Monday, October 31

New Oromo musics 2016"2017"|Maal Sodaatta!|by Abdi fikadu

Saturday, August 27

Saturday, May 14

Thursday, April 14

Samsung Galaxy Secret Code

*#06# (Display IMEI number)
*#1234# (Display current firmware)
*#*#4636#*#* (Diagnostic and general settings mode)
*#*#7780#*#* (Factory soft reset)
or *#7780#
*2767*3855# (Factory hard reset to ROM firmware default settings)
*2767*4387264636# (To display product code)
*#272*imei#* (Display/change CSC code)
or *#272*HHMM#*
*#*#1472365#*#* (GPS test settings)
*#*#197328640#*#* (Service mode main menu)
*#12580*369# (SW & HW Info)
*#232337# (Bluetooth Address)
*#232331# (Bluetooth Test Mode)
*#232338# (WLAN MAC Address)
*#0228# (ADC Reading)
*#32489# (Ciphering Info)
*#2263# (RF Band Selection)
*#9090# (Diagnostic ConfiguratioN)
*#7284# (USB I2C Mode Control)
*#232339# (WLAN Test Mode)
*#0842# (Vibra Motor Test Mode)
*#0782# (Real Time Clock Test)
*#0673# (Audio Test Mode)
*#0*# (General Test Mode)
*#872564# (USB Logging Control)
*#4238378# (GCF Configuration)
*#0283# (Audio Loopback Control)
*#1575# (GPS Control Menu)
*#3214789650# (LBS Test Mode)
*#745# (RIL Dump Menu)
*#03# (NAND Flash S/N)
*#0589# (Light Sensor Test Mode)
*#0588# (Proximity Sensor Test Mode)
*#273283*255*3282*# (Data Create Menu)
*#34971539# (Camera Firmware Update)
*#526# (WLAN Engineering Mode)
*#746# (Debug Dump Menu)
*#9900# (System Dump Mode)
*#44336# (Sofware Version Info)
*#273283*255*663282*# (Data Create SD Card)
*#3282*727336*# (Data Usage Status)
*#7594# (Remap Shutdown to End Call TSK)
*#0289# (Melody Test Mode)
*#2663# (TSP / TSK firmware update)
*#528# (WLAN Engineering Mode)
*#7412365# (Camera Firmware Menu)
or *#*#34971539#*#*
*#80# (Unknown)
*#07# (Test History)
*#3214789# (GCF Mode Status)
*#272886# (Auto Answer Selection)
*#8736364# (OTA Update Menu)
*#301279# (HSDPA/HSUPA Control Menu)
*#7353# (Quick Test Menu)
*2767*4387264636# (Sellout SMS / PCODE view)
*#7465625# (View Phone Lock Status)
*7465625*782*# (Configure Network Lock NSP)
*7465625*27*# (Insert Network Lock Keycode NSP/CP)
#7465625*27*# (Insert Content Provider Keycode)
#7465625*782*# (Insert Partitial Network Lock Keycode)
*7465625*77*# (Insert Network Lock Keycode SP)
#7465625*77*# (Insert Operator Lock Keycode)
*7465625*638*# (Configure Network Lock MCC/MNC)
#7465625*638*# (Insert Network Lock Keycode)

Samsung Galaxy Secret Code

Thursday, April 7

Introduction to computer science Full course

Downlaod Full course

Friday, March 18

ntroduction
Computer Hardware is the physical part of a computer, as distinguished from the computer software that executes or runs on the hardware. The hardware of a computer is infrequently changed, while software and data are modified frequently. The term soft refers to readily created, modified, or erased. These are unlike the physical components within the computer which are hard.

When you think of the term computer hardware you probably think of the guts inside your personal computer at home or the one in your classroom. However, computer hardware does not specifically refer to personal computers. Instead, it is all types of computer systems. Computer hardware is in embedded systems in automobiles, microwave ovens, CD players, DVD players, and many more devices. In 2003, only 0.2% of all microprocessors sold were for personal computers. How many other things in your house or your classroom use computer hardware?

