SAM Prelim

Pervasive computing

• Also known as ubiquitous computing

• Computers have become an integral part of our lives

Basic computer literacy

• Knowing about and understanding computers and their uses is an essential skill today for everyone

Microcomputers in the early 80s

• Inexpensive personal computers

• Computer use increased dramatically

Computer Users and Professionals

Computer professionals include:

• Programmers

• Systems analysts

• Computer operations personnel

• Security specialists

Categories of Computers

• Embedded computers

• Mobile devices

• Personal computers

• Midrange servers

• Mainframe computers

• Supercomputers

Bit

The smallest unit of data that a binary computer can recognize (a single 1 or 0)

Byte

8 bits

Byte

terminology used to express the size of documents and other files, programs, etc.

Prefixes

are often used to express larger quantities of bytes: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), etc.

Numbering System

A way of representing numbers

Decimal numbering system

• Uses 10 symbols (0-9)

Binary Numbering System

• Uses only two symbols (1 and 0) to represent all possible numbers

ASCII (American Standard Code for Information Interchange)

coding system traditionally used with personal computers.

EBCDIC (Extended Binary-Coded Decimal Interchange Code)

developed by IBM, primarily for mainframe use

Unicode

newer code (32 bits per character is common); universal coding standard designed to represent text-based data written in any ancient or modern language

• Replacing ASCII as the primary text-coding system

Graphics

(still images such as photos or drawings)

Bitmapped images

A variety of bit depths are possible (4, 8, 24 bits)

More bits

more colors

Audio Data

Must be in digital form in order to be stored on or processed by a computer

Video Data

Displayed using a collection of frames, each frame contains a still image

Machine Language

• Binary-based language for representing computer programs the computer can execute directly

System Unit

The main housing of a computer

The Central Processing Unit (CPU)

circuitry and components packaged together and connected directly to the motherboard

Dual-core CPU

Contains the processing components (cores) of two separate processors on a single CPU

Quad-core CPU

Contains 4 cores

Intel or AMD

Usual CPU brands

CPU clock speed

One measurement of processing speed

Clockspeed

Measured in megahertz (MHz) or gigahertz (GHz)

Bus

An electronic path over which data can travel

Bus Width

The number of wires in the bus over which data can travel

Bus width and speed

determine the throughput (or bandwidth) of the bus

Arithmetic/Logic Unit (ALU)

Performs integer arithmetic and logical operations

Floating Point Unit (FPU)

Performs decimal arithmetic

Control unit

Coordinates and controls activities

Pre-fetch unit

Tries to fetch data and instructions before they are needed from cache or RAM

Decode unit

Translates instructions so they are understood by the control unit, ALU, and FPU

Internal cache and registers

Store data and instructions needed by the CPU

Bus interface unit

Allows the core to communicate with other CPU components

System clock

Timing mechanism within the computer system that synchronizes the computer’s operations

Machine cycle

The series of operations involved in the execution of a single machine level instruction

Chip-based storage

Memory refers to what

RAM (random access memory)

Computer’s main memory

Registers

High-speed memory built into the CPU; used by the CPU

ROM (read-only memory)

Non-volatile chips located on the motherboard into which data or programs have been permanently stored

Flash memory

Type of nonvolatile memory that can be erased and reprogrammed

Heat

A continuing problem for CPU and computer manufacturers

Fans

Used on most personal computers

Heat sinks

Small components typically made out of aluminum with fins that help to dissipate heat

Water cooling systems

Cool the computer with liquid-filled tubes

Expansion slot

A location on the motherboard into which expansion cards are inserted

Expansion card

A circuit board used to add additional functionality or to attach a peripheral device

ExpressCard modules

Designed for notebook computer expansion

Bus

An electronic path within a computer over which data travels

Expansion bus

Connects the CPU to peripheral (typically input and output) devices

Memory bus

connects CPU directly to RAM

Frontside bus

connects CPU to I/O bridge

Port

A connector on the exterior of a computer’s system unit to which a device may be attached

Nanotechnology

The science of creating tiny computers and components less than 100 nanometers in size

Quantum computing

Applies the principles of quantum physics and quantum mechanics to computers

Device

DVD drive, flash memory card reader, etc.

