = 1, sum = 2, prod = 3; int y = 4, a = 5;
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 Method/ Constant Value returned Example Call
Result PI
Value of π
Math.PI
Max(x,y)
Larger of the two
Math.Max(1,2) 2
Abs(x)
Absolute value of x
Math.Abs(-1.3)
1.3
Sqrt(x)
Square-root of x
Math.Sqrt(4.0)
2.0
Round(x)
Nearest integer to x
Math.Round(0.8) 1
Pow(x,y) xy
Math.Pow(3,2)
9.0
Log(x)
Natural log of x = ln x
Math.Log(10)
Floor(x)
Greatest integer smaller than or equal to x
Math.Floor(4.9) 4
Ceiling(x)
Smallest integer greater than or equal to x
Math.Ceiling(4.1) 5
Cos(x)
Cosine of x radians
Math.Cos(Math.PI) -1

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

30. Example cos(π/3) | ln(4) |
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 A statement is a command to computer Statement#1
class Hello {
static void Main () {
Console.WriteLine("Hello World!");
Console.ReadLine(); }
Statement#2

33. C# Statement Types C# Statement Types Assignment Statement
Input Statement
Output Statement

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

35. Output Statement Value Math expression
More usages of output statement will be shown 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?