Inside Computer

Motherboard
The motherboard is the body or mainframe of the computer, through which all other components interface. It is the central circuit board making up a complex electronic system. A motherboard provides the electrical connections by which the other components of the system communicate. The mother board includes many components such as: central processing unit (CPU), random access memory (RAM), firmware, and internal and external buses.

Motherboard

Central Processing Unit
The Central Processing Unit (CPU; sometimes just called processor) is a machine that can execute computer programs. It is sometimes referred to as the brain of the computer.

CPU Diagram

There are four steps that nearly all CPUs use in their operation: fetch, decode, execute, and writeback. The first step, fetch, involves retrieving an instruction from program memory. In the decode step, the instruction is broken up into parts that have significance to other portions of the CPU. During the execute step various portions of the CPU, such as the arithmetic logic unit (ALU) and the floating point unit (FPU) are connected so they can perform the desired operation. The final step, writeback, simply writes back the results of the execute step to some form of memory.

Random Access Memory
Random access memory (RAM) is fast-access memory that is cleared when the computer is power-down. RAM attaches directly to the motherboard, and is used to store programs that are currently running. RAM is a set of integrated circuits that allow the stored data to be accessed in any order (why it is called random). There are many different types of RAM. Distinctions between these different types include: writable vs. read-only, static vs. dynamic, volatile vs. non-volatile, etc.

RAM

Firmware
Firmware is loaded from the Read only memory (ROM) run from the Basic Input-Output System (BIOS). It is a computer program that is embedded in a hardware device, for example a microcontroller. As it name suggests, firmware is somewhere between hardware and software. Like software, it is a computer program which is executed by a microprocessor or a microcontroller. But it is also tightly linked to a piece of hardware, and has little meaning outside of it. Most devices attached to modern systems are special-purpose computers in their own right, running their own software. Some of these devices store that software (“firmware”) in a ROM within the device itself

Power Supply
The power supply as its name might suggest is the device that supplies power to all the components in the computer. Its case holds a transformer, voltage control, and (usually) a cooling fan. The power supply converts about 100-120 volts of AC power to low-voltage DC power for the internal components to use. The most common computer power supplies are built to conform with the ATX form factor. This enables different power supplies to be interchangable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard, and provide support for modern functions such as standby mode.

Removable Media Devices
If your putting something in your computer and taking it out is most likely a form of removable media. There are many different removable media devices. The most popular are probably CD and DVD drives which almost every computer these days has at least one of. There are some new disc drives such as Blu-ray which can hold a much larger amount of information then normal CDs or DVDs. One type of removable media which is becoming less popular is floppy disk.

CD
CDs are the most common type of removable media. They are inexpensive but also have short life-span. There are a few different kinds of CDs. CD-ROM which stands for Compact Disc read-only memory are popularly used to distribute computer software although any type of data can be stored on them. CD-R is another variation which can only be written to once but can be read many times. CD-RW (rewritable) can be written to more than once as well as read more than once. Some other types of CDs which are not as popular include Super Audio CD (SACD), Video Compact Discs (VCD), Super Video Compact Discs (SVCD), PhotoCD, PictureCD, CD-i, and Enhanced CD.

CD-ROM Drive

There are two types of devices in a computer that use CDs: CD-ROM drive and a CD writer. The CD-ROM drive used for reading a CD. The CD writer drive can read and write a CD. CD writers are much more popular are new computers than a CD-ROM drive. Both kinds of CD drives are called optical disc drives because the use a laser light or electromagnetic waves to read or write data to or from a CD.

DVD
DVDs (digital versatile discs) are another popular optical disc storage media format. The main uses for DVDs are video and data storage. Most DVDs are of the same dimensions as compact discs. Just like CDs there are many different variations. DVD-ROM has data which can only be read and not written. DVD-R and DVD+R can be written once and then function as a DVD-ROM. DVD-RAM, DVD-RW, or DVD+RW hold data that can be erased and re-written multiple times. DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. The devices that use DVDs are very similar to the devices that use CDs. There is a DVD-ROM drive as well as a DVD writer that work the same way as a CD-ROM drive and CD writer. There is also a DVD-RAM drive that reads and writes to the DVD-RAM variation of DVD.

