Transforming Datainto Information

lesson 3essential concepts

This lesson includes the following sections:

• How Computers Represent Data

• How Computers Process Data

• Factors Affecting Processing Speed

• Extending the Processor's Power to Other Devices

• CPUs Used in Personal Computers

• Magnetic Storage Devices

• Optical Storage Devices

• Binary Numbers

• Bits and Bytes

• Text Codes

How Computers Represent Data

How Computers Represent Data –Binary Numbers

• Computer processing is performed by transistors, switches that can be on and off.

• All computer data is converted to a series of binary numbers – 1 and 0. You see a word as letters; the computer sees it as a series of 1s and 0s.

• If a transistor is assigned a value of 1, it is on. If its value is 0, it is off.

Ten differentsymbols inthe decimalsystem

Numbers above 9 use more than 1 digit

• A single unit of data--called a bit--is the value assigned to one transistor (1 or 0). A bit is the smallest unit of data a computer can use.

• Eight bits make up one byte. A byte can store one alphanumeric character.

• With one byte, the computer can represent one of 256 different symbols or characters.

.

How Computers Represent Data - Bits and Bytes

1 0 1 1 0 0 1 01 0 0 1 0 0 1 01 0 0 1 0 0 1 11 1 1 1 1 1 1 1

EBCDIC -- an early text code, used mainly in older mainframe systems.

ASCII -- assigns each character 1 byte of data, used in nearly all PCs.

Unicode -- assigns each character 2 bytes of data, capable of including all the characters of all the languages in the world.

How Computers Represent Data - Text Codes

A text code is a system that uses binary numbers to represent characters understood by humans. The primary text code systems are:

How Computers Process Data

• Where Processing Occurs

• The CPU

• Memory

• Processing takes place in the central processing unit (CPU).

• The computer’s memory plays a crucial role in processing data.

• The CPU and memory are attached to the motherboard, which connects all the computer’s devices together.

How Computers Process Data -Where Processing Occurs

• The CPU includes a control unit and an arithmetic logic unit (ALU).

• The control unit directs the flow of data through the CPU, and to and from other devices. The control unit stores microcode, instructions for all the tasks the CPU can perform.

• The actual manipulation of data takes place in the ALU. The ALU can perform arithmetic and logic operations.

• The ALU is connected to small memory areas -- called registers -- that hold data and instructions while they are processed.

How Computers Process Data – The CPU

• Random-access memory (RAM) is volatile (temporary). Programs and data can be written to and erased from RAM as needed.

• Read-only memory (ROM) is nonvolatile (permanent). It holds instructions that run the computer when it is first turned on.

• The CPU accesses each location in memory by using a unique number, called a memory address.

How Computers Process Data –Memory

• The size of the CPU’s registers (word size) determines how much data the computer can process at one time.

• The more RAM a PC has, the more program instructions and data can be held in memory.

• The system clock sets the pace for the CPU. Speed is measured in Hertz (Hz), or cycles per second.

• A bus is a path between the components of a computer, on which data and instructions travel. The wider the bus, the more data it can carry.

• Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.

Factors Affecting Processing Speed

More RAM = Better Performance!

• External devices are connected to the system by ports on the back of the computer. PCs feature ports for devices such as a printers and mice.

• A serial port transmits one bit at a time; a parallel port transmits one byte at a time.

• If the PC does not have a port for an external device, you can install an expansion board into one of the PC’s empty expansion slots.

Extending the Processor's Power to Other Devices

Common Ports

CPUs Used in Personal Computers

• CPU Manufactures

• RISC and Parallel Processing

CPUs Used in Personal Computers – CPU Manufacturers

• Intel Corp. is the world’s largest maker of microprocessors. Intel’s 80x86 processor family includes the 80286, 80386, 80486, and Pentium models.

• Advanced Micro Devices (AMD) has challenged Intel in the IBM-compatible market. AMD processors include the K6 and Athlon lines.

• Cyrix is best known as a maker of low-cost chips for budget PCs.

• Motorola makes processors for Macintosh and PowerPC computers. Motorola processors include the 680x0, PowerPC, G3, and G4.

CPUs Used in Personal Computers - RISC Processors

• Nearly all PC processors are called complex instruction set computing (CISC) processors because they contain large instruction sets.

• Reduced instruction set computing (RISC) chips run faster than CISC chips because they use a smaller instruction set. RISC chips are used in mainframe systems, minicomputers, and workstations.

• Multiple processors can be used in a single system, sharing processing tasks. This type of system is called a parallel processing system.

Magnetic Storage Devices

• How Magnetic Storage Works

• Formatting

• Disk Areas

• Diskettes

• Hard Disks

Magnetic Storage Devices - How Magnetic Storage Works

• A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions.

• Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.

• A disk drive uses read/write heads containing electromagnets to create magnetic charges on the disk.

Random particles(no data stored)

Current flow(write operation)

Organized particles(represent data)

Medium

Write head

Magnetic Storage Devices - Formatting

• Before a magnetic disk can be used, it must be formatted—a process that maps the disk's surface and determines how data will be stored.

• During formatting, the drive creates circular tracks around the disk's surface, then divides each track into sectors.

• The OS organizes sectors into groups, called clusters, then tracks each file's location according to the clusters it occupies.

Formatted Disk

Magnetic Storage Devices -Disk AreasWhen a disk is formatted, the OS creates fourareas on its surface:

• Master boot record – an area of the disk containing a small program that runs when you first start (boot) the computer

• File allocation table (FAT) – a log that records each file's location and each sector's status

• Root folder – enables the user to store data on the disk in a logical way

• Data area – the portion of the disk that actually holds data

Magnetic Storage Devices - Diskettes

• Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies).

• Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium.

• Diskettes come in two sizes: 5.25-inch and 3.5-inch.

3.5 inchfloppy

and drive

Magnetic Storage Devices - Hard Disks

• Hard disks use multiple platters, stacked on a spindle. Each platter has two read/write heads, one for each side.

• Hard disks use higher-quality media and a faster rotational speed than diskettes. As a result, a hard disk can store many times more data than a floppy disk.

Read/write heads

Optical Storage Devices

• How Optical Storage Works

• CD-ROM

• DVD-ROM

• Other Optical Storage Devices

Optical Storage Devices – How Optical Storage Works

• An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data.

• To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.

• When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).

1 0

Optical Storage Devices – CD-ROM

• In PCs, the most commonly used optical storage technology is called Compact Disk Read-Only Memory (CD-ROM).

• A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio.

Optical Storage Devices - DVD-ROM

• A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.

• Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.

• DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.

Optical Storage Devices - Other Optical Storage Devices

• A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk.

• A CD-Rewritable (CD-RW) drive lets you record a CD, then write new data over the already recorded data.

• PhotoCD technology is used to store digital photographs.

• Explain why computers use the binary number system.

• List the two main parts of the CPU and explain their function.

• List three hardware factors that affect processing speed.

• List four common types of storage devices.

• Explain how data is stored on the surface of magnetic and optical disks.

lesson 3 review Essential concepts