Introduction to Computers - I/O Devices PDF

Introduction to Computers Chapter No 2 I/O Devices and Peripherials ITC - Chapter 2 I/O Devices and Peripherials 1 : What Computers Do ? Four basic functions of computers include: – Receive input – Process inf...

Introduction to Computers Chapter No 2 I/O Devices and Peripherials ITC - Chapter 2 I/O Devices and Peripherials 1 : What Computers Do ? Four basic functions of computers include: – Receive input – Process information – Produce output – Store information 1  Input and Output Hardware ? Input Hardware ?Consists of devices that translate data into a form the computer can process. ? Output Hardware ?Consists of devices that translate information processed by the computer into the form that humans can understand Input Devices Computers accept information from the outside world. The keyboard is the most common input device. Pointing devices like the mouse also provide input. 2 Process Information The processor, or central processing unit (CPU), processes information, and performs all the necessary arithmetic calculations. CPU is like the “brain” of the computer. Output Devices Computers produce information and send it to the outside world. A video monitor is a common output device. Printers also produce output. 3  Store Information Memory and storage devices are used to store information. Primary storage is the computer’s main memory. Secondary storage uses disks or other media. Primary storage Secondary storage Computer’s Core: The CPU and Memory The transformations are performed by the CPU - the central processing unit or processor. The microprocessor, which is a silicon chip, is located on the motherboard. 4  Computer’s Core: The CPU and Memory When you purchase a computer, the selection of the CPU is a very important choice. There are two factors that are very important to computer users are: – Compatibility – Speed Compatibility Not all software is compatible with any given CPU. Each computer has a unique instruction set - a vocabulary of instructions the processor can execute. New microprocessors can usually run older software, but new software is not usually compatible with old microprocessors. 5  Speed The computer’s speed is measured by the speed of its internal clock - a device to synchronize the electric pulses. Speed is measured in units called megahertz (mHz). Primary Storage: The Computer’s Memory RAM ( Random Access Memory): – RAM is the most common type of primary storage, or computer memory. – used to store program instructions and data temporarily – unique addresses and can store in any location – can quickly retrieve information – will not remain if power goes off (volatile). 6  Primary Storage: The Computer’s Memory ROM ( Read-Only Memory): – information is stored permanently on a chip. – contains startup instructions and other permanent data. Buses, Ports, and Peripherals Information travels between components through groups of wires called Buses. 7  Buses, Ports, and Peripherals Peripherals are external devices for receiving input or producing output. Example (keyboard, monitor, and mouse). Communicate with other parts of the system. Buses, Ports, and Peripherals Ports provide attachment and communication with external devices by means of: Slots ( For internal attachments ) Ports ( For external attachments ) 8  The Keyboard A standard computer keyboard has about 100 keys. Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters. The Omnipresent Keyboard ? Do you know where these keys are located on the keyboard and how to use them? ? Letters, Numbers, Cursor Keys, Delete Key, Enter (Return) Key, and Function Keys 9  Standard Keyboard Layout Most keyboards have keys arranged in five groups: – Alphanumeric keys – Numeric keypad – Function keys – Modifier keys – Cursor-movement keys Standard Keyboard Layout 10  Working of Keyboard Pointing Devices Mouse Joystick Touch Screen Graphics Tablet 11  Mouse The mouse is a pointing device. You use it to move a graphical pointer on the screen. The mouse can be used to issue commands, draw, and perform other types of input tasks. Mouse Techniques Using the mouse involves five techniques: – Pointing; Move the mouse to move the on-screen pointer. – Clicking Press and release the left mouse button once. – Right-clicking Press and release the right mouse button. – Double-clicking Press and release the left mouse button twice. – Dragging Hold down the left mouse button as you move the pointer. 