DVD

Blu-ray
Blu-ray is a newer optical disc storage media format. Its main uses are high-definition video and data storage. The disc has the same dimensions as a CD or DVD. The term “Blu-ray” comes from the blue laser used to read and write to the disc. The Blu-ray discs can store much more data then CDs or DVDs. A dual layer Blu-ray disc can store up to 50GB, almost six times thecapacity of a dual layer DVD (WOW!). Blu-ray discs have similar devices used to read them and write to them as CDs have. A BD-ROM drive can only read a Blu-ray disc and a BD writer can read and write a Blu-ray disc.

Floppy Disk
A floppy disk is a type of data storage that is composed of a disk of thin, flexible(“floppy”) magnetic storage medium encased in a square or rectangular plastic shell. Floppy disks are read and written by a floppy disk drive. Floppy disks are a dying and being replaced by the optical and flash drives. Many new computers do not come with floppy drives anymore but there are a lot of older ones with floppy drives lying around. While floppy disks are very cheap the amount of storage on them compared to the amount of storage for the price of flash drives makes floppy disks unreasonable to use.

Floppy Disk

Internal Storage
Internal storage is hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power. There are a few different types of internal storage. Hard disks are the most popular type of internal storage. Solid-state drives have grown in popularity slowly. A disk array controller is popular when you need more storage then a single har disk can hold.

Hard Disk Drive
A hard disk drive (HDD) is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Just about every new computer comes with a hard disk these days unless it comes with a new solid-state drive. Typical desktop hard disk drives store between 120 and 400GB, rotate at 7,200 rpm, and have a madia transfer rate of 1 Gbit/s or higher. Hard disk drives are accessed over one of a number of bus types, including parallel ATA(also called IDE), Serial ATA (SATA), SCSI, Serial Attached SCSI, and Fibre Channel.

Hard Drive

Solid-State Drive
A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. An SSD emulates a hard disk drive, thus easily replacing it in any application. SSDs have begun to appear in laptops because they can be smaller than HDDs. SSDs are currently more expensive per unit of capacity than HDDs which is why they have not caught on so quickly.

Disk Array Controller
A disk array controller is a device which manage the physical disk drives and presents them to the computer as logical units. It almost always implements hardware RAID. RAID (Redundant Array of Independent Drives) is a technology that employs the simultaneous use of two or more hard disk drives to achieve greater levels of performance, reliability, and/or larger data volume sizes. A disk array controller also provides additional disk cache.

Operate Database Application

Computer Hardware Peripherals

Introduction

A peripheral is a piece of computer hardware that is added to a computer in order to expand its abilities. The term peripheral is used to describe those devices that are optional in nature, as opposed to hardware that is either demanded or always required in principle. There are all different kinds of peripherals you can add your computer. The main disctinction among peripherals is the way they are connected to your computer. They can be connected internally or externally.

Buses

A bus is a subsystem that transfers data between computer components inside a computer or between computers. Unlike a point-to-point connection, a bus can logically connect several peripherals over the same set of wires. Each bus defines its set of connectors to physically plug devices, cards or cables together. There are two types of buses: internal and external. Internal buses are connections to various internal components. External buses are connections to various external components. There are different kinds of slots that internal and external devices can connect to.

Internal

Types of Slots

There are many different kinds of internal buses, but only a handful of popular ones. Different computers come with different kinds and number of slots. It is important to know what kind and number of slots you have on your computer before you go out and by a card that matches up to a slot you don’t have.

PCI

PCI (Peripheral Component Interconnect) is common in modern PCs. This kind of bus is being succeeded by PCI Express. Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as USB or serial, TV tuner cards and disk controllers. Video cards have outgrown the capabilities of PCI because of their higher bandwidth requirements.

PCI Slots

PCI Express

PCI Express was introduced by Intel in 2004. It was designed to replace the general-purpose PCI expansion bus and the AGP graphics card interface. PCI express is not a bus but instead a point-to-point conection of serial links called lanes. PCI Express cards have faster bandwidth then PCI cards which make them more ideal for high-end video cards.

