NT1210Introduction to Networking

• Name: Williams Obinkyereh

MSc. IT, Post Masters Software Engineering

DSC (Doctor of Computer Science) Student.

• Contacts:

• Phone: 612-516-9712

• Email: obinkytt@yahoo.co.uk

Introduction• Class introduction

• Introduction of Course Syllabus.– Course Summary– Lab Infrastructure (Mock)– Course Plan– Evaluation– Academic integrity

• Discussion and questions about syllabus.

• Send me email: Name, phone number and a reliable email address.

NT1210 Introduction to Networking

Unit 1:

Chapter 1, Introduction to Computer Data

4

Objectives

Identify the major needs and stakeholders for computer networks and network applications.

Describe how digital devices store data.

Describe the differences between input and output devices.

5

Various Types of Computer/Computing Devices

Figure 1-1Images of Various Types of Computers/Computing Devices6

Introducing Data and Information, Bits and Bytes

Computers use binary digits (bits) to record information electronically

Bits represent either value of 0 or 1

Bit is smallest unit of data computers work with

Computers work with multi-digit binary numbers Nibble

Byte

Word

Doubleword

7

Nibble, Byte, Word, Double Word

Figure 1-2Nibble, Byte, Word, Double Word8

Kilobyte, Megabyte, Gigabyte, Terabyte

Table 1-1Kilobyte, Megabyte, Gigabyte, Terabyte9

Top Level Computer Components

PC

IR

MAR

MBR

I/O AR

I/O BR

Execution Unit or ALU

Execution Unit or ALU

CPU

Buffers

Instruction

Instruction

Data

Data

Main Memory

I/O Modules

System bus

VON NEUMANN ARCHITECTURE• von Neumann architecture: Programs and data are

stored in memory (stored-memory concept).• Consists of processor, memory and devices.• Data are carried along buses between components.

11

Processor Memory Devices

Cache

Bus

Control

Datapath

Registers

Input

Output

Random Access Memory (RAM)

Physically exists as set of microchips installed on plastic card (memory module)

Central Processing Unit (CPU) uses RAM like people use notepad Stores binary value so can use it later Can read data from RAM to recall value stored earlier

CPU sends electrical signal over bus (electrical pathway) to communicate with RAM

12

Converting Binary 01111011 to Decimal 123

Figure 1-7

1. Multiply the decimal digit value times the binary value in each of the eight columns.

2. Add the eight numbers found from the previous step (bottom row in the table).

Converting Binary 01111011 to Decimal 12313

Unsigned Integers in Computers, Various Sizes

Table 1-2

Size of Storage

Number of Bits

Range, From 0 to 2N – 1

Byte 8 0 - 255 28 - 1

Word 16 0 – 65,535 216 - 1

Doubleword 32 0 – 4,294,967,296 232 - 1

NOTE: Appendix B, Numeric Reference Tables, includes a table of decimal numbers 0-255, along with their 8-bit binary equivalent values.

14

Permanent Storage for Bits, Bytes

File Systems – Allow computer to store bytes of single file in many locations, while still keeping track of them

Files – Named set of related bytes of data that OS stores as single entity (based on name) to easily refer to data Unique name for each file Keep bytes in order Can be stored on any kind of physical storage device Can be copied or moved to other devices and stored there as well

File types examples Song (.mp3, .wav) YouTube video (.swf, .mpeg, .avi) Text file (.txt, .rtf) This PowerPoint presentation (.ppt., .pptx) High-resolution image from space telescope (.png, .jpg)

15

The Process of Storing Files

1. Application knows addresses in RAM that hold contents of document

2. When user clicks save and names the file, OS sends file contents over bus to storage location (drive)

3. Drive stores file

Figure 1-9Creating a File on Disk 16

File Systems and Directories

Directory - Part of file system used to organize files into hierarchy, keeping similar files together.