12  Other Pointing Devices Trackballs: – A trackball is like a mouse turned upside- down. Use your thumb to move the exposed ball and your fingers to press the buttons. Touchpads or Trackpads A touchpad is a touch-sensitive pad that provides the same functionality as a mouse. – To use a touchpad, you glide your finger across its surface. – Touchpads provide a set of buttons that function like mouse buttons. 13  Joystick It is also a pointing device. It consists of a vertical handle like a gearshift lever mounted on a base with one or two buttons. They are primarily used for playing games. Joysticks are popular for flight simulator and driving games. Alternative Input Devices Light Pens Pen-based Systems Touch Screens Digitizing Tablets 14  Pen-based System With a pen-based system, you use an electronic pen to write on the screen and choose commands. Pens are common input devices for handheld computers, like “personal digital assistants (PDAs).” Pens are handy for making notes or selecting commands, not for inputting a lot of text. Pen-based System The user can point, tap, draw and write on the computer’s screen with a pen 15  Touch Screens Touch-screen systems accept input directly through the monitor. Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse. Touch-screen systems are useful for selecting options from menus. Touch Screens 16  Digitizing Tablets An input device that enables you to enter drawings and sketches into a computer. A digitizing tablet consists of an electronic tablet and a cursor or pen. A cursor (also called a puck) is similar to a mouse, except that it has a window with cross hairs for pinpoint placement, and it can have as many as 16 buttons. A pen (also called a stylus) looks like a simple ballpoint pen but uses an electronic head instead of ink. Source-Data Entry Does not require keystrokes Direct entry into computer often is more accurate Main devices – Bar-code readers – Mark and character recognition devices – FAX machines – Imaging systems 17  Bar-Code Vertical striped marks on most manufactured products Often seen is a Universal Product Code, as seen in North America and Australia Photoelectric scanners that translate code symbols into digital code The reader emits light, which reflects off the bar code and into a detector in the reader. The detector translates the code into numbers. Flatbed bar code readers are commonly found in supermarkets. Courier services often use handheld readers. Bar-Code Bar code readers commonly track sales in retail stores 18  Bar-Code "UPC" stands for Universal Product Code. UPC bar codes were originally created to help grocery stores speed up the checkout process and keep better track of inventory, but the system quickly spread to all other retail products because it was so successful. UPCs originate with a company called the Uniform Code Council (UCC). A manufacturer applies to the UCC for permission to enter the UPC system. The manufacturer pays an annual fee for the privilege. In return, the UCC issues the manufacturer a six-digit manufacturer identification number and provides guidelines on how to use it. You can see that the UPC symbol printed on a package has two parts: The machine-readable bar code The human-readable 12-digit UPC number 19  Bar-Code: UPC Manufacturer identification number is the first six digits of the UPC number -- 639382. The next five digits -- 00039 -- are the item number. A person employed by the manufacturer, called the UPC coordinator, is responsible for assigning item numbers to products, making sure the same code is not used on more than one product, retiring codes as products are removed from the product line, etc. In general, every item the manufacturer sells, as well as every size package and every repackaging of the item, needs a different item code. So a 12-ounce can of Coke needs a different item number than a 16-ounce bottle of Coke, as does a 6-pack of 12-ounce cans, a 12-pack, a 24-can case, and so on. It is the job of the UPC coordinator to keep all of these numbers straight! The last digit of the UPC code is called a check digit. This digit lets the scanner determine if it scanned the number correctly or not. Bar-Code: Calculation Add together the value of all of the digits in odd positions (digits 1, 3, 5, 7, 9 and 11). 6 + 9 + 8 + 0 + 0 + 9 = 32 Multiply that number by 3. 32 * 3 = 96 Add together the value of all of the digits in even positions (digits 2, 4, 6, 8 and 10). 3 + 3 + 2 + 0 + 3 = 11 Add this sum to the value in step 2. 96 + 11 = 107 Take the number in Step 4. To create the check digit, determine the number that, when added to the number in step 4, is a multiple of 10. 107 + 3 = 110 The check digit is therefore 3. 20