Computers and Networks: Understanding IT Components, Human Interaction, and Cybersecurity, Sintesi del corso di Informatica gestionale

Scarica Computers and Networks: Understanding IT Components, Human Interaction, and Cybersecurity e più Sintesi del corso in PDF di Informatica gestionale solo su Docsity! TOPIC 1 Infromation technology (IT)  describes any technology that helps to produce, manipulate, store, communicate, and/or disseminate information Components of (IT) Computer is an electronic system that can be instructed to accept, process, store and present data and information. Computers are very powerful at looking through large amounts of data quickly. Computers can perform billions of operations per second. Turing test, test of a machine’s ability to exhibit intelligent behavior equivalent to that of a human: proposed that a human evaluator would judge natural language conversations between a human and a machine designed to generate human-like responses. Test requires 3 terminals: - One terminal is operated by a computer, while the other two are operated by humans - During the test, one of the humans functions as the questioner, while the second human and the computer function as respondents - After a present length of time or number of questions, the questioner is then asked to decide which responded was human and which was a computer IT components: internet application, network, application software, operating system, hardware Hardware includes the physical parts of a computer, such as the case, central processing unit (CPU), monitor, mouse, keyboard, computer data storage, graphics card, sound card, speakers and motherboard 5 computer types: - Supercomputers: A supercomputer is a computer with a high level of performance compared to a general-purpose computer. Performance of a supercomputer is measured in floating-point operations per second (FLOPS) instead of million instructions per second (MIPS) - Mainframe computers: mainframe computers are used primarily by large organizations for critical applications; bulk data processing, such as census, industry and consumer statistics, enterprise resource planning; and transaction processing - Workstations: Used for scientific, mathematical, engineering, computer-aided design (CAD), computer-aided manufacturing (CAM) - Microcomputers: personal computers, types include desktop, tower, notebooks,… - Microcontrollers: Also called embedded computers. Tiny, specialized microprocessors inside appliances and automobiles; They are in microwaves, programmable ovens, blood- pressure monitors, air bag sensors Personal computer: scanner, CPU (microprocessor), memory (RAM), expansion cards, power supply, optical disc drive, storage (hard disk).  CPU components include: The arithmetic logic unit (ALU), which performs arithmetic and logical operations; The control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary Machine cycle: Is defined as the steps performed by the computer processor for each machine language instruction received. 4 process cycle that include: 1. Fetch - Retrieve an instruction from the memory; 2. Decode - Translate the retrieved instruction into a series of computer commands; 3. Execute - Execute the computer commands; 4. Store - Send and write the results back in memory Memory hierarchy: In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Software  is a general term for the various kinds of programs used to operate computers and related devices. Often divided in into: - System software: which includes operating systems and any program that supports application software - Application software: programs that do work users are directly interested in 1 System software (operating system) An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. System Software includes operating systems and any program that supports application software OS: windows, Mac OS, android, iOS,…  the other programs are called application programs Application software (app)  is a computer program designed to help people perform an activity. Depending on the activity for which it was designed, an application can manipulate text, numbers, audio, graphics, and a combination of these elements. Application Software Install after the OS AND Application depends on OS(for example Linux applications won’t work on Windows and viceversa). Main key concepts: 1. Purpose of a computer: turn data into information; Data = the raw facts and figures; Information = data that has been summarized and manipulated for use in decision making 2. Hardware vs software: The term hardware describes the physical aspects of computers and related devices; Hardware is the machinery and equipment in the computer. Software is the electronic instructions that tell the computer how to perform a task; Software is the variable part of a computer and hardware the invariable part. 3. The basic operations: Input: What goes into the computer system; Processing: The manipulation a computer does to transform data into information; Output: What comes out; Numbers or pictures on the screen, printouts, sounds; Communications: Sending and receiving data; Storage Storage capacity is represented in bytes: Permanently installed: floppy drives, hard drives, Zip drives; Removable media: floppy disks, CDs, DVDs, flash pen drives. Internet application  is a type of applications that use the internet for operating successfully, that is, by using the internet for fetching, sharing and displaying the