Input and Processing Chapter 2 - Computers- Understanding Technology

Information Processing Cycle Input Processing Output Storage

Input Devices Keyboard – alphanumeric and special function Touchscreen – ATMs, restaurants, airport checkin counters, kiosks, smart boards in classrooms Mouse –Mouse has used a rubber-coated ball on the bottom of the mouse; movement of the mouse on a surface results in rotation of the ball which is recorded by sensors in the mouse –An optical mouse uses a light sensor instead of a ball to track movement

Input Devices (cont.) Trackball – plastic sphere resting on rollers, often used in laptop computers Touchpads – you move the pointer by sliding your finger across the surface of the pad Joystick, pointer in notebook computers Pens, tablets – PDA’s, graphics tablet

Input Devices (cont.) Optical scanners Bar code reader Digital camera Webcams and digital video cameras Microphone

Input Devices Operating systems such as Windows and Macintosh employ a graphical user interface (GUI – pronounced gooey) in which the user issues command by using a mouse to make selections With DOS (previous operating system for IBM-compatible computers), users issued commands through typing on a keyboard

Computer Representation of Data Bit (either 0 or 1) Byte - 8 bits (0-255) ASCII (7 bit encoding, primarily in small computers) EBCDIC (8 bit encoding, primarily in large computers) Unicode (16 bit) – non-English characters are represented (~65,000)

System Unit in Desktop Computer Power supply – converts AC to DC Storage bay or bays – site where storage device such as floppy drive, hard drive, or CD/DVD drive is installed –Internal bays – concealed entirely within system unit –Exposed bay – used where access is needed to device, such as insertion and removal of floppy disk or CD/DVD

System Unit (cont.) Motherboard – thin sheet which has a number of components connected to it –CPU –System clock and battery –Slots for RAM chips –One or more read-only memory chips –Expansion slots –Ports for connecting input and output devices –Buses, which allow communication between components in the computer

Central Processing Unit Machine or instruction cycle – fetch, decode, execute, store Arithmetic/logic unit (ALU) Registers – temporary storage locations that can be accessed much faster than locations outside of the CPU; instruction registers, data registers, storage registers System clock – generates pulses which synchronize activity within computer

CPU (cont.) Clock speed is measured in hertz (pulses per second) – megahertz (1 million/sec) Coprocessors – math, graphical

Memory Random access memory (RAM) – each memory location has its own address so CPU can go directly to instructions and data it needs Random access memory is reusable (new data or instructions can replace what was formerly there) Random access memory is volatile – it only contains information while power is on

Cache Memory Cache memory contains data and instructions recently used by processor; when CPU looks for data or instructions, it first looks in the cache Because there is often repeat use of data or instructions, this decreases time required to get the information

Read-only Memory (ROM) ROM contains instructions or data permanently there; does not depend on maintaining continuous power ROM contains BIOS (basic input/output system) program which is the program that boots or starts the computer when it is turned on

Flash Memory Nonvolatile memory that can be reused Flash memory used in many handheld devices, including digital cameras, PDAs, cell phones, and MP3 players Some flash memory is portable and portable flash drives are becoming very common

Expansion and Ports Expansion boards – sound, video, graphics, modem, etc.; notebook computers often use PC or PCMCIA cards Ports – external plug-in slot –serial or communications (COM) (one bit at a time) –Parallel (LPT)– traditionally used to connect printer –Video – connect monitor –USB (Universal Serial Bus) – can be used to connect many type of devices and many devices can be connected together using a single USB port

Buses A bus is a pathway within a computer along which bits are transmitted Bus width refers to number of bits that can be transmitted at one time; e.g. 32-bit bus Expansion bus – interacts with RAM and low-speed devices Local bus – high speed peripherals and connects directly to CPU