PCMCIA

PCMCIA (also referred to as PC Card) is the type of bus used for laptop computers. The name PCMCIA comes from the group who developed the standard: Personal Computer Memory Card International Association. PCMCIA was originally designed for computer memory expansion, but the existence of a usable general standard for notbeook peripherals led to many kinds of devices being made available in this form. Typical devices include network cards, modems, and hard disks.

AGP

AGP (Accelerated Graphics Port) is a high-speed point-to-point channel for attaching a graphics card to a computer’s motherboard, primarily to assist in the acceleration of 3D computer graphics. AGP has been replaced over the past couple years by PCI Express. AGP cards and motherboards are still available to buy, but they are becoming less common.

AGP Slot

Types Of Cards

Video Card

A video card (also known as graphics card) is an expansion card whose function is to generate and output images to a display. Some video cards offer added functions, such as video capture, TV tuner adapter, ability to connect multiple monitors, and others. Most video cards all share similar components. They include a graphics processing unit (GPU) which is a dedicated microprocessor optimized for 3D graphics rendering. It also includes a video BIOS that contains the basic program that governs the video card’s operations and provides the instructions that allow the computer and software to interface with the card. If the video card is integrated in the motherboard, it may use the computer RAM memory. If it is not it will have its own video memory called Video RAM. This kind of memory can range from 128MB to 2GB. A video card also has a RAMDAC (Random Access Memory Digital-to-Analog Converter) which takes responsibility for turning the digital signals produced by the computer processor into an analog signal which can be understood by the computer display. Lastly, they all have outputs such as an HD-15 connector (standard monitor cable), DVI connector, S-Video, composite video or component video.

Graphics Card

Sound Card

A sound card is an expansion card that facilitates the input and output of audio signals to/from a computer under control of computer programs. Typical uses for sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment. Many computers have sound capabilities built in,, while others require additional expansion cards to provide for audio capability.

Network Card

A network card is an expansion card that allows computers to communicate over a computer network. It allows users to connect to each other either by using cables or wirelessly. Although other network technologies exist, Ethernet has achieved near-ubiquity for a while now. Every Ethernet network card has a unique 48-bit serial number called a MAC address, which is stored in ROM carried on the card. You can learn more about networking in the introduction to networking lesson.

Network Card

External

Types of Connections

USB

USB (Universal Serial Bus) is a serial bus standard to interface devices. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve the plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the computer. Other convient features include providing power to low-consumption devices without the need for an external power supply and allowing many devices to be used without requiring manufacturer specific, individual device drivers to be installed. USB is by far the dominating bus for connecting external devices to your computer.

USB Connectors

Firewire

Firewire (technically known as IEEE 1394 and also known as i.LINK for Sony) is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used in a personal computer. Firewire has replaced Parallel ports in many applications. It has been adopted as the High Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control. Almost all modern digital camcorders have included this connection.

Firewire Cable

PS/2

The PS/2 connector is used for connecting some keyboards and mice to a PC compatible computer system. The keyboard and mouse interfaces are electrically similar with the main difference being that open collector outputs are required on both ends of the keyboard interface to allow bidirectional communication. If a PS/2 mouse is connected to a PS/2 keyboard port, the mouse may not be recognized by the computer depending on configuration.

PS/2 Ports

Devices

Removable Storage

The same kinds of CD and DVD drives that could come built-in on your computer can also be attached externally. You might only have a CD-ROM drive built-in to your computer but you need a CD writer to burn CDs. You can buy an external CD writer that connects to your USB port and acts the same way as if it was built-in to your computer. The same is true for DVD writers, Blu-ray drives, and floppy drives. Flash drives have become very popular forms of removable storage especially as the price of flash drives decreases and the possible size for them increases. Flash drives are usually USB ones either in the form USB sticks or very small, portable devices. USB flash drives are small, fast, removable, rewritable, and long-lasting. Storage capacities range from 64MB to 32GB or more. A flash drive does not have any mechanically driven parts so as opposed to a hard drive which makes it more durable and smaller usually.

USB Flash Drive

Non-removable Storage

Non-removable storage can be a hard drive that is connected externally. External hard drives have become very popular for backups, shared drives among many computers, and simply expaning the amount of hard drive space you have from your internal hard drive. External hard drives come in many shapes and sizes like flash drives do. An external hard drive is usually connected by USB but you can also have a networked hardrive which will connect to your network which allows all computers on that network to access that hard drive.

