1. Categories of Computers
Understanding Computers
Lecture # 2
Categories of Computers
Waseem Gulsher

2. Computers To Fit Every Need
Six basic categories of computers:
Embedded computers
Mobile devices
Personal computers
Servers
Mainframe computers
Supercomputers

3. Embedded Computers Embedded Computers
Embedded into a product and designed to perform specific
tasks or functions for that product
Cannot be used as general-purpose computers
Often embedded into:
Household appliances
Thermostats
Sewing machines
Treadmills
Answering machines
Cars

4. Mobile Devices Mobile Device
A very small device with some type of built-in computing or Internet capability
Typically has a small screen and keyboard
Examples:
Smartphones
Handheld gaming devices
Portable digital media players
Media tablets

5. Personal Computers (PCs)
Personal Computer (PC)
Small computer designed to be used by one person at a
time
Also called a microcomputer
Available in different sizes and shapes
Desktop Computers
On or next to a desk
Tower case, desktop case, or all-in-one
PC or Macintosh
Not portable

6. Portable Computers Portable Computers
Designed to be carried around easily
Fully functional computers
Notebook (laptop) computers
Typically use a clamshell design
Tablet computers
Usually use a digital pen/stylus or touch screen
No physical keyboard; can use on-screen or attached keyboard
Hybrid notebook-tablet computers
Netbooks
Smaller and have more limited features than conventional notebooks

7. Portable Computers 40

8. Servers Server A medium-sized computer used to host programs
and data for a small network
Sometimes referred to as a minicomputer
Users connect via a network with a
computer, thin client, or dumb terminal
Virtualization
Creating virtual rather than actual environments (often used to share a server
for increased efficiency)

9. Mainframe Computers Mainframe Computer
Powerful computer used by many large organizations to
manage large amounts of centralized data
Standard choice for hospitals, universities, large businesses, banks, government offices
Located in climate-controlled data centers and connected
to the rest of the company computers via a network
Larger, more expensive, and more powerful than servers
Usually operate 24 hours a day
Also called high-end servers or enterprise-class servers

10. Mainframe Computers

11. Supercomputers Supercomputer
Fastest, most expensive, most powerful type of computer
Generally run one program at a time, as fast as possible
Can cost several million dollars each
Tend to be very large and contain a large number of CPUs
Titan is one of the fastest computers in the world

12. Supercomputers

13. Computer Networks and the Internet

14. Computer Networks and the Internet
A collection of hardware and other devices that are
connected together
Users can share hardware, software, and data
Users can communicate with each other
Network Servers
Manage resources on a network

15. Computer Networks and the Internet
Computer networks exist in many sizes and types
Home networks
School and small office networks
Large corporate
Public wireless networks
Mobile telephone networks 50

16. Computer Networks and the Internet

17. What Are the Internet and the World Wide Web?
The largest/most well-known computer network in the
world
Individuals connect using an Internet service provider (ISP)
World Wide Web
One resource (a vast collection of Web pages) available
through the Internet
Web sites contain Web pages stored on Web servers
Viewed using a Web browser (Internet Explorer, Chrome,
Safari, Firefox, Opera, etc.)
Offers a wide variety of information

18. What Are the Internet and the World Wide Web?

19. Accessing a Network or the Internet
Need a modem or network adapter to connect
Some networks require a username and password
Internet connections can be:
Direct (always-on) connections
Dial-up connections
Internet addresses are used to access resources on the
Internet
IP (Internet Protocol) address
Numeric address that identifies computers
( )

20. IP Addresses and Domain Names
Are numeric and unique
Domain Names
Correspond to IP addresses
Top-level domains (TLDs)
Identifies type of organization
or its location

21. Uniform Resource Locators (URLs)
Uniquely identifies a Web page, including
Protocol or standard being used
Web server hosting the page
Names of folders in which the Web page file is stored
Web page’s filename

22. Uniform Resource Locators (URLs)
Protocols:
Hypertext Transfer Protocol ( is typically used to
display Web pages ( is used for secure Web pages)
File Transfer Protocol (ftp://) is often used for file exchange

23. E-mail Addresses E-mail addresses consist of: Username
An identifying name
symbol
Domain name for the computer that will be handling the
person’s (mail server)
Pronouncing Internet addresses

24. Surfing the Web Web browser Used to display Web pages
Browser starting page or home page
The first page displayed when the browser is opened
To navigate to a Web page, you can:
Type a URL in the Address bar
Click a hyperlink – graphics or text linked to other Web pages
Select a Favorite/Bookmark or page from the History list 60

25. Searching the Web Search site: Helps you locate what you are
looking for
Typically search using keywords
Reference sites
Look up addresses,
telephone numbers, ZIP codes, maps, etc.

26. Number Systems

27. Common Number Systems System Base Symbols Used by humans?
Used in computers?
Decimal 10
0, 1, … 9
Yes No
Binary 2
0, 1
Octal 8
0, 1, … 7
Hexa- decimal 16
0, 1, … 9,
A, B, … F

28. Quantities/Counting (1 of 3)
Decimal
Binary
Octal
Hexa- decimal 1 2 10 3 11 4
100 5
101 6
110 7
111

29. Quantities/Counting (2 of 3)
Decimal
Binary
Octal
Hexa- decimal 8
1000 10 9
1001 11
1010 12 A
1011 13 B
1100 14 C
1101 15 D
1110 16 E
1111 17 F

30. Quantities/Counting (3 of 3)
Decimal
Binary
Octal
Hexa- decimal 16
10000 20 10 17
10001 21 11 18
10010 22 12 19
10011 23 13
10100 24 14
10101 25 15
10110 26
10111 27
Etc.

