working with variables, operators and expressions

FACULTY OF IMFORMATION TECHNOLOGY

Author: Nguyen Ngoc Khuong– Phone : 0976649996- Email: khuongnn.mcs09@vnuedu.vn– Blog: http://khuongfit.wordpress.com

HAI PHONG UNIVERSITY

Working with Variables, Operators and Expressions

Statements-Comments

Identifiers Variables

Primitive Data Types

Arithmetic Operators

Implicitly Typed Local

Variables

Incrementing & Decrementing

Variables

Statements-Comments

-A Statement is a command that performs an action, you must add “;” the end of command-Ex: Console.Write(“Hello C# ”);

-Comments use to explain for your CodingHow to write comments???See next slide…

//Comment 1

/* *Comment 2 */

/*Comment 3*/

/// <summary>///Write Comment 4/// </summary>/// <param name=“a"></param>/// <param name=“b"></param>private void func1(int a,float b)

Identifiers2

Identifiers are names use to identify the elements in program, ex: namespace, class, method…Syntax Rules:-Only use letter, digit, underscore-An identifier must start with a letter or an underscore-C# is a case –sensitive : nTest and ntest is different identifier

abstract do in protected trueas double int public trybase else interface readonly typeofbool enum internal ref uintbreak event is return ulongbyte explicit lock sbyte uncheckedcase extern long sealed unsafecatch false namespace short ushortchar finally new sizeof usingchecked fixed null stackalloc virtualclass float object static voidconst for operator string volatilecontinue foreach out struct whiledecimal goto override switchdefault if params thisdelegate implicit private throwdynamic join setfrom let valueget orderby vargroup partial whereinto select yield

Identifying Keywords

- A variable is storage location that holds a value. It as a box in the Computer’s memory holding temporary information.-To easy coding:+Don’t start an identifier with underscore+Don’t different only by case ( nTest and ntest)+Start name with lower case +….

Variables3

How to declare variables?

Data_type NameVariable;int nNumberOfElement;string strFullName;float fValue=0,fResult;

Data Type Description Size(bits) Range Exampleint Whole numbers 32 –231 through 231 – 1 int nSize;

long Whole numbers(bigger range) 64 –263 through 263 – 1 long lSize;

float Floating-point numbers 32 ±1.5 × 1045 through

±3.4 × 1038 float fDelta;

double Double-precision (more accurate) floating-point numbers

64 ±5.0 × 10−324 through ±1.7 × 10308 double dDelta;

decimal Monetary values 128 28 significant figures decimal decKe;

string Sequence of characters

16 bits per character Not applicable string strName;

char Single character 16 0 through 216 – 1 char chrAns;bool Boolean 8 True or false bool bRet;

Primitive Data Types4

You should initialize value for variableint nSize=0;String strName=“”;

Arithmetic Operators

/ % ()int nPlusTwoNumber=113 + 114The + is the operator113 and 114 are the operands

Not all operators are applicable to all data typesExample:You will get compiler error with the statements:Console.WriteLine(“Tý” - “Tèo”);

How to convert from String to Number Format ?int nValue=System.Int32.Parse("113");double dValue = System.Double.Parse("3.5");

Datatype vName=System.DataTypeObject.Parse(“string”);

Incrementing & Decrementing

Variables

X++Postfix

increment

++XPrefix

increment

X--Postfix

decrement

--XPrefix

decrement

Implicitly Typed Local

Variables

var sAny;Error: Implicitly-typed local variables must be initialized

var number1=1;var strAny=“tèo”;

working with variables, operators and expressions

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