Figure 1-10Directory Structure: Disk Drive (C:) and DVD Drive (D:)17

Hard Disk Drives

Most common long-term computer storage devices today Store a lot of data Do not cost a lot of money Make data available all the time Storage topics

Hard Disks vs. Floppy Disks Hard Disk Drive Internals Writing Data to Sectors, Tracks Using Bus to Communicate

18

Hard Disks vs. Floppy Disks

Anatomy of 3.5" Floppy

The magnetic disk rotates between two liners inside the plastic jacket.

Figure 1-14a

http://encyclopedia2.thefreedictionary.com/floppy+disk

Internal Image, Floppy Disc 19

Hard Disks vs. Floppy Disks (cont.)

Figure 1-14bInternal Photo, Disk Drive

http://www.wdc.com/global/images/overview/en/OV_intdesktop.jpg

20

Writing Data to Sectors, Tracks

A platter has many locations that can hold magnetic charges. Physically, these locations exist in concentric circles, with each circle called a track. A sector refers to a subset of a track, as shown in the figure.

Figure 1-15Tracks and Sectors in a Single Disk Drive Platter21

Using a Bus to Communicate

Bus – Electrical pathway between internal components of computer

CPU uses bus to connect to hard drive (uses different electrical circuits to pass control information versus data)

Bus creates one or more electrical circuits between motherboard and disk drive To send bit value of 0, device varies electrical current in some pre-

determined way To send bit value of 1, device varies electrical current in some

other way

22

Break

23

Take 15

Other Permanent Storage Devices

Many competing types of permanent storage devices Different devices use different mechanisms to read and

write data USB Flash Drives CD and DVD Drives

24

Memory Hierarchy

25

Memory Hierarchy 2Memory issues Faster access time grater cost per bit Greater Capacity Smaller cost per bit Greater capacity slower access speed

Going down Memory Hierarchy1.Decreasing cost per bit2.Increasing capacity3.Increasing access time4.Decreasing frequency of access to the memory by the processor

Key Comparison Points, Permanent Storage

Short Description

Longer DescriptionHard Disk Drive (HDD)

Internal or External?

Does the device sit inside the computer, where is stays, or does it connect externally, so it can be easily moved between computers?

Both

Removable Media?

Can you remove the media from the drive, and insert new blank media to record more data?

No

Solid State?Solid state means that the device has no moving parts; moving parts make it more likely to break over time

No

Table 1-3Key Comparison Points, Permanent Storage27

Key Comparison Points, Permanent Storage (cont.)

Short Description

Longer DescriptionHard Disk Drive (HDD)

Read/Write Speed vs. Internal HDD

How fast do reads and writes occur, compared to an internal Hard Disk Drive (HDD)?

N/A

Price/GB Compared to HDD

How much does a typical device cost, per GigaByte (GB) of storage, relative to a hard disk drive (HDD)?

N/A

Table 1-3Key Comparison Points, Permanent Storage28

Key Comparison Points, USB Flash and Hard Disk Drives

Table 1-4

Short Description Hard DiskUSB Flash Drive

Internal or External? Both ExternalRemovable Media? No Yes*

Solid State? No YesRead/Write Speed vs. Internal HDD N/A Slower

Price/GB, at Publication, vs. HDD N/AMore Expensive

* Media cannot be removed from the drive, but the entire drive can be removed from the computer.

Note: Table information may change over time, but as of publication, USB flash drives work well for convenience, portability, and low price; but are too slow and too small to be used to replace a hard disk drive.

Key Comparison Points, USB Flash and Hard Disk Drives29

CD and DVD Drives

Compact Disc (CD) and Digital Video Disc (DVD) drives provide an entirely different class of computer storage as compared with hard disk drives and USB flash drives.

http://www.samsung.com/us/images/article/heromodule_DVDWriter.jpg

Figure 1-19Photo of USB DVD Drive 30

Input and Output (I/O)

Input : Creating information in computer Typing at keyboard Clicking with mouse Talking into computer microphone Recordings from video security camera connected to computer Statistics gathered by website Sales data from grocery store scans

Output: Presents information to users and for other purposes Computer display showing image or some video Computer speakers playing sound Printers printing images

31

How Keyboards Send Bits to Represent Letters

To physically send bits to the computer, the keyboard varies the electrical signal over time. Fro example, to send a binary 1, the keyboard might use a positive voltage (the current flows in one direction), and to send a 0, use a negative voltage (the current flows in the opposite direction).