information from the respective server systems. It can be accessed only with the help of the internet facility, and it cannot be functional without the internet. Top 8 internet applications are the following: Smart Home, Electronic Devices, Automated Digital Technology, Industrial Internet, Smart City, Smartphones, Smart Grids, Major Application. Internet  is a worldwide system of computer networks - a network of networks – in which users at any one computer can get information from other computer. It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in 1969 and was first known as the ARPAnet Characteristics of internet: - Distributed ownership: Different portions of the Internet are owned by different entities - Multiplicity of devices: The Internet consists of millions of smaller digital networks, a collection of digital devices (nodes) - Open standards: The agreed upon set of rules or conventions governing communication among Internet nodes are freely available to everyone - The Internet is rapidly evolving: Network and grid computing; Wired and wireless connections of a range of intelligent devices WWW (world wide web)  is an information system where documents and other web resources are identified by Uniform Resource Locators (URLs, such as https://example.com/), which may be interlinked by hyperlinks and are accessible over the Internet. The resources of the Web are transferred via the Hypertext Transfer Protocol (HTTP), may be accessed by users by a software application called a web browser and are published by a software application called a web server. Web browsing is done with a Web browser, the most popular of which are Chrome, Firefox and Internet Explorer. Tim Berners-Lee invented the World Wide Web in 1989. He wrote the first web browser in 1990 while employed at CERN in Switzerland. TOPIC 2 2 verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Blockchain  is a digitized, decentralized, public ledger of all cryptocurrency transactions. The most recent transactions are recorded and added to it in chronological order. Each node, that is a computer connected to the network, gets a copy of the blockchain, which is downloaded automatically. A block is the ‘current’ part of a blockchain, which records some of the recent transactions. Once completed, a block goes into the blockchain as a permanent database. Each time a block gets completed, a new one is generated. The blockchain was designed so these transactions are immutable, meaning they cannot be deleted. Robotics is a branch of engineering that involves the conception, design, manufacture, and operation of robots. This field overlaps with electronics, computer science, artificial intelligence, mechatronics, nanotechnology and bioengineering. These technologies deal with automated machines that can take the place of humans in dangerous environments or manufacturing processes, or resemble humans in appearance, behavior, and or cognition. Assisted transportation An intelligent transportation system (ITS) is an advanced application which, without embodying intelligence as such, aims to provide innovative services relating to different modes of transport and traffic management and enable users to be better informed and make safer, more coordinated, and 'smarter' use of transport networks. (car navigation; traffic signal control systems; container management systems; variable message signs; automatic number plate recognition). Assisted reality and virtual reality (AR/VR) Augmented reality is the integration of digital information with the user's environment in real time. Unlike virtual reality, which creates a totally artificial environment, augmented reality uses the existing environment and overlays new information on top of it Virtual reality is an artificial environment that is created with software and presented to the user in such a way that the user suspends belief and accepts it as a real environment. On a computer, virtual reality is primarily experienced through two of the five senses: sight and sound. Assisted reality refers to any technology that allows a person to view a screen within his or her immediate field of vision, hands free. It differs from augmented reality in that the information on the screen is not overlaid onto a physical environment. Now, assisted reality may not be as glamorous as augmented reality, but it’s arguably more accessible and practical for field service technicians, mechanics, and other service professionals to use right now. In contrast, augmented reality is still in its early stages. Data science is an interdisciplinary field that uses scientific methods, processes, algorithms and systems to extract knowledge and insights from data in various forms, both structured and unstructured; is the study of where information comes from, what it represents and how it can be turned into a valuable resource in the creation of business and IT strategies. practitioners apply machine learning algorithms to numbers, text, images, video, audio, and more to produce artificial intelligence (AI) systems that perform tasks which ordinarily require human intelligence. In turn, these systems generate insights that analysts and business users translate into tangible business value. Cloudification A native cloud application (NCA) is a program that is designed specifically for a cloud computing architecture. NCAs are designed to take advantage of cloud computing frameworks, which are composed of loosely-coupled cloud services. That means that developers must break down tasks into separate services that can run on several servers in different locations Smart cities A smart building is any structure that uses automated processes to automatically control the building’s operations including heating, ventilation, air conditioning, lighting, security and other systems. Helps owners, operators and facility managers improve asset reliability and performance, which reduces energy use, optimizes how space is used and minimizes the environmental impact of buildings. 