Balanced Introduction to Computer Science, Slides of Computer Science

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A Balanced Introduction to Computer Science Computer Basics Docsity.com What is a Computer? •a computer is a device that receives, stores, and processes information •different types of computers have different characteristics – supercomputers: powerful but expensive; used for complex computations (e.g., weather forecasting, engineering design and modeling) – desktop computers: less powerful but affordable; used for a variety of user applications (e.g., email, Web browsing, document processing) – laptop computers: similar functionality to desktops, but mobile – palmtop computers: portable, but limited applications and screen size Docsity.com Common Desktop Hardware System unit—contains CPU, RAM (main memory), and other supporting components Screen (output device) CD-ROM drive (secondary memory) Hard-disk drive (secondary memory) Speakers (output device) =e _ mmm Keyboard (input device) | Baie aa A aia ®: Mouse (input device) Docsity.com von Neumann Architecture • although specific components may vary, virtually all modern computers have the same underlying structure – known as the von Neumann architecture – named after computer pioneer, John von Neumann, who popularized the design in the early 1950's • the von Neumann architecture identifies 3 essential components 1. Input/Output Devices (I/O) allow the user to interact with the computer 2. Memory stores information to be processed as well as programs (instructions specifying the steps necessary to complete specific tasks) 3. Central Processing Unit (CPU) carries out the instructions to process information Docsity.com Central Processing Unit (CPU) •the CPU is the "brains" of the computer, responsible for controlling its inner workings – made of circuitry – electronic components wired together to control the flow of electrical signals – the circuitry is embedded in a small silicon chip, 1-2 inches square – despite its small size, the CPU is the most complex part of a computer (CPU circuitry can have 100's of millions of individual components) – commercial examples: Intel Core 2 Duo, Intel i5, AMD Sempron, AMD Athlon Docsity.com Memory (cont.) • memory capacity is usually specified in bytes – a byte is a collection of 8 bits – so can represent a range of 28 = 256 values – large collections of bytes can be specified using prefixes since a byte is sufficient to represent a single character, can think of memory in terms of text  a kilobyte can store a few paragraphs (roughly 1 thousand characters)  a megabyte can store a book (roughly 1 million characters)  a gigabyte can store a small library (roughly 1 billion characters)  a terabyte can store a book repository (roughly 1 trillion characters) Docsity.com Memory (cont.) •modern computers use a combination of memory types, each with its own performance and cost characteristics •main memory (or primary memory) is fast and expensive – data is stored as electric signals in circuitry, used to store active data – memory is volatile – data is lost when the computer is turned off – examples: Random Access Memory (RAM), cache •secondary memory is slower but cheaper – use different technologies (magnetic signals on hard disk, reflective spots on CD) – memory is permanent – useful for storing long-term data – examples: hard disk, flash drive, compact disk (CD) Docsity.com Memory (cont.) • higher-end computers tend to have – more main memory to allow for quick access to more data and programs – more secondary memory to allow for storing more long-term data Docsity.com Operating Systems •the Operating System (OS) is a collection of programs that controls how the CPU, memory, and I/O devices work together – kernel: manages the CPU's operations, controls how data and instructions are loaded and executed by the CPU, coordinates other hardware components – file system: organizes and manages files and directories – graphical user interface (GUI): provides intuitive, visual elements for interacting with the computer • GUI's utilize windows, icons, menus, and pointers Docsity.com Quick Net & Web Overview • the Internet is a vast, international network of computers – the physical connections between computers vary, but the overall effect is that computers around the world can communicate and share resources – the Internet traces its roots back to 1969, when the U.S. government sponsored the first long- distance computer network – starting with only 4 computers, the network would eventually evolve into today's Internet the World Wide Web is a collection of software that spans the Internet and enables the interlinking of documents and resources  the basic idea for the Web was proposed by Tim Berners-Lee in 1989  his system interlinked documents (including multimedia elements such as images and sound clips) over the Internet  through the use of well-defined rules, or protocols, that define how they are formatted, documents could be shared across networks on various types of computers Docsity.com Internet ≠ World Wide Web •the Internet could exist without the Web – and did, in fact, for many years (applications included email and news groups) •the Web couldn't exist without the Internet – the Internet is the hardware that stores and executes the Web software Docsity.com