C Basics Math Thanachat Thanomkulabut Outline 2 Review

C# Basics & Math Thanachat Thanomkulabut

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

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

C# Beginning 4 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 _data class point 9 class_A 9 point class_"A"

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

C# Beginning What is in a program? 6 Variable declarations Statements static void Main(string[] args) { const double pi = 3. 1416; int radius; double area; radius = int. Parse(Console. Read. Line()); area = pi*radius; Console. Write. Line(area); }

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

Variable & Constant Data Types 8 Type Size Description bool 1 byte Store truth value true / false char 1 byte Store one 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. 0 x 10 -324 -± 1. 7 x 10308 string Store sequence of characters N/A Range

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

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

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

Variable & Constant Test : Variable Declaration 12 Declare variable 1 Declare variable 2 Name : num_Student Type : integer Initial value : nothing Name : gender Type : character Initial value : m int num_Student; char gender = ‘m’;

Test : Multiple-Variable Declaration 13 Variable & Constant Declare variables 1, 2, 3 � Name 1 : u Name 2 : t Name 3 : a � Type : double � Initial value 1 : 5. 0 Initial value 2 : nothing Initial value 3 : 9. 8 double u=5. 0, t, a=9. 8;

Variable & Constant Declaration 14 Syntax: const <data type> <name> = <value>; Example: const const int radius = 15; double area=1. 5; bool is_done=true; string movie=”Star. War. III”; char my_initial=‘m’;

Variable & Constant Multiple-Constant Declaration 15 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;

Test : Constant Declaration 16 Declare Constant Name : e Type : double Initial value : 2. 71828 const double e=2. 71828;

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

Expression C# Expression 18 Expressi on Arithmeti c Expressi on Boolean Expressi on

Arithmetic Expression 19 Operators + - * / % (modulo: remainder after division) Integer operates Integer/Real operates Real/Integer Real Example 16 11 + 5 7 39 / 5 7. 8 39. 0/5 4 39 % 5 0. 6 5. 0 % 2. 2

Arithmetic Example 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; } Answer d=2 e=0 f = 2. 5 g = 2. 5

21 Pre/Post Increment & Decrement In/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 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

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

23 Priority of Arithmetic Operators Priority Operator 1 Parentheses () 2 x++, x-- 3 ++x, --x 4 *, / , % 5 +, - 6 If equal priority, work from left to right Arithmetic

Arithmetic Example 24 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 Comparis on Given x = 3. 0, y = 2. 0, b =2, what is the output? � x/y*++b � x/y*b++ 3 � Answer: 2 4. 5 � Answer: 3. 0

Modify-And-Assign Modify-and-Assign Operations 26 Statement var += expression Description 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 /= 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)

Modify-And-Assign Example 27 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. Write. Line(sum); Console. Write. Line(prod); Console. Write. Line(y); Monito r 3 7. 5 -4

Math Class 28 Method/ 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

Example 29 What is the output? Monitor Console. Write. Line(Math. Round(3. 499)); Console. Write. Line(Math. Floor(3. 499)); Console. Write. Line(Math. Ceiling(3. 499)); 3 3 4

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))

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

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

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

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

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

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