Write the mesh-current equations for the circuit in Fig. 3.117.
Chapter 1: Defining Information Technology COMPUTATIONS GREATEST HITS Digitizing information “digital information” “data represented using numbers” the big breakthrough – getting a machine to read digital information Herman Hollerith (statistician) o First “production” application of digital information o Knew that processing census data by hand was slow (8 years) so he invented a machine to tabulate data based on holes punched in cards (1 year) How to Digitize a Punch Card: A punch card is moved toward the left by a metal roller. Above the roller is a bundle of metal wires called a brush. When the hole moves over the roller, the brush pokes through the hole and touches the roller, making an electrical connection. Processing the Information The machine can count the cards using its odometer, which counts cards like a car counts miles Separate the input into the two stacks and then run each stack through the machine again to count them The number of males and females in the input can be determined mechanically No Computer Needed This device ≠ computer It is a card reader and stacker, detecting the presence/absence of a hole in the card By careful application, it can perform information-processing activities o Ex: How many men and women are in a population Stored-Program Computers All Hardware All The Time Tabulating machines = electro-mechanical devices Hardware: built out of wires, rollers and motors To change the operations that the machine performedrewired o More versatile: machines evolved to have plugboards to help “programmers” rewire them. Main Problem: only very simple operations were possible when the “program” was expressed using wires Put the Program in Memory The electronic computer solved the “rewiring” problem by using a special device o The central processing unit-which performs instructions stored in the computer’s memory o Effectively changed instructions, “hard” wires “soft” memory bites. Software o Advantages of Soft Instructions compared to Hard Instructions Programs can be changed rapidly Programs can be much more complex Computations are autonomous – they can run on their own without a person attending to them Big and Expensive Main problem with early computers (CPU part): complexity Difficult technical problem: to build a hardware device that can read, decode, and perform instructions 1 electronic computer: ENIAC Burned Out Another issue: lack of reliability Electronic circuits were built from vacuum tubes An instruction executing CPU required A LOT of them to work all at once, that takes a lot better reliability. 1 or more tubes would fail causing the computer to crash Electronic computer became a powerful “game changing tool” o Reason: transistors The Switch to Transistors 3 Bell Lab Scientists received Nobel Prize for their 1947 invention: semiconductor transistor o John Bardeen o Walter Brattain o William Shockley Transistors – solved MANY problems o Low power, meaning less heat (and streetlight dimming) o Extremely reliable o Small in size and weight o Made computers affordable (to corporations) o Mainly allowed them to have much more complex CPUs Much Assembly Required Building a computer/large electronic system in 1950s/60s was a tedious and time-consuming activity Separate parts had to be assembled Integrated Circuits Solution: Integration o “silicon technology” – Silicon Valley Integration Integrated circuits (ICs) – are monolithic blocks (chips) made of silicon and closely related elements in which both active parts like transistors and connective parts like wires are fabricated together in a multistep process. Photolithography Makes ICs so spectacularly successful Chip makers “print” the wires and all the other parts onto the chip The Genius of Printing To print on a chip, the photolithography process requires a mask to specify the shapes of a layer-it’s like a photographic negative used before digital cameras Doesn’t matter how complex or simple the mask is Progress Computers now are fabricated as chips that can be held between two fingers “Personal” Computers Now fitting more transistors on each chip – known as “Moore’s Law” o A computer of a given capacity needed fewer and fewer chips which made them cheaper and cheaper A Personal Computer st Alto: 1 serious attempt to make a personal machine People said there’s no reason any individual to have a computer in their home but Games, primitive word processing and email attracted enough users to push the develop forward Serious Resistance Adults had a fear of using the computers More successful with younger users which began a generational gap The Internet APRANet o Key idea: to allow these separate networks to connect together only if they both used a common communication protocol called TCP/IP o Internet (a network of networks) was born o “dial-up method” - slow and fuzzy. Today – broadband o HTTP and the World Wide Web Idea: was to create an online center where everyone could access the documents, images, and other resources and other resources of CERN, the agency for whom Bernes-Lee worked HTTP protocol = universal o Your browser (the client) and the host (the Web server) know exactly how to interact: what’s requested and what will be returned, and how, and in what format o TCP/IP is essential Mosaic: first widely used Web Browser o Firefox: grandchild of Mosaic Layered Software Development Prior to 1980s: programs were monolithic with little structure, difficult to write and impossible to maintain After 1980s: software development has steadily matured becoming more disciplined and sophisticated Software development applies a layered approach in which programs at one level apply code for the more primitive operations from lower levels, and provide more advanced facilities for higher levels An Accumulation of Knowledge Programmers can use the software in these boxes without ever understanding how those