31. Conversion Among Bases
The possibilities:
Decimal
Octal
Binary
Hexadecimal

32. Quick Example
2510 = = 318 = 1916
Base

33. Decimal to Decimal (just for fun)
Octal
Binary
Hexadecimal

34. Weight
12510 => 5 x 100 = x 101 = x 102 =
Base

35. Binary to Decimal
Decimal
Octal
Binary
Hexadecimal

36. Technique Multiply each bit by 2n, where n is the “weight” of the bit
Binary to Decimal
Technique
Multiply each bit by 2n, where n is the “weight” of the bit
The weight is the position of the bit, starting from 0 on the right
Add the results

37. Example
Bit “0”
=> 1 x 20 = x 21 = x 22 = x 23 = x 24 = x 25 = 32
4310

38. Octal to Decimal
Decimal
Octal
Binary
Hexadecimal

39. Technique Multiply each bit by 8n, where n is the “weight” of the bit
Octal to Decimal
Technique
Multiply each bit by 8n, where n is the “weight” of the bit
The weight is the position of the bit, starting from 0 on the right
Add the results

40. Example
7248 => 4 x 80 = x 81 = x 82 =

41. Hexadecimal to Decimal
Octal
Binary
Hexadecimal

42. Hexadecimal to Decimal
Technique
Multiply each bit by 16n, where n is the “weight” of the bit
The weight is the position of the bit, starting from 0 on the right
Add the results

43. Example
ABC16 = C x 160 = 12 x 1 = B x 161 = 11 x 16 = A x 162 = 10 x 256 = 2560
274810

44. Decimal to Binary
Decimal
Octal
Binary
Hexadecimal

45. Technique Divide by two, keep track of the remainder
Decimal to Binary
Technique
Divide by two, keep track of the remainder
First remainder is bit 0 (LSB, least-significant bit)
Second remainder is bit 1
Etc.

46. Example
12510 = ?2
12510 =

47. Decimal to Octal
Decimal
Octal
Binary
Hexadecimal

48. Decimal to Octal
Technique
Divide by 8
Keep track of the remainder

49. Example
= ?8 8
19 2 8
2 3
= 23228

50. Decimal to Hexadecimal
Octal
Binary
Hexadecimal

51. Decimal to Hexadecimal
Technique
Divide by 16
Keep track of the remainder

52. Example
= ?16
77 2 16
= D
0 4
= 4D216

53. The Systems Unit: Processing and Memory

54. Inside the System Unit System Unit The main case of a computer
Houses the processing hardware for a computer
Also contains storage devices, the power supply, and cooling fans
Houses processor, memory, interfaces to connect to
peripheral devices (printers, etc), and other components
With a desktop computer, usually looks like a rectangular
box

55. Inside the System Unit

56. Inside the System Unit The Motherboard Computer Chip
Very small pieces of silicon or other semi-conducting
material onto which integrated circuits are embedded
Circuit Board
A thin board containing computer chips and other
electronic components
System Board
The main circuit board inside the system unit to which
all devices must connect

57. Inside the System Unit
External devices (monitors, keyboards, mice, printers)
Wireless devices (e.g., Bluetooth)
Power Supply
Connects to the motherboard to deliver electricity (personal computer)
Portable computers use rechargeable battery pack
Nonremovable batteries more difficult and expensive to replace

58. Inside the System Unit Drive Bays
Rectangular metal racks inside the system unit that house storage devices
Hard drive, CD/DVD drive, flash memory card reader
Connected to the motherboard with a cable
Processors
The CPU (Central Processing Unit)
Circuitry and components packaged together and connected directly to the motherboard
Does the vast majority of processing for a computer
Also called a processor; called a microprocessor when talking about personal computers 20

59. Inside the System Unit Dual-core CPU
Contains the processing components (cores) of two
separate processors on a single CPU
Quad-core CPU
Contains four cores
Multi-core processors allow computers to work on more than one task at a time
Typically different CPUs for desktop computers, portable computers, servers, mobile devices, consumer devices, etc.
Personal computer CPU often made by Intel or AMD
Media tablets and mobile phones use processors made by other companies such as ARM

60. Inside the System Unit

61. Inside the System Unit Processing Speed
CPU clock speed is one measurement of processing speed
Rated in megahertz (MHz) or gigahertz (GHz)
Higher CPU clock speed = more instructions processed per second
Alternate measure of processing speed is the number of
instructions a CPU can process per second
Megaflops (millions), gigaflops (billions), teraflops
(trillions)
Benchmark tests can be used to evaluate overall processing speed

62. Inside the System Unit Word Size
The amount of data that a CPU can manipulate at one time
Typically 32 or 64 bits
Cache Memory
Special group of very fast memory chips located on or
close to the CPU
Level 1 is fastest, then Level 2, then Level 3
More cache memory typically means faster processing
Usually internal cache (built into the CPU)

63. Inside the System Unit Bus Width, Bus Speed, and Bandwidth
A bus is an electronic path over which data can
travel
Found inside the CPU and on the motherboard
Bus width is the number of wires in the bus over
which data can travel
A wider bus allows more data to be transferred at one time