Figure 1-20Wired Keyboard Connection to a PC System Unit32

How Keyboards Send Bits to Represent Letters (cont.)

Imagine the user has opened a text editor and is ready to practice typing “The quick brown fox jumped over the lazy river.” The graphic here illustrates what happens when the “T” is pressed (requires 2 keys, the Shift and “t” keys).

Figure 1-21Keyboard, Character Map, Bit Transmission, and Storing the Typed Character33

How Keyboards Send Bits to Represent Letters (cont.)1. User presses Shift and t character simultaneously for

uppercase “T”2. Keyboard processor looks at keyboard map to find binary

code associated with uppercase “T”3. Keyboard sends binary code such as 01010100 (actual

code might be different)4. CPU processes input using same keyboard map as

keyboard5. CPU stores newly-arrived input character “T” into RAM,

ready to serve it to active application6. Application takes over knowing letter “T” had been typed

and using some stipulated logic

34

How Keyboards Know What Key(s) You PressedQuestion: How does keyboard processor know what key is pressed? (HINT: Think in terms of simple light switch)

Consider what happens with simple electrical circuit when light turned on or off

Turn light switch on, completes electrical circuit that allows electrical current to flow and causes bulb to light

Flip light switch off, switch breaks circuit which stops flow of electrons which makes bulb go dark

Think of each keyboard key as separate on/off switches Press key, close circuit: Tells keyboard processor what key is

pressed Press multiple keys: Processor notices that multiple circuits have

current flowing (e.g., to create an uppercase letter)35

How Keyboards Send Bits to Represent Letters

Assuming uppercase T is pressed, here is how the current flows from each pressed key to the keyboard’s processor:

Figure 1-22Current Flow from Each Pressed Key to the Keyboard’s Processor

Keyboard basically monitors for pressed keys and then reacts (notices which electrical circuits have a current). The processor determines which circuits have current, then the keyboard processor uses the keyboard map to decode the circuits, and then it sends the binary code for the character to the CPU.

36

The Mouse

Allows control of computer’s actions but in much different way than keyboard: Point-and-click

When user moves mouse pointer, OS has list of actions to take depending on mouse action Single click of left mouse button causes OS application window

to become active Double click of left mouse button when pointing at icon or file

causes OS to start application or open file Single click of right mouse button causes app or OS to display

contextual menu based on where pointer was when click occurred

37

Other Mice

Wireless mice require no cable connected to mouse, which makes them more convenient Instead of sending bits over cable, mouse uses low-power radio

waves (typically Bluetooth)

Optical mouse uses light and light sensors to sense movement of mouse Mouse shines light, watches reflections, and senses movement

38

The Computer Display

Provides output Also called computer monitor or screen Shines light so user can see information on screen Sits outside system unit, connecting to system using cable When system powered off, display either shows nothing or

some kind of error message

39

Printers

Convert computer file to image on paper Uses method similar in concept to how display uses pixel

map to create image on screen Uses number of dots on paper organized into grid Printers identified by how many dots per inch (DPI) they

print in a square inch More dots per inch=Better print quality

Computer has to “translate” from its file to mapping of dots to print Example: Word processor has bytes that represent “The quick

brown fox jumps over the lazy river.” as ASCII stored in RAM To print, printer driver translates bytes to correct format to

determine which dots to print on paper to form each letter

40

Summary: This Chapter… Defined concepts behind bits and bytes Described in general terms how computers store data in

Random Access Memory (RAM) Explained how computers represent text characters using

bits held in RAM Discussed how computer file systems organize data Described in general terms how computers store data on

drives Explained general steps that occur when a key is pressed

on keyboard Described the basic information that a mouse sends to a

computer to move the mouse pointer Explained the concepts behind a computer display’s pixel

map, and how computers use bits to represent pixel color41

Questions? Comments?

42