programs work, beyond knowing the proper way to use them. They are building on the work of thousands of other programmers, who have contributed to these layers As technology advances, more boxes will be included ad more layers will be added. Software gets more and more complex, and more and more sophisticated based on the combined efforts of many programmers. We build on what we can already do The Great Part of the Greatest Hits Reducing the impact of complexity has often been a key result of these discoveries o The CPU and soft instructions allowed a machine to do more complex computations, and to accomplish them autonomously o Integration and photolithography all but eliminated the complexity of building electronic devices o Layered software development allows programmers to build on the work of thousands of others without the need to understand the operation of their computations-only how to use them. Others will build on their work TERMS OF ENDEARMENT Tech Support You have to use the right words and computer terms so they know what you are talking about It will be amazingly effective and get your issue solved faster Anchoring Knowledge Learning the computer terminology and look out for it and understand it COMPUTERS, SOFTWARE, ALGORITHMS Find the Computer Computers become smaller and cheaper Most people already own many computers Processors Computers are everywhere o Embedded as components of phones, the Wii, microwave ovens, music players, brakes, etc Computer’s more technical name: processors Processor: includes the CPU, a small amount of memory usually called a cache, and is connected to some input and/or output devices. o The main variation comes with the devices the computer is connected to, and of course, the software ARMs Race ARM: a processor specialized to be part of other systems, though it’s found everywhere these days Advanced RISC Machine o RISC: Reduced Instruction-Set Computer Software Software: a collective term for programs, the instructions computers perform to implement applications o “instructs” the computer hardware by providing the steps needed to perform a task, say, to display a Web page or play a game o the computer, using the CPU, follows the program and carries out the instructions extremely rapidly and with great accuracy o Specifying what to do is the point of greatest leverage Programing: “instructing an agent to perform some function or action” by giving a step-by-step process Agent: anything that can follow the instructions Algorithms Algorithm: a precise and systematic method for producing a specified result For a process to be an algorithm it must have these 5 properties o Specifying input o Specifying output Means to say what the computation is given as data, and what it will produce as a result o Definite The whole process is spelled out unambiguously o Effective It is within the “abilities” of the agent following the instructions o Finite The agent will eventually finish the computation, giving the right answer, or stop and report that none is possible THE WORDS FOR IDEAS “Abstract” Abstract: to remove the basic concept, idea, or process from a situation o The removed concept is usually expressed in another, more succinct and usually more general form, called an abstraction Noticing 2 points o Many but not all of the details of the story are irrelevant to the concept o The idea-the abstraction-has meaning beyond the story In computing, separating the relevant from the irrelevant, and applying the abstraction to other cases, are both essential “Generalize” To express an idea, concept or process that applies to many situations Idea generalization “Operationally Attuned” To apply what we know about how a device or system works to simplify its use “Mnemonic” A rather unusual term that we use in IT Is an aid for remembering something Lecture Notes What is information technology Utlizing that data for business environment Why do I need to know about it Every business uses computers -input & output data -manipulate data -store a program How we do Business today -Cloud services -Data analysis -World Wide Web -Social Media -Video Games Data -Digitalizing information Data represented numbers The breakthrough Machines reading digital info Census data digitalized (1890) 1880 it took 8 years to process the data by hand Punch cards digitalized the process Fully mechanical All Hardware PC - hardware and software From vacuum tubes, transistors, integrated circuits It gave off a lot of heat 30 tons Hardware -Keyboard -Mouse Output -Monitor -Printer The software stack -you don’t need every single part Every programmer doesn’t have to know every piece Specialize in a certain type of program, application, hardware drivers, to the monitor If one piece stops working, you can still use the computer but you wont be able to do the certain action User: User mode, applications S/W Stack: kernel mode drivers, OS IO Manager, File System, Volume Manager, Disk Class Driver, Minipot Driver Cache Manager H/W: Hardware Drivers, Host Bus, HBA Cache System recovery Software Stack -To check out a vid on YB using a phone you would: Use the browser application to get to YouTube Use the browser app uses the window manager and several other frameworks Abstraction To remove the basic concept idea or process from a situation -abstraction helps hiding complexity -details that are irrevelant for understanding from a special point of view are ignored Abstraction focuses upon the essential concepts Algorithms: a precise and systematic method for producing a specified result or solve a problem The underlying goal is to find the best possible way to do something effectively and efficiently. Not all algorithms are inherently efficient nor effective A slow but SMART computer might be able to do something faster than a faster but NOT SO SMART, one. This smartness is the algorithm, hence, the process to be used to solve a problem Algorithm is not a program