5 A smart city is a designation given to a city that incorporates information and communication technologies (ICT) to enhance the quality and performance of urban services such as energy, transportation and utilities in order to reduce resource consumption, wastage and overall costs. The overarching aim of a smart city is to enhance the quality of living for its citizens through smart technology. Internet of things (IoT) is the extension of Internet connectivity into physical devices, vehicles, home appliances and other items embedded with electronics, software, sensors, actuators, and connectivity which enables these things to connect and exchange data, creating opportunities for more direct integration of the physical world into computer-based systems, resulting in efficiency improvements, economic benefits. By connecting devices to the internet, and to one another, information can be shared and used to influence the other devices in the network. This allows our objects to behave more intelligently and, in turn, behave more efficiently TOPIC 3 Humans interpret words and pictures, while computers interpret only patterns of bits BIT is an abbreviation of binary digit and represents the smallest piece of data having just two possible values as either of the binary digits 0 or 1 BYTE is a group of eight bits. A byte is the smallest possible addressable unit of computer storage. The term, “addressable” means that a particular byte can be retrieved according to its location in memory. Each time a bit is combined with another bit, more different combinations can be stored. Hence, if we have 4 bits, we will have 2^4 = 16 different combinations. A word is a contiguous group of bytes  Words can be any number of bits or bytes; Word sizes of 16, 32, or 64 bits are most common A group of four bits is called a nibble. Bytes store numbers using the position of each bit to represent a power of 2  The binary system is also called the base-2 system.  How is a letter converted to binary form and back? When a letter is pressed on a keyboard, the electronic signals are converted into binary form and stored into memory. Then the computer processes the data as bytes of information and converts them to the letters we see on the monitor screen or on printed page.  What is the memory? Electronic components that store instructions, data, and results; Consists of one or more chips on motherboard or other circuit board. Each byte is stored in unique location called an address, like addresses on a passenger train Memory is measured by number of bytes available for storage: A Kilobyte (KB) is a thousand bytes; A Megabyte (MB) is equals to exactly one millions bytes; A Gigabyte (GB) is equals to one billion bytes.  popular coding systems to represent data: ASCII - American Standard Code for Information Interchange; Unicode - coding scheme capable of representing all world’s languages ASCII: Use 7 bits to represent a character. Consists of 2^7 = 128 character in the 7 bits code. Primarily used on PC and Server Extended ASCII: use 8 bits to represent a character. Consists of 2^8 = 256 character, where the first 128 characters are the same as ASCII. It is important that all computers use ASCII as otherwise different codes would represent different values UNICODE: is an international and multilanguage text character and coding system. Use more bits and therefore can be used for more character combinations. 16 bits and maximum 32 bits to represent a character. Implemented in several OS (Windows, Mac OS, Linux). It allows all written language of the world to be represented using a single character set. 6 IP ADDRESS: 32-bit binary sequence of 1s and 0s is an IP address. IP is short for Internet Protocol and represent a unique identifier for a computer or device (host) on a TCP/IP network. Are written in a so-called dotted decimal notation. Purpose of IP address Unique Identification of source and destination. Identifies a machine’s connection to a network. Physically moving a machine from one network to another requires changing the IP address. There are 5 Classes of IP address: Class A reserved for governments → begins 1 to 126; Class B reserved for medium companies → begins 128 to 191; Class C reserved for small companies → begins 192 to 223; Class D are reserved for multicasting → begins 224 to 239; Class E are reserved for future use → begins 240 to 254 IP address can be: - Static IP address: manually input by network administrator; manageable for small networks; requires careful check to avoid duplication - Dynamic IP address: Assigned by the Dynamic Host Configuration Protocol (DHCP: a service running on the network); Derived automatically from a range of addresses IP versions: - IPv4: It is the fourth revision in the development of the Internet Protocol (IP) and the first version of the protocol to be widely deployed. It is at the core of standards-based internetworking