Computer Science: Networks, Python, DBMS & SQL

• This is a recording of a Computer Science teacher hosting a class to prepare students for their exam on April 2nd.
• The teacher's name is Ashmi.
• She plans to cover the whole syllabus during the session.
• Students are excited that the whole syllabus will be completed in a few hours.
• The teacher will provide a PDF of the content.

Topics to be Covered

• Data Networks and Data Communication

• Python (including file handling: Text file, Binary file, CSV)

• DBMS + SQL

• The CBSE exam on April 2nd will cover three units: Programming Thinking, Computer Network, and Databases.

• The teacher visited a temple an offered prayers for the students' success.

Computer Network

• A computer network involves communication between multiple computers through a network.
• Computers can send and receive data via a network.

Computer Networking

• A group of two or more computer systems that are interconnected.
• People communicate with each other by using computer networking.
• Networking includes social networking, mobile networking, computer networks, railway systems, and banking.

Network Example

• A network device connects to a computer, a phone, a printer, a laptop , a tablet etc.. to each other and communicate

Computer Network Size

• It can be small or bigger depending on the Computer Network, it depends on number of Computers that are Connected

• Host is a type of computer in a network. A host can also be referred to as a "node."

• Server, desktop, laptop, and circular phone are examples of entities in a network.

Evolution of Networking

• The idea of Networking Start from a Company in USA: They tried to make 2 Systems communicate with each other and Exchange DATA

• In 1961, the idea of ARPANET was created.

• ARPANET means Advanced Research Project Agency Network.

• In around 1969 Two Companies used ARPANET successfully.

• In 1971, Networking Messaging came into place and Email was invented using the @ symbol.

• In 1974, the TELNET Communication Started where file Transmission were done via Remotely and that time it was a Big thing

• In 1982, TCP/IP Was introduce which is a Standard Protocols using the ARPANET Concept

• In 1985, Domain Name System was introduced to help users remember website URL easily instead of using memorizing IPs.

• In 1986, NSFNET connected many people together through a science program.

• In 1990, HTML and URLs were introduced along with the WWW (World Wide Web).

• In 1971 a first version of WiFi was introduced to the World

Types of Computer Networks

• Types of Network: PEN, LAN, MAN and WAN

PAN (Personal Area Network)

• Devices are connected via USB
• Uses bluetooth and WiFi
• This includes your personal Phone Smartphone and Printer etc..

LAN (Local Area Network)

• This uses ethernet.
• Connects a group of computers in a single location, such as an office or school.
• Can cover a range of 1 Kilometer
• Data transmission Speed is High between 10MBPS to 1000MBPS
• 10MBPS is called Ethernet
• 1000MBPS is called Giga Ethernet

MAN (Metropolitan Area Network)

• Extends further than LAN
• Usually covering one towns and cities.
• Can cover distance up to 30 - 40 Kilometers.

WAN (Wide Area Network)

• ALL Around the World
• Connects Computers to other Networks and LAN,MAN
• Internet is considered WAN
• A WAN can be a Wired or Wireless

Network Devices

• Network Devices: Modem, Hub, Switch, Repeater, Router and Gateway

Modem

• The name Modem means Modulator and Demodulator.
• Performs analog to digital and digital to analog conversions.
• It gives the computer digital signals.
• Your Computer usually speaks Digital Information 0 and 1 language and the analog Signal is the continious WAVE Pattern
• Digital Signal then Analog Conversion then sent to another modem

Ethernet (NIC)

• Ethernet is also called NIC which means Network Interface Card
• A cable is connected to the ethernet card, to support Wired Network inside the computer.
• It is supported via Computer ports.
• Data Transmission rate is from 10 MBPS to 1 Giga Bytes

RJ45

• RJ45 is the Registered Jack 45
• Its an 8 pin Connector to transfer data from system, USB, Computer etc..
• There's an 4 PIN Connector called RJ11
• This cable is most commonly use for LAN connection and can be BLUE and White
• The Ports support LAN Cable to access INternet

Repeater

• Re-Transmits and Regenerates the Original Signal
• When there is Distance very Long, the Repeater helps Transmit with the cable the data safely

Hub

• Normal Hub always Broadcast the messages
• If the Hub received a messages, it sends it to All the devices
• Speed is affected negatively due to Traffic as the Hub Broadcast to each devices.