Input

Input devices are absolutely crucial to computers. The most common input devices are mice and keyboards which barely every computer has. A new popular pointing device that may eventually replace the mouse is touch screen which you can get on some tablet notebooks. Other popular input devices include microphones, webcams, and fingerprint readers which can also be built in to modern laptops and desktops. A scanner is another popular input device that might be built-in to your printer.

Webcam

Output

There are lots of different kinds of output devices that you can get for your computer. The absolute most common external output device is a monitor. Other very popular output devices are printers and speakers. There are lots of different kinds of printers and different sizes of speakers for your computer. Monitors are connected usually through the HD-15 connector on your video card. Printers are usually connected through a USB port. Speakers have their own audio out port built-in to the sound card.

Monitor

ASSESS YOUR KNOWLEDGE

Computer Hardware Peripherals Worksheet: Define Key Terms

TVET TRAINING ICT TRAINING

NTQF Level I

ICT ITS1 01 0710

Connect Hardware

Peripherals

ICT ITS1 02 0710

Install Software

Application

ICT ITS1 03 0710

Record Client Support Requirements

ICT ITS1 04 0710

Protect Application or System Software

ICT ITS1 05 0710

Maintain Equipment and Software Inventory

and Documentation

ICT ITS1 06 0710

Operate Personal Computer

ICT ITS1 07 0710

Apply Quality Standards

ICT ITS1 08 0710

Work with Others

ICT ITS1 09 0710

Receive and Respond to Workplace Communication

ICT ITS1 10 0710

Demonstrate Work Values

For more............

Thursday, March 17

How computer Know Emages?

Image File Formats

Color Representation

True Color (24 bit): each pixel color is represented using 3 bytes, one for red, one for green, and one for blue. This is referred to RGB color. Since a single byte can represent 256 different shades, there are a total of roughly 16 million (256x256x256) colors that can be represented.

True Color (32bit): This is the same as 24 bit true color except that there is an extra byte, usually referred to as the alpha component, used to specify transparency.

16 bit Color: Each pixel is represented using 16 bits or 2 bytes. There are 5 bits for red, 6 bits for green, and 5 bits for blue. The total number of possible colors is about 65 thousand (256x256).

8 bit Color: Here, 256 different 24 bit colors are selected out of the 16 million possible. These 256 colors are called the palette. Each pixel is represented by a single byte. This byte is not the color but is the location of the color in the palette. When an image is stored, the 8 bit color location for each pixel is saved along with the palette. For a large image this can be significant space savings.

Image Representation

Images are represented by by specifying the color of each pixel using one of the above color formats. For large images, the storage space can be very large. As a result, images are usually compressed, meaning that redundancies are removed. For example, suppose a 100x100 pixel image in 24 bit true color happens to be all one color (not a particularly interesting picture). To store it requires 100x100x3 = 30,000 bytes. However, it can also be can be saved very efficiently by specifying the single color (3 bytes) and the size of the image. This format will take on the order of 10's of bytes instead of many thousands.

The following image formats correspond to different method of compressing files.

GIF: Assumes a palette of size 256 colors. If the image has more than 256 colors then there will be some loss of information (called lossy), otherwise, the image will be saved exactly (lossless). GIF allows for images to have transparency. This is useful if one wants the web page background color to show through (e.g. an edge can be faded out). Colors that are thrown out can be approximated using dithering. Dithering is a technique where two existing colors can be placed near each other to give the effect of a third color. Because of the color limit, gif is typically used for images that contain a limited number of colors.

JPEG: JPEG is a lossy format. Once can specify the amount of compression (and thus the amount of information loss) by setting a quality level. Unlike GIF, JPEG is not limited to 256 colors. When an image has many different colors such as in photographs of natural scenes, JPEG is the format of choice. JPEG, however, does not allow for transparency.

PNG: PNG is a more recent file format that is not supported by older browsers. PNG-24 uses 24 bit color, is lossless, and allows transparency. The size of the files can be considerably larger than JPEG. PNG-8 assumes a palette. Like GIF, if the image has a limited number of colors, the compression will be lossless and will be considerably smaller than PNG-24.