methods of the internet. Written in Dotted Decimal Notation - IPv6: All addresses are 128 bits Write as sequence of eight sets of four hex digit (16 bits each) separated by colons. Written in Hex Decimal Notation Determine IP address: Microsoft Windows Users Click Start/Run and type: cmd o command to open a Windows command line; From the prompt, type ipconfig and press enter. DNS DNS provides a mapping of IP Addresses to names and vice versa. Computers may be moved between networks; in which case their IP address will change BUT their names can remain the same Determine the IP address of another computer or website: must have the computer name or domain name Microsoft Windows Users: Click Start/Run and type: cmd o command to open a Windows command line ➢ From the prompt, type ping command followed by website and press enter. TOPIC 4 Network basics: - Bandwidth is an expression of how much data – text, voice, video and so on – can be sent through a communications channel in each amount of time - Baseband is a slow type of connection that allows only one signal to be transmitted at a time. (e.g., Telephone) - Broadband is a high-speed connection that allows several signals to be transmitted at once. (e.g., Cable Television) Computer network: A system of interconnected computers, telephones, or other communications devices that can communicate with one another and share applications and data Building blocks networks: - Workstations: include laptops, desktop computers, tablets, phones, or any other device made to connect to a network and do tasks - Network application: are programs and resources that can be shared through the network. Applications can be shared with everybody or have restrictions placed on them so only a few people can access them (Network Building Blocks). Without applications, there would be little need for a network to exist. - Network Type: WAN – Wide Area Network Covers a wide geographic area, such as a country or the world; MAN – Metropolitan Area Network Covers a city or a suburb; LAN – Local Area Network Connects computers and devices in a limited geographic area such as an office, building, or group of nearby buildings; PAN – Personal Area Network Uses short- 7 2. Using a common syntax: the data are converted to a form expected by the destination. This may include a different character code, the use of encryption and/or compression 3. Segmenting the data: TCP may break the data block into a number of segments keeping track of their sequence. Each TCP segment includes a header containing a sequence number and a frame check sequence to detect errors 4. Duplicating segments: A copy is made of each TCP segment in case the loss od damage of a segment necessitates retransmission. When an acknowledgment is received from the other TCP entity, a segment is erased 5. Fragmenting the segments: IP may break a TCP segment into a number of datagrams to meet size requirements of the intervening networks. Each datagram includes a header containing a destination address, a frame check sequence and other control information 6. Framing: An ATM header is added to each IP datagram to form ad ATM cell. The header contains a connection identifier and a header error control field 7. Transmission: Each cell is transmitted over the medium as a sequence of bits Action of router: 8. Arriving at router: The incoming signal is received over the transmission medium and interpreted as a cell of bits 9. Processing the cell: The ATM layer removes the cell header and processes it. The header error control is used for error detection. The connection number identifies the source 10. Routing the packet: IP examines the IP header and makes a routing decision. It determines which outgoing link is to be used and then passes the datagram back to the link layer for transmission on that link 11. Forming LCC PDU: An LLC header is added to each IP datagram to form a LLC PDU. The header contains sequence number and address information 12. Framing: A MAC header and trailer is added to each LLC PDU, forming a MAC frame. The header contains address information and the trailer contains a frame check sequence 13. Transmission: Each frame is transmitted over the medium as a sequence of bits Action of receiver: 14. Arriving at destination: The incoming signal is received over the transmission medium and interpreted as a frame of bits 15. Processing the frame: The MAC layer removes the header and trailer and processes them. The frame check sequence is used for error detection 16. Processing the LLC PDU: The LLC layer removes the header and processes it. The sequence number is used for flow and error control 17. Processing the IP datagram: IP removes the header. The frame check information are processed 18. Processing the TCP segment: TCP removes the header. It checks the frame check sequence and acknowledges if there is a match and discards for mismatch. Flow control is also performed 19. Reassembling user data: If TCP has broken the user data into multiple segments, these are reassembled and the block is passed up to the application 20. Delivering the data: The application performs any needed transformations including decompression and decryption and directs the data to the appropriate file or other destination  Internet: is a worldwide system of computer networks - a network of networks – in which users at any one computer can get information from other computer  The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. How