Software Development Training Program

KAZIM HUSSAIN

First C# Program

using System;public class First{public static void Main(string[] args){

Console.WriteLine(“I belong to Operation Badar”);

}}

Parts of a C# Program Class Name public class First

Main methodpublic static void Main(string[] args)

StatementsConsole.WriteLine(“I belong to

Operation Badar”);

Bits and Bytes Bit is the smallest unit of storage Bit is a digit that can have only two

values: ‘0’ or ‘1’ A byte is made up of 8 “bits”

1 0 0 1 1 1 0 1

1 Byte

8 Bits

Memory allocation 

 

 

 

 

 

 

 

10011001

11111001

01110101

10010101

11000001

10111001

01001110

11000101

Main MemoryMain Memory

Types of Data: “Datatypes” Data types are very important in

every language for storing and manipulating data

Different kinds of data exist All have different features hence

difference requirements Nature of data determines its

“type”

Datatypes and size in memory Integer Types

C# Keyword

Sizebits/bytes

Signed/ Unsigne

d

Type in Syste

m

Range

sbyte 8 bits / 1 byte signed SByte -128 to 127

byte 8 bits / 1 byte unsigned

Byte 0 to 255

short 16 bits / 2 bytes

signed Int16 -32765 to 32768

ushort 16 bits / 2 bytes

unsigned

UInt16 0 to 65535

int 32 bits / 4 bytes

signed Int32 -2147483648 to 2147483647

uint 32 bits / 4 bytes

unsigned

UInt32 0 to 4294967195

long 64 bits / 8 bytes

signed Int64 -9223373036854775808 to -9223373036854775807

ulong 64 bits / 8 bytes

unsigned

UInt64 0 to 18446744073709551615

Datatypes and size in memory Floating-Point and Decimal Types

C# Keywor

d

Sizebits/bytes

Significant Figures

Type in System

Range

float 32 bits / 4 bytes

7 Single -3.40282347E38 to 3.40282347E38 1.5 * 10-45 to 3.4 * 1038

double 64 bits / 8 bytes

15 Double -1.7976931348623157E308 to 1.7976931348623157E308 5.0 * 10-324 to 1.7 * 10308

decimal 96 bits /12 bytes

28 Decimal

-79228162514264337593543950335 to 79228162514264337593543950335 1.0 * 10-28 to 7.9 * 1028

Datatypes and size in memory Character Types

C# Keyword

Sizebits/bytes

Type in System

Value

bool 8 bits / 1 byte Boolean true and false

Boolean Types

C# Keyword

Sizebits/bytes

Type in System

Value

char 16 bits / 2 bytes

Char All Unicode Character

Literals A value of any kind is called a literal Integer literals

int count = 2250; / long = 7854214;

Floating point literalsdouble d=2.5 E-5.0; / decimal f = 34.34m;

Character literals char c=‘B’;

Boolean literals bool b=false; // also ‘true’

Literals NOTE : All the integer types are considered int or long

type by default. All the floating point types are considered double

by default.

So if you want to store 4.4 in float datatype you can not write this: - float f = 4.4; / decimal d = 4.4;

Instead you write float f = 4.4f; decimal d = 4.4m; This way you explicitly tell the compiler to treat

4.4 as float.

Literals If you want to add two byte or

short like: byte a = 5; byte b = 5; byte c = a+b;

Instead you write byte a = 5;

byte b = 5; int c = a+b;

Binary Representation Decimal Numbers Binary numbers Conversion of decimal numbers

into binary Conversion of binary numbers

into decimal numbers

What is a Variable?

`vary`-able means change-able The variable is the basic unit of storage.

A variable is defined by the combination of a type, variable name and an optional initializer. In c# all variables must be declared before they can be used. int a = 4;Type

Name

Initial value

Example Some variable declarations examples: - 1. int a = 3; 2. int x,y,z;

x = 4;y = 6;z = 3;

3. char c = ‘a’; 4. bool b = true; 5. double d = 44.4, v = 43.3;

What is a Identifier? Identifiers are used to name

variables, classes, interfaces, methods, and other elements.

An identifier is a sequence of characters that starts with an underscore (_), or a letter. Subsequent characters may contain these characters plus the digits 0 through 9.

Rules for Identifiers A-Z, a-z, 0-9,_,@ Must not start with digit So followings are valid identifiers: - _minute total Sum4 Hello67_hello @abc_34 _34343

Invalid Identifiers Followings are invalid identifiers: - &total Minute# 4hour @12hello abc@abc $asdfa

Identifiers Both uppercase and lowercase

letters can be used in an identifier. Because C# is case sensitive, therefore these are treated as different identifiers: -

Total total TOTAL toTal

What is a Keyword?abstract default foreach null sealed uint

as delegate goto object short ulong

base do if operator sizeof unchecked

bool double implicit out stackalloc unsafe

break else in override static ushort

byte enum int params string using

case event interface private struct virtual

catch explicit internal protected switch void

checked extern is public this while

class false lock readonly throw

const finally long ref true

continue fixed namespace

return try

decimal float new sbyte typeof

Casting / Conversion Implicit casting

When one type of data is assigned to the other type of variable, an automatic type conversion occurs if left hand type is larger than the right hand type. This conversion is sometimes called widening conversion since you are converting small value to large value.

Casting / Conversionbyte a = 5;int b = a;long c = b;double d = c;

All the above are implicit type casting examples. The right hand side is smaller than the left hand side

Casting / Conversion Explicit casting

When you want to assign a larger value to a smaller value, you can not do it without explicitly casting it using the cast operator. This conversion is sometimes called narrowing conversion since you are explicitly making the value narrower to fit into the small size.

The syntax for explicit casting is: target variable = (target) value;

Casting / Conversion

NOTE:When you explicitly cast large value to small value some information may be lost. For example, when floating point value is assigned to an integer the fractional part is lost

int a = 5;

byte b = a;The second line will cause error. You can cast the second line like this using cast operator.byte b = (byte) a;