Chapter 5 Notes

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Chapter 5 Input Output Device Manager A computer is a machine for constructing mappings from input to output. – Michael Kirby 1 Michael Kirby cannot be ignored here. Most applications do not do much processing of information. It is all about moving information around. The computer takes in input, moves it, makes it pretty, and then outputs it in another form. As I type this section, I am inputting words through a keyboard, with an occasional adjustment using the mouse, and seeing them on the monitor in the correct place. In between the computer captures the input, stores it in one or more locations applies a simple algorithm to interpret the results and sends it to the graphics port for display. That seems pretty simple. It is not and that is what I will cover in this chapter. Learning Objectives After completion of this chapter, you should be able to: 1. Discuss the importance of input and output to computers. 2. Summarize key concepts of Input and Output devices on computers. 3. Describe the critical components of the input and output devices and how they interact. 4. Discuss problems with input and output and how it can affect a computer 5. Discuss techniques used to implement input and output. 6. Analyze performance implications of various input and output buffering alternatives. Survey Your Thoughts What are the most important input and output devices on your computer? Input a. Bar Code Reader b. Joystick c. Keyboard d. Light pen e. Microphone 1 From https://www.wisefamousquotes.com/quotes-about-input-output downloaded on 6/15/21 1
Chapter 5 Input Output Device Manager 2 f. Mouse g. Scanner h. Touch screen i. Track ball Output a. GPS b. Headphones c. Monitor d. Printer e. Projector f. Sound Card g. Speakers h. Video Card
3 Chapter 5 Input Output Device Manager Important is one of those funny words you come across all the time in this industry. You should be asking questions like important to whom or important for what. Knowing what you are doing will drive what is and what is not important. Getting back to this survey. Most common output device would be some type of video display. Most computers are geared to a visual environment so having a video display is common. For input the most common would be some type of text entry device, such as a keyboard. Though a pointing device is up there as well. This part of an Operating System (see Figure 1) is usually either ignored or given only cursory coverage in most Operating System text books. And the reason is clear, in the past most of the software and all of the hardware was considered outside the Operating System. Only a few configuration files were managed by the Operating System. And in the early days of desktop systems (1980s) most of the problems with the computer system came down to input or output issues. These included conflicting interrupts, drivers loaded in the wrong location, improper memory space allocation for the device, and—the big one—an updated driver that doesn’t work with some device. This is where Information Technology professionals spent their time. And many of these were intermittent issues so tracking them down took loads of time. Today the systems have more stability, and we are working with a different construct for organization (I will get to that in this chapter), but the issue of input and output did not disappear from our work. Figure 1 The Input Output Device Manager Alt Tag. Operating System Notational Diagram highlighting the Input Output Device Manager and Input Output hardware. In this chapter I will discuss how input and output operates and how it is managed by the Operating System. I will go into detail about the mechanisms used and the storage structures set up to make all these parts function together. As in other chapters some of this is specific to what
Chapter 5 Input Output Device Manager 4 Information Technologists do, but all of it will go into topics that may be applied to other aspects of your work. I will discuss: Overview of Input and Output—why we have input and output, the challenges input and output afford the Operating System and the computer, the objectives for input and output and how it all fits. Input and Output Features—the wide range of devices out there and the challenges that presents to the system and everything connects to each other. Operating System Organization—what hardware and software is needed and how it is organized. Support Structures—what commands are used and information is stored Communication with Input and Output—how commands get from the microprocessor to the individual devices. Technology to Improve Input and Output—techniques that make input and output more efficient or effective or both. Section 5.1 Overview of Input and Output Input and Output (I/O) consists of the physical devices, the connections, the support equipment, and the software that interprets the machine’s commands into the intricacies that direct and monitor the individual devices. In most computers, input and output takes up the majority of space. For example, Figure 2 shows a middle of the road motherboard for a desktop system. At the time of purchase this motherboard went for about $200 on the retail market. I will use this motherboard throughout this chapter to discuss concepts. Notice that only one small (well relatively small compared to the board as the microprocessor chip is about 2 inches on a side) area is devoted to the CPU and the rest of the board is for input and output. This board takes up about 10% of the space in an enclosure (a fancy name for a box—but it is the industry term). The enclosure also houses the power supply, a box about 5 x 8 x 3 inches, and a few fans to keep everything cool. The rest is devoted to input or output.
5 Chapter 5 Input Output Device Manager Figure 2 ASRock Z270 Extreme Motherboard Alt Tag. Component side of the ASRock Z270 Extreme Motherboard 5.1.1 Why have Input and Output The computer does nothing without input and output. Without input the computer can only execute a program that does the same thing—repeatedly. Input changes the nature of the program. Even a simple calculator cannot perform a calculation without input. Sure, we can write a program to add the numbers 2 and 3, but once you get 5 the first time, what is the point. Why spend all that time and money to write a program to do just that. Just get a piece of paper and write the number 5. With input I can make the calculator do any manner of calculation and get different, unique, results as my need calls upon them. With output I can actually see what I am doing. Thus, the CPU needs data. This data comes from the outside world. To get it into the CPU we need input devices. To see the results, we need output devices. The most basic personal computer has a keyboard, storage device, and a display. One of the simplest systems ever built was the Commodore VIC-20. It came with a keyboard, an Rf 2 coupler, a cassette tape drive, and wires. The keyboard was a box that contained the power supply and CPU. You connected the Rf coupler to the keyboard with a wire and to your television antenna terminal with another wire, the cassette tape drive connected to the keyboard with a wire, then you plugged the Keyboard into a home outlet and turned the ON/OFF switch to the ON position. Then dialed your television into the channel listed on the Rf coupler. This usually got you an error telling you to load the proper cassette tape into the drive and you started again. To give you a feel for this system, it was a $300 computer (then-year dollars, that would be about $800 today) using a 6502 microprocessor (8-bit CPU) that was capable of addressing 32kB of main memory. It came with 20 kB of ROM and 5 kB RAM. It came out in 1980 in an attempt to capture the home market. Prior to that, Commodore’s earlier system (1977), the Commodore Pet was a single box machine with keyboard, display, and cassette tape drive all in one. The monitor drove the price out of the home market. The Apple II and Radio Shack’s TRS-80 had similar set ups. Thought Question: List all the computer input devices you can think of? ble 1 shows a brief list of input devices. 2 Rf for Radio Frequency. As in a television channel.
Chapter 5 Input Output Device Manager 6 Table 1 Input Devices 10-key device Joystick Punched Card Reader 3D Scanner Keyboard Pyrometer Barcode Ready Kinect Sensor Scanner Camera Media Player Tachometer Digital Pen Microphone Touch pad Gamepad Mouse Touch screen Humidistat Paddle Trackball Jog Dial Pointing Stick Tracker Thought Question: List all the computer output devices you can think of? Table 2 shows a brief list of output devices. Table 2 Output Devices Actuator 3 Printer Speakers Monitor Punched Cards Thought Question: List all the computer devices missing from your input and output list? 3 This one is lumped and anything that does something is an actuator. Thus, anti-lock brakes and a machine shop lathe are both considered actuators.
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