does the internet works? The internet consists of thousands of smaller networks; These link educational, commercial, nonprofit, and military organizations. Most are Client/Server networks. TOPIC 5 10 The internet came first  Internet is a global computer network made up of thousand of computers & computer network. WWW, or simply Web, is a way of accessing information over the medium of the Internet  So the Web is just a portion of Internet. The Internet originated as ARPANET in September 1969 and had two main goals: 1. Allow scientists at different physical locations to share information and work together 2. Function even if part of the network were disabled or destroyed by a disaster What is web? consists of information organized into Web pages containing text and graphic images. It contains hypertext links, or highlighted keywords and images that lead to related information. A collection of linked Web pages that has a common theme or focus is called a Web site. The main page is called the site’s home page. A Web Server is a computer that delivers requested Web pages to your computer. Structural components: - Hypertext: t is text which is not constrained to be linear; is text which contains links to other texts - Web portals: is a gateway website that offers a broad array of resources and services, online shopping malls, email support, community forums, stock quotes, travel info, and links to other categories (example google, yahoo…) - Search engine: is a software system that is designed to search for information on the World Wide Web - Web browser: is a software application for retrieving, presenting and traversing information resources on the World Wide Web (safari, chrome, Firefox) - Home page: A home page is the first page that you see when you open your web browser. Web pages provide links to other related Web pages. Downloading is the process of receiving information - Web address: A Web page has a unique address called a URL or Web address Semantic components: - HTTP: The HTTP is the Web’s application-layer protocol for transferring various forms of data between server and client like plaintext, hypertext, image, video and sounds. HTTP is used for communicating between Web Client and Web Server. Once the connection is established, the browser and the server processes access TCP through their socket interfaces.  Request message sent by a client: request line  the first line of an HTTP has 3 fields: 1. Method: can take on several different values (the majority is the GET method), 2. URL, 3. Protocol version.  Request message sent by a server: status line  the first line of an HTTP response message has 3 fields: 1. Protocol version, 2. Status code, 3. Status message. Common status code: 200 OK (request succeeded), 301 Moved Permanently (request object has been permanently removed), 400 Bad Request (generic error code, request not understood by server), 404 not found (request document does not exist on this server), 505 internal server error (the serve encountered an unexpected condition) - HTML: Hypertext Markup Language, is the language used to create Web pages. Uses tags, to tell the Web browser software how to display the text contained in the document. A tag is a keyword enclosed by angle brackets (Example: <I>). The text in these tags is not displayed, but parsable and tells the browsers (or other web services) specific information about the page. Simply, it “explains” the page so a browser can understand it. The opening and closing tags use the same command except the closing tag contains and additional forward slash /. All HTML documents should have html, head and body tags, along with the DOCTYPE identifier:  !DOCTYPE: tells the browser which set of standards the page adheres to  <html>…</html>: surrounds the contents of the entire page  <head>…<head>: Lists the identification information on the page, such as the title 11  <title>…</title>: Gives the name of the page that appears in the top of the browser window  <body>…</body>: Frames the content of the page to be displayed in the browser link tag: is a reference (an address) to a resource on the web; Link Tag can point to any resource on the web: an HTML page, an image, a sound file, a movie… image tag: To display an image on a page, you need to use the src attribute (stand for source). The value of the src attribute is the URL of the image you want to display on your page What is an e-mail? E-mail (electronic mail) is a method of sending messages and attaching files over the Internet. E-mail can be as simple as a few lines of text or include attachments such as pictures or documents. Email service provider (ESP) is a company that offers email services (yahoo mail, gmail), is also a company that offers email marketing or bulk email services. SMTP (Simple Mail Transfer Protocol) determines which paths an email message takes on the Internet. There are two protocols used for retrieving email: POP (Post Office Protocol) handles incoming messages and IMAP (Internet Message Access Protocol) used to deliver mail. Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (email) transmissionis a simple ASCII protocol that is based on client-server model. Clients and Servers have two main components: User Agents (UA) Prepares the message, encloses it in an envelope. (ex. Thunderbird, Eudora) and Mail Transfer Agent (MTA client) Transfers the mail across the internet (ex. Sendmail, Exim). Before transporting the sender’s message Source Mail Server forms for it an Envelope, When message is delivered, the Destination Mail Server removes Envelope and puts message into Receiver’s mailbox. What is spam? refers to the use of electronic messaging systems to send out unrequested or unwanted messages in bulk. Spammers possibly got your E -mail address because: You provided your E -mail address on shoddy sites (E.g., Free music or software download websites); You signed up for newsletters on sites that have no privacy policies; You put your E -mail address on a web page. Spammers succeed when even a small number of people reply to and purchase some spam- based offering for the spammers to succeed. Types of spam: - Commercial advertisement: When businesses capture your email address, they often subscribe you to their newsletter by default, as a low-cost way to sell their products - Antivirus warning: These emails warn you about a computer virus infection and offer a solution to fix the alleged cyber threat. But taking the bait and clicking the link can grant the hacker access to your system or may download a malicious file. - Email spoofing: In a spoofing attack a spammer picks a company brand victims will trust, such as a bank or an employer, then uses the company's exact formatting and logos. - Money scams: The spammer fabricates a story about needing funds for a family emergency or a tragic life event  Phishing is a form of fraud in which an attacker masquerades as a reputable entity or person in email or other communication channels to steal your valuable personal data (credit card, passwords, …) the attacker uses phishing emails to distribute malicious links or attachments that can perform a variety of functions. Successful phishing messages are difficult to distinguish from authentic messages: a phishing email can include corporate logos and other identifying graphics and data collected from the company being misrepresented. Types of Phishing: - Spear phishing attacks: are directed at specific individuals or companies, usually using information specific to the victim that has been gathered to more successfully represent the message as being authentic. Might include references to coworkers or executives at the victim's organization, as well as the use of the victim's name, location or other personal information. - Whaling attacks: are a type of spear phishing attack that specifically targets senior executives within an organization, often with the objective of stealing large sums. Those 12 supporting a virtual server are being taxed too much, they can adjust the number of resources allocated to that virtual server. Server templates can be created in a virtual environment to be used to create multiple, identical virtual servers. Virtual servers themselves can be migrated from host to host almost at will. Properties of virtual machines: - Partitioning: Run multiple operating systems on one physical machine; Divide system resources between virtual machines - Isolation: Provide fault and security isolation at the hardware level; reserve performance with advanced resource controls - Encapsulation: Save the entire state of a virtual machine to files; Move and copy virtual machines as easily as moving and copying files - Hardware independence: Provision or migrate any virtual machine to any physical server Type of virtualization: server virtualization, network virtualization, desktop virtualization  cloud computing: is a general term for the delivery of hosted services over the internet; enables companies to consume a compute resource, such as a virtual machine (VM), storage or an application, as a utility rather than having to build and maintain computing infrastructures in house Cloud deployment models: - Private cloud: The cloud infrastructure is operated solely for an organization. It may be managed by the organizationor a third party and may exist on premise or off premise - Community cloud: The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on premise or off premise - Public cloud: The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services - Hybrid cloud: The cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability Services provided by clouds: - Cloud software as a service: is a type of cloud that offers an application to customer or organizations through a web browser - Cloud infrastructure as a service: provides the hardware and usually virtualized OS to their customers - Cloud platform as a service: provides networked computers running in a hosted environment, and adds support for the development environment  cloud software as a service (SaaS). The capability provided to the consumer is to use the provider’s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, except for limited user specific application configuration settings.  cloud platform as a service (PaaS). The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider.  cloud infrastructure as a service (IaaS). The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer can deploy and run arbitrary software, which can include operating systems and applications.  