There are many other image formats such as Targa, PICT, BMP, .... However, these formats are not supported by any browsers.

For a summary of file formats (not just graphics) click here or here.

General Rule of Thumb:

Use JPEG for images with many colors.
Use GIF if there are a limited number of colors and transparency is desired.
Use PNG-24 is there are many colors and transparency is required.
Photoshop allows you to experiment with the size and quality of the various formats. When in doubt, experiment.
If you want the best resolution and quality of an image then create a thumbnail image of the image and link it to the full image. That way, a user need not spend the time to load in the full image if they are interested.

Hardware Components

External Components:
- System Unit
  - Motherboard, Disks, Network Connection, Power Supply
- Monitor
- Keyboard
- Mouse
Motherboard
- CPU (ALU, control units, registers, See Fritz Ruehr's simulator), memory (cache, RAM, ROM), bus(es), graphics cards, ....
Disks
- Floppy Disk, Hard Disk, CD ROM, DVD, Zip Disks, etc

Memory Hierarchy

Reference webs and books

All computer courses

https://www.willamette.edu/~gorr/classes/cs130/lectures/index.htm

ASCII: What is It and Why Should I Care?

ASCII:
What is It and Why Should I Care?

ASCII, pronounced "ask-ee" is the acronym for American Standard Code for Information Interchange. It's a set of characters which, unlike the characters in word processing documents, allow no special formatting like different fonts, bold, underlined or italic text. All the characters used in email messages are ASCII characters and so are all the characters used in HTML documents. (Web browsers read the ASCII characters between angle brackets, "<" and ">", to interpret how to format and display HTML documents.)

An "ASCII file" is a data or text file that contains only characters coded from the standard ASCII character set. Characters 0 through 127 comprise the Standard ASCII Set and characters 128 to 255 are considered to be in the Extended ASCII Set. These codes, however, may not be the same in all computers and files containing these characters may not display or convert properly by another ASCII program.

Knowing something about ASCII can be helpful. ASCII files can be used as a common denominator for data conversions. For example, if program A can't convert its data to the format of program B, but both programs can input and output ASCII files, the conversion may be possible.

ASCII characters are the ones used to send and receive email. If you're familiar with email, you already know that formatting like italic type and underlines are not possible. Email transmissions are limited to ASCII characters and because of that, graphics files and documents with non-ASCII characters created in word processers, spreadsheet or database programs must be "ASCII-fied" and sent as email file attachments. When the files reach their destination they are "deASCII-fied" (i.e. decoded) and therefore, reconstructed to restore them for use.

Standard ASCII

The first 32 characters (0-31) are control codes.

ASCII		Description
0	NUL	Null
1	SOH	Start of heading
2	STX	Start of text
3	ETX	End of text
4	EOT	End of transmit
5	ENQ	Enquiry
6	ACK	Acknowledge
7	BEL	Audible bell
8	BS	Backspace
9	HT	Horizontal tab
10	LF	Line feed
11	VT	Vertical tab
12	FF	Form feed
13	CR	Carriage return
14	SO	Shift out
15	SI	Shift in
16	DLE	Data link escape
17	DC1	Device control 1
18	DC2	Device control 2
19	DC3	Device control 3
20	DC4	Device control 4
21	NAK	Neg. acknowledge
22	SYN	Synchronous idle
23	ETB	End trans. block
24	CAN	Cancel
25	EM	End of medium
26	SUB	Substitution
27	ESC	Escape
28	FS	Figures shift
29	GS	Group separator
30	RS	Record separator
31	US	Unit separator
32	SP	Blank Space (Space Bar)
ASCII	DISPLAY
33	!
34	"
35	#
36	$
37	%
38	&
39	'
40	(
41	)
42	*
43	+
44	,
45	-
46	.
47	/
48	0
49	1
50	2
51	3
52	4
53	5
54	6
55	7
56	8
57	9
58	:
59	;
60	<
61	=
62	>
63	?
64	@
65	A
66	B
67	C
68	D
69	E
70	F
71	G
72	H
73	I
74	J
75	K
76	L
77	M
78	N
79	O
80	P
81	Q
82	R
83	S
84	T
85	U
86	V
87	W
88	X
89	Y
90	Z
91	[
92	\
93	]
94	^
95	_
96	`
97	a
98	b
99	c
100	d
101	e
102	f
103	g
104	h
105	i
106	j
107	k
108	l
109	m
110	n
111	o
112	p
113	q
114	r
115	s
116	t
117	u
118	v
119	w
120	x
121	y
122	z
123	{
124	\|
125	}
126	~
127

