software development program

8/3/2019 Software Development Program

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Software Development

Training Program

Zeeshan Hanif


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Cloud Computing - 101Lecture 2

Zeeshan [email protected]

[email protected]


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First C# Programusing System;

public class First

{

public static void Main(string[] args)

{

Console.WriteLine(I belong toOperation Badar);

}

}


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Parts of a C# Program Class Name

public class First

Main methodpublic static void Main(string[]args)

StatementsConsole.WriteLine(I belong to

Operation Badar);


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Bits and Bytes Bit is the smallest unit of storage

Bit is a digit that can have only twovalues: 0 or 1

A byte is made up of 8 bits

1 0 0 1 1 1 0 1

1 Byte

8 Bits


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Memory allocation10011001

11111001

01110101

10010101

11000001

10111001

01001110

11000101

Main Memory


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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


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Datatypes and size in memory Integer Types

C#Keyword

Sizebits/bytes

Signed/Unsigned

Type inSystem

Range

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


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Datatypes and size in memory Floating-Point and Decimal Types

C#

Keyword

Size

bits/bytes

Significant

Figures

Type in

System

Range

float 32 bits /

4 bytes

7 Single -3.40282347E38 to 3.40282347E381.5 * 10-45 to 3.4 * 1038

double 64 bits /

8 bytes

15 Double -1.7976931348623157E308 to1.7976931348623157E308

5.0 * 10-324 to 1.7 * 10308

decimal 96 bits /

12 bytes

28 Decimal -79228162514264337593543950335to79228162514264337593543950335

1.0 * 10-28 to 7.9 * 1028


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Datatypes and size in memory Character Types

C#Keyword

Sizebits/bytes

Type inSystem

Value

bool 8 bits / 1 byte Boolean true and false

Boolean Types

C#Keyword

Sizebits/bytes

Type inSystem

Value

char 16 bits / 2 bytes Char All Unicode Character


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Literals A value of any kind is called a literal

Integer literals

int count = 2250; / long = 7854214; Floating point literals

double d=2.5 E-5.0; / decimal f = 34.34m; Character literals

char c=B; Boolean literals

bool b=false; // also true


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Literals NOTE :

All the integer types are considered int or long typeby default.

All the floating point types are considered double bydefault.

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 4.4as float.


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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;


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Binary Representation Decimal Numbers

Binary numbers

Conversion of decimal numbers intobinary

Conversion of binary numbers intodecimal numbers


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What is a Variable? `vary`-ablemeans change-able

The variable is the basic unit of storage. A

variable is defined by the combination of atype, variable name and an optionalinitializer. In c# all variables must bedeclared before they can be used.

int a = 4;

TypeName

Initial value


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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;


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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 maycontain these characters plus the digits0 through 9.


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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


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Invalid Identifiers Followings are invalid identifiers: -

&total

Minute#

4hour

12hello abc@abc

$asdfa


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Identifiers Both uppercase and lowercase letters

can be used in an identifier. Because

C# is case sensitive, therefore these aretreated as different identifiers: -

Total

total TOTAL

toTal


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What is a Keyword?abstract default foreach null sealed uintas delegate goto object short ulong

base do if operator sizeof unchecked

bool double implicit out stackalloc unsafebreak 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


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Casting / Conversion Implicit casting

When one type of data is assigned to theother type of variable, an automatic typeconversion occurs if left hand type is largerthan the right hand type. This conversion is

sometimes called widening conversion sinceyou are converting small value to largevalue.


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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 lefthand side


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Casting / Conversion Explicit casting

When you want to assign a larger value to a smaller

value, you can not do it without explicitly casting itusing the cast operator. This conversion is sometimescalled narrowing conversion since you are explicitlymaking the value narrower to fit into the small size.

The syntax for explicit casting is:

target variable = (target) value;


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Casting / ConversionNOTE:

When you explicitly cast large value to small value

some information may be lost. For example, whenfloating point value is assigned to an integer thefractional part is lost

int a = 5;

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

byte b = (byte) a;

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