Several online services currently lease storage infrastructure. These storage clouds let anyone with a credit card purchase storage capacity online, paying a monthly fee for the storage they use. 15 TOPIC 8 Algorithm: a finite sequence of unambiguous, executable steps or instruction which terminate and give the solution of the problem. Algorithms are usually written in a pseudocode and later translated to a real programming language. Almost every program involves the steps of input, processing, and output. An algorithm can be written or described or represented using several tools: - Flowchart: Use standardized symbol to show the steps the computer needs to take to accomplish the program’s objective. Because flowcharts are cumbersome to revise, they have fallen out of favor by professional programmers. Pseudo code, on the other hand, has gained increasing acceptance - Pseudo code: Use English‐like phrases to describe the processing process. It is not standardized since every programmer has his or her own way of planning the algorithm Why algorithm important  Describe the steps needed to perform a computation. Important for writing efficient code: execute faster → Time efficiency; Uses less memory → Space efficiency Insertion sort algorithm: It has one of the simplest implementations. It is efficient for smaller data sets, but very inefficient for larger lists. Insertion Sort is adaptive, that means it reduces its total number of steps if given a partially sorted list, hence it increases its efficiency. It is Stable, as it does not change the relative order of elements with equal keys  from algorithm to program: steps - Problem definition: finding the area of a rectangle definition: area=length*width; needed: length and width as real type. - Model development: mathematical model: area= length*width - Algorithm design: (flowchart symbol) - PROGRAM STEPS: writing program, compile, syntax err, executable code  run, output err Computer Programs are simply algorithms that are implemented in a particular programming language like java, JavaScript, HTML, C, python, etc.  A computer program is a set of detailed, step-by-step instructions that tell a computer how to solve a problem or carry out a task. The instructions that make up a computer program are sometimes referred to as code. Programs are written in Programming Languages (PL) A programming language is: A special purpose and limited language, A set of rules and symbols used to construct a computer program, A language used to interact with the computer. A few important characteristics that a computer program should possess are as follows: - Portability: Portability refers to the ability of an application to run on different platforms (operating systems) with or without minimal changes - Readability: The program should be written in such a way that it makes other programmers or users to follow the logic of the program without much effort - Efficiency: Every program requires certain processing time and memory to process the instructions and data 16 - Structural: To develop a program, the task must be broken down into a number of subtasks, so it becomes more readable - Flexibility: A program should be flexible enough to handle most of the changes without having to rewrite the entire program - Generality: means that if a program is developed for a particular task, then it should also be used for all similar tasks of the same domain Programming languages fall into three broad categories: - Machine languages: Uses binary code, Machine-dependent, Not portable - Assembly languages: Uses mnemonics, Machine-dependent, Not usually portable - Higher-level languages (HLL): Uses English-like language, Machine independent, Portable (but must be compiled for different platforms) (Examples: Pascal, C, C++, Java) Machine language: The representation of a computer program which is read and understood by the computer. A program in machine code consists of a sequence of machine instructions. Machine instructions are in binary code Instructions specify operations and memory cells involved in the operation. Assembly languages: A symbolic representation of the machine language of a specific processor. Is converted to machine code by an assembler. Usually, each line of assembly code produces one machine instruction (One-to-one correspondence). Programming in assembly language is slow and error-prone but is more efficient in terms of hardware performance Higher-level languages (HLL): A programming language which use statements consisting of English-like keywords such as "FOR", "PRINT" or “IF“, ... etc. Each statement corresponds to several machine language instructions. Much easier to program than in assembly language. Data are referenced using descriptive names.  TRANSLATING A HIGH-LEVEL LANGUAGE PROGRAM: - Step 1: translate the program written in a high-level programming language into an equivalent program written in assembler programming language through Compiler  CompilersA program that converts another program from some source language (high-level programming language) to machine language (binary numbers) Is distinguished from an assembler by the fact that each input statement, in general, correspond to more than one machine instruction: Source program: The form in which a computer program, written in some formal programming language, is written by the programmer, Can be compiled automatically into object code or machine code or executed by an interpreter. Object program: Output from the compiler, Equivalent machine language translation of the source program. Executable program: Output from linker/loader, Machine language program linked with necessary libraries & other files - Step 2: use an Assembler to translate the assembler language program into machine code  Assembler Assembly language is converted into executable machine code