Switch

• No Traffic cause No Broadcast.
• Direct Message Transmission from System 1 to another
• Its a bridge which sends message destination through their addresses are knows
• For One to One type Communication use Switch, for large broadcasting use Hub

Router

• Router Decide the ROOT and Find the Messagest to send from Destination to another Destination
• Whether Wire or Not, It Find Best Route and Faster Speed
• It does this by finding IPs

Getaway

• Server One and Server Two are Dissimilar Not Same
• Gateway means the Acess Point where IN and Out come
• The entry and exit point
• Hardward and Software are implemented in Gateway

Topology

• Network topology: the arrangement of computers and other devices in a network.
• Peripheral devices are typically hardware, that are Connected to one another
• The Network Types are: Mesh, Ring, Bus, Star, Tree and Hybrid

Mesh Topology

• Every Device are Connect with Every other Devices
• Cabling cost is HIGH
• If cable have issue in Mesh, Only ONE cable is impacted.

Ring Topology

• Every device are connected to 2 devices
• Last is connected back to beginning
• Sending data across Ring is ONE Way Direction Only
• Called as UniDirectional

Bus Topology

• All the device Share a Single Cable
• End of Cable has a Terminatot
• If a Device is to be Sent, all the others receive it But they either Deny or Accept
• Traffic is high with BUS Topology, Easy to Maintain Cheap Cable
• Single Bone, the Single Cable
• Cheaper to Manintain and Easiest

Star Topology

• Centralized Node
• Very Effective, all the messages are very FAST
• The Central Node which Broadcast is called Hub
• Called as UNICAST because only One way

Tree - Hybrid

• Combination of Bus and Star
• Tree use HUB to each bus connection

Web Services Introduction

• Client -> Web Browser ( URL Request Like Python) -> Web Server ( Response Data) -> Web Page Display

• When user Click HypeLink it will give Web Pages

• website URL is your website example google.com is your website to Find and it has minimum 1 server

• Audio , Files, Images Store in WEBSITE, the space for it is called Web Hosting, it gives SPace and Data for User for websites

WWW - Worlds Wide Web

• Internet with Services

• Millions of File Collection

• The place where we find URL: Is where the webpages of HTML are Created.

• HTML - Hyper Text Markup Language

• Markup Language is where element and layoute are created in the Weebpages

• XML is Extended Markup Language where you do not have Preset of Anything as XML is a Template set for User

HTTP

• HTTP -Hyper Text Transfer Protocol allows the Data to Transfer from the Client such as Request and Response

Domain Name

• Unique name that allow remember website url
• Every website on the internet has a ip address: that's why it gives website a more convenient url

URL

• Uniform Resource Locator
• It is where we locate Address of Web Pages and Direct the request

Website

• Website is collection of WeebPages (Pages) of a Book
• Single Page is Web Page and Main Page called HOME PAGE

Web Browser

• Client Software
• You request through HTTP and the Web Page is Delivered with HTML

Web Hosting

• Storage for All websites is where we create website like files of video audio etc.. which can accessed by publics

Protocols In Communication

• Protocols In Communication has a Set of Rules for Senter and Receiver for Communication

• The Protocls In communication are: TCP/IP, HTTP, FTP, SMTP, POP3, TELNET etc...

• The HTTP Protocal is a Transfer of Data from Client and Servier

• The FTP is File Transfer Protocol that Transfers Files across computer.

• SMTP is Simple Mail, Transfers emails to each other

• POP3 means the post office protocal

TCP/IP

• TCPIP : Transmission Control Protocol, Oldest way that ensure Computer communicate easily
• Client server model, connect Senter to Receivee

POP 3

• Post Office Protocol Version 3
• It is Latest Operation used on Web Mail such as gmail to send the email

TELNET

• TELNET Remote into Another Computer Via CHARACHTER by CHARACHTER Basis by first accesssing that Remote, then login to the system

Data Communication

• Raw facts and Figures such as Audio Video
• A System sends and recieves to another
• Device can include phone laptop
• Component has (Sender, Reciever, Communication Device )

Sender

• computer sends Data

Reciever

• Computer Laptop Sends Data

Message

• Text, Audio, VIDEO etc..

