Computer Science Notes PDF

# Computer Science ### Chapter 1 * **Computer Science:** A science specializing in the study of computers and computational systems. * **Computer:** A Computer is an electronic device that accepts data, performs computations, and makes logical decisions according to instructions that have been gi...

# Computer Science ### Chapter 1 * **Computer Science:** A science specializing in the study of computers and computational systems. * **Computer:** A Computer is an electronic device that accepts data, performs computations, and makes logical decisions according to instructions that have been given to it. ### Characteristics of Computers: * **Speed** * **Accuracy** * **Storage** * **Diligence** * **Power of remembering** * **No IQ** * **Versatility** * **No feeling** ### Types of Computers 1. **Classification by the method of operation:** * **Analog Computers** * **Digital Computers** * **Hybrid Computers** 2. **Classification by purpose of application:** * **Special purpose computers** * **General purpose Computers** 3. **Classification by physical size, capacity, and performance:** * **Super Computers** * **Mainframe Computers** * **Mini Computers** * **Micro Computers** ### **Chapter 3** * **Software engineering:** It is concerned about the development of a better quality Software by applying scientific and basic engineering principles. * **Computer Networks:** It is concerned with connecting Computers for the purpose of sharing resources. * **Database Systems:** Involves the study and design of efficient methods for information storage, process and retrieval. * **Artificial Intelligence:** It is concerned with the means by which computers can perform tasks that would be characterized as intelligent if performed by human beings. ### Chapter 4 * **Computer system components:** 1. **Input device:** Users interact with a Computer using input devices (mouse and Keyboard) to provide instructions to a computer. 2. **Output device:** Computer user uses a screen or monitor or printer to display outputs outputs. 3. **Central processing unit (CPU):** The brain of the Computer, this is the component responsible for executing instructions. * **Information Technology:** The study or use of systems for storing, retrieving, and sending information. * **DBMS** — Data Base Management Systems ### Chapter 5 * **Information and Communication Technology (ICT):** Is an umbrella term that includes communication device or application for processing and communicating information. ### Computer Science 1. **Software** is the science that studies the intangible components - ex programs. 2. **Hardware:** Is the science that studies the tangible parts - ex Computer Components ### Chapter 2 * **Memory:** The computer's workspace where application instructions and data are held during operation. * **Known as** - Main memory - Primary storage - RAM * **RAM** Random Access Memory * The capacity of a memory is important. Bigger memory means bigger Workspace..... ### Types of Memory * **Volatile** * **RAM** * **DRAM** * **SRAM** * **Non-Volatile:** * **ROM** * **PROM** * **EPROM** * **EEPROM** * **Flash Memory** ### Chapter 7 * **RAM** → Random Access Memory * **DRAM** → Dynamic random access memory * **SRAM** → Static random access memory * **ROM** → Read only Memory * **PROM** → Programmable Read only memory * **EPROM** → Erasable programmable read only Memory * **EEPROM** → Electrically Erasable programmable read only Memory * **Volatile Memory:** Contents are erased when the system's power is turned off or interrupted. ### Chapter 8 * **DRAM** requires the data to be refreshed periodically in order to retain the data. * **SRAM** does not need to be refreshed. * **SRAM** is static while **DRAM** is dynamic. * **SRAM** is faster than **DRAM**. * **SRAM** is more expensive than **DRAM**. * **Input Devices:** Any type of device that provides data to a computer from the outside world. * ex: Keyboard, Mouse, Scanner * **Output Devices:** Any type of device that provides data from a Computer to the outside world. * ex: Monitor, Printer ### Chapter 9 * The most common types of output devices: * **CRT** * **LCD** * **Specifications of output devices:** * **Refresh rate** * **Resolution** * **Visible screen Size** * **Electron gun:** Is a negatively charged Cathode located at the back of the tube * **CRT:** The beam scans across the Monitor from left to right and top to bottom to create or draw the image, line by line. ### Chapter 10 * **How does Video travel from the processor to a CRT/LCD Monitor?