DIGITAL INFORMATION TECHNOLOGYIntroduction

Learning Objectives• Identify the major hardware components of a computer

system• Describe the evolution of computer processor technology• Differentiate the various types of input and output

technologies and their uses• Identify the characteristics of computer memory and

memory capacity terminology • Describe the design and functioning of the central

processing unit• Discuss the concept of digital technology and how it

impacts storage and processing for character data, numbers, and various forms of multimedia

Introduction• E-commerce is enabled by a wide range of digital information

technologies including computer hardware, software, databases, networks, the Internet/Web, and various forms of multimedia

• In this discussion we focus on the components of a computer system, and how these components function, to gain an understanding of the capabilities and limitations of digital information technology

• A computer system consists of the following:• Central processing unit (CPU)• Primary storage• Secondary storage• Input technologies• Output technologies• Communication technologies

Computer System Components

Processor Technology Evolution• Computer processing hardware technology has evolved

quite dramatically in the past 60+ years• The generations of hardware technology include:

• 1st generation – Vacuum tubes (1946-1956)• 2nd generation – Transistors (1957-1963)• 3rd generation – Integrated circuits (1964-1979)• 4th generation – Ultra-large-scale integrated circuits (1980-present)• 5th generation – Massively parallel processing

• What are the trends associated with the evolution of hardware technology?

Processor Speed Terminology• As the speed of computer processors, data access

devices, and data transmission continues to increase, new terminology is required to compare current capabilities with older technologies

• Time in a computer environment is represented in fractions of a second

• The following are common measures of time:• Millisecond = 1/1000 second• Microsecond = 1/1,000,000 second• Nanosecond = 1/1,000,000,000 second• Picosecond = 1/1,000,000,000,000 second

Input and Output Devices• Input and output (I/O) devices enable human-computer

interaction (HCI)• Input devices enable human data and actions to be

converted into a computer-understandable format• Examples include a keyboard and a mouse

• Output devices translate computer representations of data into a human-understandable format (text, images, sound, etc.)• Examples include monitors and printers

• Input and output devices have traditionally been physical devices, but the trend is toward more virtual I/O devices

Computer Memory• Storing characters, numbers, images, and other

multimedia files for organizations and individuals requires a massive amount of computer memory

• Luckily, as computer hardware technology has evolved, so has the computer memory capacity required to support new applications

• Example secondary storage devices include internal computer hard drives, external hard drives, CD/DVD, flash memory devices, and cloud-based storage services

• As storage requirements have continued to increase, new terminology is required to describe digital storage capacity

Hierarchy of Memory Capacity• Kilobyte

• Approximately one thousand bytes• A kilobyte is actually 1024 bytes (why?)

• Megabyte• One million (106) bytes

• Gigabyte• One billion (109) bytes

• Terabyte• One trillion (1012) bytes

• Petabyte• One quadrillion (1015) bytes

• Exabyte• One quintillion (1018) bytes

The Central Processing Unit• The central processing unit (CPU) performs the actual

computation inside any computer• The CPU is a microprocessor made up of millions of

microscopic transistors embedded in a circuit on a silicon wafer (or chip)

• The CPU and all components of a computer system process and store data using digital technology

• What is the unique characteristic of “digital” technology?

Digital Technology• Today’s computers are based on integrated circuits

(chips), each of which includes millions of subminiature transistors

• Each transistor can be in either an “on” or “off” position• The “on-off” states of transistors are described using

binary number system where each binary digit, or bit, has a value of either 1 or 0

• This digital concept enables the storage and processing of characters, numbers, and various forms of multimedia

Character Representation and Processing

• A sufficient number of bits to represent specific characters – letters, numbers, and special symbols – is known as a byte, usually 8 bits

• Because a bit has only two states, 0 or 1, the bits comprising a byte can represent any of 28, or 256, unique characters

• The two most commonly used coding schemes are:• For microcomputers - the American National Standard Code for

Information Interchange (ASCII), pronounced “ask-ee”• For mainframe computers – the Extended Binary Coded Decimal

Interchange Code (EBCDIC), pronounced “ebsa-dick”• ASCII and EBCDIC are sufficient for English and Western

European languages but are not large enough for Asian and other languages that use different alphabets

Number Representation and Processing

• Numbers in a computer are stored and processed using binary (base 2) representations

• Why?• Humans store numbers and do mathematical

computations using a decimal representation (base 10)• Why?• The ALU in a CPU can perform basic computations such

as add, subtract, multiply, divide, compare, and determine whether a number is positive, negative, or zero

• How does a computer perform these numerical processes?

Image Representation and Processing

• Pictures are represented by a grid overlay of the picture• Each dot on a screen, or pixel, can display one color• More pixels per square inch improve the picture clarity,

but also take more storage space and require more time to download

Image Representation and Processing (cont.)

• Each pixel can be displayed in a wide range of colors by varying the intensity of red, green and blue displayed for each pixel

• Two common image formats are:• Graphics Interchange Format (GIF), 8 bits per pixel, 256 colors• Joint Photographic Experts Group (JPEG), 24 bits per pixel, 16.7

million colors

Video Representation and Processing

• How is video storage and processing different from image storage and processing?

• Video files are digitally stored as a series of interrelated still images

• The file sizes vary depending on format, frame size, and frame rate (frames per second, fps)

• A typical fps rate is about 15-30, fast enough to fool the human eye and make the series of still images appear as natural movement

Audio Representation and Processing

• Every sound (wave) can be described by two characteristics – amplitude (loudness) and frequency (pitch)

• Digital recording measures the sound’s characteristics at discrete moments in time

• The conversion method from analog to digital affects the sound quality and the file size, it has three components:• Sampling rate – number of measurements in a period of time (KHz)• Sampling resolution – precision in measuring the sound within

each sample (8-bit, 16-bit, etc.)• Channels – mono or stereo

• For example, a telephone is 8KHz, 8-bit, mono; and a CD is 44KHz, 16-bit, stereo