Medium

DVD disc, flash memory card, etc.

Logical file representation

The user’s view of the way data is stored

Physical file representation

The actual physical way the data is stored on the storage media as viewed by the computer

Storage technologies

Magnetic (conventional hard drives)

Optical (optical discs)

Electrons (flash memory media)

File

Anything stored on a storage medium, such as a program, document, digital image, or song

Filename

Name given to a file by the user

Folder

Name place on a storage medium into which files can be stored

Hard drive

used to store most programs and data

• Can be internal and external

• Can be encrypted

Magnetic hard drives

• Use metal hard disks

• Read/write heads magnetize particles to represent the data’s 0s and 1s

Solid-state drives (SSDs)

• Use flash memory technology

• Use less power and have no moving parts

• Particularly appropriate for portable computers

Hard disks are divided into

• Tracks

• Sectors

• Clusters

• Cylinders

Disk access time

• Total time that it takes for a hard drive to read or write data

  • Consists of seek time, rotational delay, and data movement time

Disk cache

Dedicated part of RAM used to store additional data adjacent to data retrieved during a disk fetch to improve system performance

Hybrid hard drive

• Combination of flash memory and magnetic hard drive

• Uses flash memory for cache

• Allows encryption to be built into the drive

Partitioning

• Logically divides the physical capacity of a single drive into separate areas, called partitions

  • Partitions function as independent hard drives

  • Referred to as logical drives

  • Increase efficiency (smaller drives use smaller clusters)

Partitions used to

• Create a recovery partition

• Create a new logical drive for data

• Create a dual boot system

File system

Determines the cluster size, maximum drive size, and maximum file size

• FAT, FAT32, and NTFS

Hard drive interface standards

• Determine how a drive connects to the computer

Common standards

• Parallel ATA (PATA): older, slower standard

• Serial ATA (SATA)

• eSATA

• SCSI and the newer serial attached SCSI (SAS)

• Fibre Channel

• Fibre Channel over Ethernet (FCoE)

• Internet SCSI (iSCSI)

eSATA

uses USB or Firewire via expansion card for faster speeds

Optical discs

• store data optically (using laser beams)

  • Divided into sectors like magnetic discs but use a single spiral track 

  • Data is stored in 0s and 1s

Read-only

Surface is molded or stamped to represent the data

Recordable or rewritable

Reflectivity of the surface is changed by a laser

Optical drives

• Designed for the type of disc: CD, DVD, or Blu-Ray Disc (BD)

  • Can be read-only, recordable, or rewritable

  • Downward compatible

  • Can support single or dual-layer discs

Burning

Recording data onto a disc

CD discs

Use infrared lasers; hold 650 MB

DVD discs

Use red lasers; hold 4.7 GB (single-layer)

BD discs

Use blue-violet lasers; hold 25 GB (single-layer)

Read-only disc

Can be read from, but not written to, by the user

• CD-ROM (compact disc read-only memory)

• DVD-ROM (digital versatile disc read-only memory)

• BD-ROM (Blu-Ray disc read-only memory)

Normally come pre-recorded

• Software programs

• Clip art and other graphics

• Music

• Movies

• Games (UMD, Wii, Xbox, etc.)

Recordable disc

Can be written to, but cannot be erased and reused

• CD-R discs

• DVD-R/DVD+R discs; can be dual-layer

• BD-R; can be dual-layer

Rewritable disc

Can be recorded on, erased, and overwritten just like magnetic discs

• CD-RW

• DVD-RW

• BD-RE; can be dual-layer

Chip-based storage medium

• No moving parts so more resistant to shock and vibration, require less power, make no sound

• Solid-state storage system

Flash memory card

A small card containing one or more flash memory chips, controller chips, and metal contacts to connect the card to the device or reader that it is being used with

USB flash drives

Consist of flash memory media and a reader in a single self-contained unit

Remote storage

Using a storage device not directly a part of the computer being used

Network storage

Via a local network

Network Attached Storage (NAS)

Connected directly to a network

Storage area network (SAN)

Separate network of hard drives or other storage devices which is attached to the main network

Online storage or cloud storage

Accessed via the Internet