History and Types of Computers

Definition of Computers

• Computers are programmable devices that process, store, and retrieve data, allowing global connectivity and transformative impact on the world.

History of Computers

• The term "computer" originally referred to a person performing manual calculations.
• Early computers used vacuum tubes, making them large and limited in computing power.
• Transistors replaced vacuum tubes in the second generation, significantly reducing size, cost, and power consumption.
• Integrated circuits (ICs), invented by Jack Kilby, allowed for smaller, cheaper computers.
• Microprocessors, like the Intel P4004, integrated CPU, memory and I/O controls onto a single chip.

Types of Computers

• Digital computers operate data sequentially in binary (0 and 1), each digit represented by a transistor.
• Analog computers use physical quantities like voltage for calculations, mirroring the properties of the data.
• Analog data is prone to noise, making digital data more reliable.

Pioneers in Analog Computing

• James Thomson created early analog computing devices, including a wheel and disc integrator.
• Lord Kelvin collaborated with Thomson on a device for integrating functions and designed a tide-predicting machine.
• Vannevar Bush developed the Differential Analyzer, a general-purpose analog computer.

Generations of Digital Computers

• First Generation (Vacuum Tubes): Used thousands of vacuum tubes, bulky, with examples like the Atanasoff-Berry Computer (ABC), Colossus, ENIAC, UNIVAC I, and IBM 701.
• Second Generation (Transistors): Transistors replaced vacuum tubes, significantly reducing size, cost, and power consumption.
• Third Generation (Integrated Circuits): ICs allowed smaller, cheaper computers with keyboards, monitors, and operating systems for multi-application processing.
• Fourth Generation (Microprocessors): Microprocessors reduced computer sizes to fit in the palm of the hand.

Components of Computers

• Input Unit: Takes user commands in data format and converts them to digital language for processing.
• Central Processing Unit (CPU): Executes instructions and processes data.
• Memory Unit: Stores data and instructions, using bits and bytes to measure data size.
• Control Unit: Manages data flow, directs system functions, and converts data into machine language.
• Arithmetic-Logical Unit (ALU): Handles mathematical operations and data comparisons.
• Output Unit: Displays processed data (e.g., monitors, printers).

Operating Systems

• Definition: Software that makes computer hardware usable, managing system performance and resources for users.
• Examples: Microsoft Windows, Mac OS, Google Android, Apple iOS.
• Advantages: Abstraction, Executable Programs, User-Friendly Interface.
• Disadvantages: Volatility, Cost, Security.

The Power of the Web and the Internet

• Web (World Wide Web): A system of interconnected web pages linked via hypertext and hypermedia.
• Internet: A network infrastructure connecting millions of computers globally, facilitating data communication.

History of the Web

• Tim Berners-Lee: Developed the WWW in 1989 at CERN using hypertext.
• First Website: Launched August 6, 1991, introducing hypertext and web servers.
• Expansion: NCSA released browsers compatible with PCs and Macs, leading to widespread adoption by 1993.

Brief History of the Internet

• 1960s: J.C.R. Licklider conceptualized a global network; packet-switching led to ARPANET.
• 1980s: PhoneNet and Telenet connected ARPANET and Telenet, broadening email access globally.
• 1990s: ARPANET decommissioned; the internet expanded to the public sector.
• 1990s: Tim Berners-Lee developed HTML and URLs, leading to the first website.
• 1990s: Windows 95 popularized the internet, with companies like Amazon and Yahoo emerging.
• 2000s: The Dot-Com Bubble led to heavy investment in internet startups, followed by a crash in 2001.
• 2000s: Google emerged as a top search engine; Wi-Fi and mobile internet access surged.

How the Web and the Internet Changed the World

• Communication: Revolutionized global communication via email and social media but increased impulsive messaging risks.
• Information Access: Search engines and e-books made knowledge widely accessible, but misinformation is a concern.
• Entertainment: Social media, online gaming, and streaming services have transformed entertainment but can negatively impact social connections.
• Education: The internet enabled online learning during COVID-19 but students risk reliance on digital learning environments.

Domain Name System (DNS)

• Created by Paul Mockapetris, Jon Postel, and Craig Partridge, symbolics.com was the first registered domain in 1984.