C# Basics & MathThanachat Thanomkulabut
Outline2
Review Data Types Variable and Constant Declaration Arithmetic Expression Statement
Lecture 1: Program Structure
3
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
C# Beginning
namespace HelloW { class HelloWClass { static void Main () { System.Console.WriteLine("Hello World!"); System.Console.ReadLine(); } }}
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
4
Example
name Name
_data
9point
class class_A class_"A"
point9
C# Beginning
Outline5
Review Data Types Variable and Constant Declaration Arithmetic Expression Statement
6
What is in a 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); }
C# Beginning
What is Variable?A variable is used to store some
“data.”“It must be declared before it can be used”
Variable & Constant
7
Data TypesType Size Description Rangebool 1
byteStore truth value true / false
char 1 byte
Store one character
character code 0 – 255
byte 1 byte
Store positive integer
0 – 255
short 2 byte
Store integer -32,768 -- 32,767
int 4 byte
Store integer -2.1 x 109 -- 2.1 x 109
long 8 byte
Store integer -9.2 x 1018 -- 9.2 x 1018
double
16 byte
Store real number ± 5.0x10-324 -- ± 1.7x10308
string N/A Store sequence of characters
N/A
Variable & Constant
8
Outline9
Review Data Types Variable and Constant Declaration Arithmetic Expression Statement
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;
Variable & Constant
10
Multiple-Variable Declaration
11
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;
Variable & Constant
Test : Variable Declaration12
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’;
Variable & Constant
Test : Multiple-Variable Declaration
13
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;
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’;
Variable & Constant
14
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;
Variable & Constant
15
Test : Constant Declaration16
Declare Constant Name : e Type : double Initial value :
2.71828const double
e=2.71828;
Outline17
Review Data Types Variable and Constant Declaration Arithmetic Expression Statement
C# Expression18
Expression
Arithmetic
Expression
Boolean Express
ion
Expression
Arithmetic ExpressionOperators
+ - * / % (modulo: remainder after division)
Integer operates Integer IntegerInteger/Real operates Real/Integer RealExample
11 + 5 39 / 5 39.0/5 39 % 5 5.0 % 2.2
Arithmetic
167
40.6
19
7.8
Example20
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 = 2e = 0f = 2.5g = 2.5
Answer
Arithmetic
Pre/Post Increment & Decrement
Operator Meaning example
++x pre increment int a = 5;int b = ++a; // a, b = 6
x++ post increment int a = 5;int b = a++; // a = 6, b = 5
--x pre 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: Increment/decremente the value first, then use the
value Post in/de-crement:
Use the value first, then increment/decrement the value
In/Decrement
21
Pre & Post Increment22
Post:int a=5;int b=a++;Console.WriteLine(“a={0}, b={1}”,a,b);
a b5 56 a=6, b=5
Monitor
Pre:int a=5;int b=++a;Console.WriteLine(“a={0}, b={1}”,a,b);
a b5 66 a=6, b=6
Monitor
In/Decrement
Priority of Arithmetic Operators
Priority
Operator
1 Parentheses ()
2 x++, x--3 ++x, --x4 *, / , %5 +, -6 If equal priority, work from left
to right
23
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
a = -2b = 1c = 9
Answer
24
Arithmetic
Comparison
x/y*b++
25
2
Given x = 3.0, y = 2.0, b =2, what is the output?
x/y*++b3
Answer: 4.5 Answer: 3.0
Modify-and-Assign Operations
Statement Descriptionvar += expression Increment var by the value of expressionvar -= expression Decrement var by the value of expressionvar *= expression Multiply var by the value of expression,
then store the result in varvar /= expression Divide var by the value of expression,
then store the result in var
sum += x; // is equivalent to sum = sum + xprod *= 2.5; // is equivalent to prod = prod * 2.5y -= 3+a; // is equivalent to y = y – (3+a)
Modify-And-Assign
26
Example
sum += x; // is equivalent to sum = sum + xprod *= 2.5; // is equivalent to prod = prod * 2.5y -= 3+a; // is equivalent to y = y – (3+a)
Console.WriteLine(sum);Console.WriteLine(prod);Console.WriteLine(y);
Modify-And-Assign
27
double x = 1, sum = 2, prod = 3;int y = 4, a = 5;
37.5-4
Monitor
Math ClassMethod/Constant Value returned Example Call Result
PI Value of π Math.PI 3.1415927
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) 2.302585
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
Math Class
28
Example 29
What is the output?Console.WriteLine(Math.Round(3.499));
Console.WriteLine(Math.Floor(3.499));
Console.WriteLine(Math.Ceiling(3.499));
334
Monitor
Example 30
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))
5 3
Outline31
Review Data Types Variable and Constant Declaration Arithmetic Expression Statement
Statement A statement is a command to
computer class Hello { static void Main () { Console.WriteLine("Hello World!"); Console.ReadLine(); }}
Statement#1
Statement#2
Statement
32
C# Statement Types33
C# Statemen
t Types
Assignment
Statement
Input Statemen
t
Output Statemen
t
Statement
Assignment Statement To assign value to variable
Use equal sign (=) Syntax:
<variable> = <expression>;
int Width,Height;Width=10;Height=20+Width;
Statement
34
Output Statement Value
Math expression
More usages of output statement will be shown later in this course
Console.WriteLine(a);Console.WriteLine(a+b);Console.WriteLine(Math.Pow(a,b));
Console.WriteLine("Hello");Console.WriteLine(2012);
Statement
35
Any question?