Transmission Media

• The Medium of the data
• such as VIA Wired or Wireless

Protocol

• THE set of Rules
• EX) Ehternet or HTTP

Measure communications capacity

• Transfer to Another source
• Bandwidth tells the ranges from Frequency
• MBPS means megabite per second
• 4 Bits is Nibble
• 8 Bits is Byte
• Biggest to Smallest : TB, GB, MB KB then Nibble

Switching Techniques are:

• 1 to 1 Connections between Reciever and sender
• Temporay Channel Root

Circuit Switching

• Connection between a root before Communicating
• Communication happens from before and the connection STAYS

Packet Switching

• Information is broken into Small Pieces, sent with the other packets that was taken by the Sender.

• Adress comes in 2 forms: IP Format Number wise (logic) vs Mac Physical Addres unique to manufactiuring

• IP is more of Logic for 123123 type thing and MAC is more of Physical to identify Network

• there are 2 types of IP v4 vs v6

• v4 was 32 Bits 4 Octet and that is between 0 between 255

• v4 example format: 0.0.0.0 to 255.255.255.255.

• v6 is what allow many more people to do (128 bits and 8 Octets.

• v6 Format using HexaDecimal AFFF type format

• Mac Adress is Media Access Control unique per system

Transfer of data to system can be:

• Via Wired or Wireless
• WIred includes TV Twisted Pair Cable (Copper)
• Coaxial Cable has copper code (Used for TV cables for Internet)
• Fiber-optic use Thin Glass that use Light instead of Electricity
• These fiber optics are then put together into cables.

Wireless

• WIreless uses Radiowave
• Electromagnatic waves is the Transfer.
• Radio Frequency: 3khz - range is Long distance
• MW Microwave: UniDirectional, Short Disty

Functions in Python

• FUNCTIONS (Take large to small) Breaks up tasks that is a module which we reuse: That way we call functions Functions comes in 3 types: Built in, Module, User

Functions Python list

• Build in = Easy like quick print - that happen alread, int Module = is predefine like MATH where we import but need to declare. Math Example use prebuilt like squareroot User defined: is what USER creates: like your own defined module

• Function CALLS call FUNCTION or EVoke it:

• EXAMPLE

def sum(x,y)
  Print(x+y)

• The Print is the Fucntion body:
• When we write Header of Function is where you place paramaters

Paramaters vs Argument

• Paramater is We Right Header that is where WE see the value

• Arguements = Where you are passing data

• Another meaning is Formals parameter (paramater vs actual = arguement)

Type Arguement are:

• Positional

• Diffrentiatial

• Positionals: Is order

• Diifrenshiatial is: what is defined before

Scope of Variable are:

• If only in function that means local varaible
• The variable for the program is GLobal.
• Variable :
• -Example int = 1 (the 1 is variable as can be diffrent)

Flow Exeuction

• The program Starts from Top all the ways down

Example Python

def Function:
    printhello
    printworld
FUNTION()

What is recusion

• Very Powerful Program language where funnction self calls Comse in 2 types (Diect and InDieect) Example where self runs Indirect has like 2 functions where the A function needs the other

Example

A()
Print"hel" function repeats

Inifnity Loop If condition is not true this continue The condition not true mean loops go with out true Loop Ender the Loop

Base Condition (What you know)

Exception Handling

• Error = Compile Time. Run time. Logical 0 Compile: Typo Wrong order Run time: Cant handle when running. Not clear Logical: Mistake program when it is Wrong

Try BlocK: Run Except: Excepting Final Try, if error.

• Example: Check If: try 1
• Exception: Is an alert. Handled
• else handled (print not work)

FinanlL: EXXEUTE EVERYTIEM!!!

All file come down t: Text File, Binary file, Csv File! TEXT FILE is a sequence

• Examples ASCII,

• Binary are code and images for files for operation CSV - Comma seperated Value.

• ABSOLUTE vs Relative Absloute is The full Path to Computer Relative is just Folder name

• Main issue:

• Read: Charachters. Open

• write: Write String Comman seperation

• CSV 1 Read Module: Read WRite Module: WRite

Database Concepts

• Dta is raw. Uonroganzier database organized is. Collection of data

• Dbmx example mysquell, orcale access

REDUNDAncy Sharind EasY data Secure!!!!!

TABLE format. RELATION Database Etributes is table is description top columns Tuple are the rows Degree the number

Primary key UNique. Un Canidate key can that be.

SQL.

• SELECT data

Example

Update employee set saler =2

Select
From
What