by a utility program referred to as an assembler. An assembler creates object code by translating assembly language instructions into operation codes (opcode). Mnemonics are used to specify an opcode that represents a complete and operational machine language instruction. This is later translated by the assembler to generate the object code. The major fields are: Opcode field which stands for operation code, and it specifies the operation that is to be performed, Operands fields which specify where to get the source and destination operands for the operation specified by the opcode  Program Errors Syntax Errors: Errors in grammar of the language; Runtime error: When there are no syntax errors, but the program can’t complete execution, Divide by zero, Invalid input data; Logical errors: The program completes execution, but delivers incorrect results, Incorrect usage of parentheses 17 i) Problem: Related to user’s task. Produces information need. Information need for the same problem may change, evolve, shift during the IR process adjustment in searching ii) Representation: Converting a concept to query. What we search for. These are stemmed and corrected using dictionary. Focus toward a good result. Subject to feedback changes iii) Query: The process of translating the information need into a query is called as query formulation. A query consists of keywords, and the documents containing those keywords are searched for. A query may consist of a single word or a combination of words with multiple operations. Queries are formal statements of information needs, for example, search strings in web search engines. In information retrieval, a query does not uniquely identify a single object in the collection. Instead, several objects may match the query. 3. Searching/retrieval system  document i) Matching: The query representation is further matched with the document representation that is stored in the index file and is referred to as the matching process. It results in a set of ordered documents based on the relevance and is referred to as the ranked list. ii) Retrieved objects: various order of output, Various forms of output. When citations only: possible links to document delivery. Base for relevance, utility evaluation by users. Relevance feedback, What a user (or you) sees, gets, judges – can be specified How google search works 3 relevant parts: - Crawling & Indexing →Crawl the web and Index the data to allow for efficient searches for keywords or phrases - Algorithms →Rate the importance of each page in the database - Results → Return results in descending order of importance with respect to search  crawling & indexing: Google tries to determine the highest quality results • The "best" results have many factors, including things such as the user's location, language, device (desktop or phone), and previous queries  algorithms: Algorithms are computer programs that look for clues to give you back exactly what you want. Algorithms are the computer processes and formulas that take your questions and turn them into answers  results: All the retrieved results are shown to user. This is most complicated step, but also the most relevant to users. The retrieved results are shown as per the relevancy, site quality and number of matching keyword in results: so more relevant web page link will be displayed first  A Search Engine Results Page (SERP) is the page displayed by a search engine in response to a query by a searcher There exist 2 type: - Paid search results are basically advertisements: the website owners have paid to have their web pages display for certain keywords, so these listings show up when someone runs a search query containing those keywords. This is how SEM work. - Organic search results are the web page listings that most closely match the user’s search query based on relevance. Also called “natural” search results, ranking high in the organic results is what SEO is all about Why is internet marketing important? It gives the company the ability to: drive high quality customers to their websites, increase sales leads from customers looking for their products and services, build their brand online by communicating marketing messages to their target audience, increase their profile against their competitors, target a global audience via international search engines, be accountable with ROI tracking (SEM). Online Media Can be Purchased Using Various Cost Methods: 20 - CPC (Cost per Click): This is the most common tool because it is very popular among advertisers. This is a matter of per click payment. There is no point in impression in this too. CPC means you will get a per click payment or how much the advertiser has to pay to the publisher when they click on their ad banner. Cost per click depends on rate keywords and its success rate - CTR (Click Through Rate): CTR measures the effectiveness of any advertisement, this means that CTR sees how many impressions were on your website or how many users viewed the ad banner and how many people clicked it. So, this is the percentage of the people who clicked the ad banner - CPA (Cost per Action): This is an online advertising pricing model in which the advertiser pays for each specific action such as a form submit, newsletter sign up, filling up inquiry form, registration or any sale. This is a method that gives perfect information about the efficiency of your online ad. This is done whenever a user engages in a defined activity 21 22