** * **Step 1:** The processor sends digital Video data to the video card. * **Step 2:** The video card's digital to analog converter (DAC) Converts the digital Video data to an analog Signal. * **Step 3:** The analog signal is sent through a Cable to the **CRT Monitor**. * **Step 4:** The **CRT** monitor separates the analog signal into red, green, and blue signals. * **Step 5:** Electron guns fire the three color signals to the front of the **CRT**. * **Step 6:** An image is displayed on the screen when the electrons hit phosphor dots on the back of the screen. ### Chapter 11 * **Printers:** Output device that produces text and graphics on paper result is hard copy or printout. * **Main types of printers:** * **Dot Matrix:** Is a printer that uses hammers and a Cibbon to form images out of dots. * **Inkjet:** Are very basic printers with very few moving parts. * **Laser:** Is a printer that uses a Focused beam or light to transfer text and images onto paper. ### Chapter 12 * **The Arithmetic and logic unit (ALU):** Performs Mathematical operations (+, -, ×, ÷) and logic operations (=, >, <, and, or, not, ( ~) * **The ALU is composed of:** * **Circuits** responsible for performing arithmetic/logic operations. * **Registers** responsible for storing intermediate Computational results. * **Bus** that connects the two. * **The control unit:** is responsible for managing the process of moving data and program into and out of memory. * **Peripheral Devices:** Is any device such as Mouse or Keyboard connected to a computer system to add functionality. ### Chapter 13 * **Types of peripheral Devices:** * **Input devices** * **Output devices** * **Secondary storage devices** * **System software** is divided into: * **Operating system** * **Language software** * **Application Software** ### Chapter 14 * **A network:** Consists of a collection of Computers and other hardware connected together. * **Why use Computer Networks?** * **Resource sharing** * **High reliability** * **Cost Saving** * **Enhance online Communications** * **Internet:** A Collection of networks interconnected and function as a single World Wide network. * **URL** → The universal Resource Locator ### Chapter 15 * **Types of Networks** * **Topology** (shape) * Bus * Ring * Star * Mesh * **Architecture** * Client-server * Peer to peer (P2P) * **Size** * LAN * WAN * Man * Pan * Wireless (eg local Area Network) ### Chapter 16 * **Bus Topology** * **Advantages** * Easy to Connect a Computer or device * Requires less cable length than other topologies. * **Disadvantages** * Data must pass through every Computer between sender and receiver - which makes it slower * Entire network shuts down if there is a break in the Main Cable. * Terminators are required at both ends of the Main Cable * Difficult to identify the problem if the entire network shuts down. ### Chapter 17 * **Ring Topology** * **Advantages** * Easy to install and Wire * **Disadvantages** * Data must pass through every computer between sender and receiver which makes it slower * Entire network shuts down if there is a break in the main Cable * Difficult to identify the problem if the entire network shuts down. ### Chapter 18 * **Star Topology** * **Advantages** * Easy to install and wire * Easy to add or remove Computers and devices. * Easy to detect problems. * **Disadvantages** * Requires more cable length than bus topology * If the hub fails, nodes attached are disabled * More expensive than bus topology because of the cost of the hub. * **Mesh Topology** * **Advantages** * No traffic problems. * Privacy and security * **Disadvantages** * More cables required * Expensive Hardware * Difficult installation and configuration. ### Chapter 19 * **Client Server Networks** * **Advantages** * Simple network administration. * More scalable. * Data is stored on the servers (Greater security and easy to update data). * **Disadvantages** * High traffic * Network Failure - clients are helpless * Higher costs. * **Peer to peer (P2P)** * **Advantages** * Easy to install or configure. * Inexpensive. * User is able to control their own resources. * No need for an administrator. * **Disadvantages** * Security problem. * Performance suffers when a computer is accessed. * Централизованное управление данными. ### Chapter 20 * **LAN** → Local Area Network * **WAN** → Wide Area Network * **MAN** → Metropolitan Area Network * **PAN** → Personal Area Network * **Speed** = distance/time * **BW** = Data size/time * **Depends on:** * Media type * Coding of information