1. Digital Information Technology
Introduction

2. 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

3. 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

4. Computer System Components

5. 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 ( )
2nd generation – Transistors ( )
3rd generation – Integrated circuits ( )
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?

6. 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

7. 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

8. 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

9. 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

10. 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?

11. 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

12. 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

13. 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)
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?

14. 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

15. 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

16. 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

17. 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