DIGITAL INFORMATION
TECHNOLOGY
Introduction
Learning Objectives
• Identify the major hardware components of a computer
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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
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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