Binary Representation of Numbers

Binary Numbers are numbers represented with 0's and 1's.

They work much the same way as our normal decimal numbers except instead of 10 digits (0 to 9) there are only 2 digits (0 and 1).

Decimal number (subscript indicates base 10):

8401.32

= 8 x 1000 + 4 x 100 + 0 x 10 +

1 x 1 + 3 x 1/10 + 2 x 1/100

= 8 x 10³ + 4 x 10² + 0 x 10¹ + 1 x 10⁰+

3 x 10^-1+ 2 x 10^-2

Binary number (subscript indicates base) :

1101.01₂ = 1 x 8 + 1 x 4 + 0 x 2 + 1 x 1 + 0 x 1/2 + 1 x 1/4

= 1 x 2³ + 1 x 2² + 0 x 2¹ + 1 x 2⁰ + 0 x 2^-1 + 1 x 2^-2

which in base 10 is

110101₂ = 8 + 4 + 1 + 1/4 = 13.25₁₀

Practice: What is 100110.1₂ in base 10?

How do you add numbers in binary?

Representing Negative Integers: 2's Complement

(Integers are whole numbers - there is no decimal component. Note that negative decimal numbers will be treated very differently.)

A bit is either 0 or 1. There is no symbol for "-" so we need a way of representing negative numbers. Suppose we have 4 bits to work with. That gives is 2⁴ = 16 possible combinations. Let's also say we want roughly half to be positive and half to be negative.

One possibility is to have the leftmost bit be 0 if the number is positive and 1 otherwise (sign magnitude). The remaining part of the number will represent the absolute value of the number in standard binary form.

Hex	All Positive	Binary	Sign Magnitude	2's Complement
0 1 2 3 4 5 6 7 8 9 A B C D E F	0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15	0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111	0 1 2 3 4 5 6 7 -0 -1 -2 -3 -4 -5 -6 -7	0 1 2 3 4 5 6 7 -8 -7 -6 -5 -4 -3 -2 -1

An alternative is 2's Complement: Here, negative numbers are obtained as follows:

write magnitude in binary
invert all bits (make sure leading zeros are also inverted)
add 1
Example: -5 assuming 4-bit numbers.
- magnitude: 0101
- invert: 1010
- add 1: 1011

What are advantages of 2's complement over sign magnitude?

In sign magnitude, zero is represented in 2 ways so we have one less number that can be represented. Double representation can also cause problems when comparing numbers; numbers may be the same but look different.
Addition and subtraction are very easy in 2's complement. To compute 6-2, we just add 6 to -2 using normal addition dropping the leftmost carry bit if there is any carry:

0110₂ = 6

1110₂ = -2

---------------

0100₂ = 4

Hexadecimal (Hex) Format

Often we write binary numbers in hex format. This is because

It is very easy to convert between binary and hex
It is a lot easier for a human to read hex than binary because there are many fewer digits.

What is Hex?

Hex is base 16. The "digits" are 0,1,...9,A,B,C,D,E,F.

Examples:

10₁₆ = 16₁₀

CA₁₆ = 12 x 16¹ + 10 x 16⁰ = 202₁₀

Converting between Binary and Hex:

4 bits represent 16 numbers, therefore a single hex digit can be represented by exactly 4 binary digits (see table above).

1110 1010 0010 0001₂ = EA21₁₆

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Computer Hardware Peripherals

Introduction

Buses

Internal

Types of Slots

PCI

PCI Express

PCMCIA

AGP

Types Of Cards

Video Card

Sound Card

Network Card

External

Types of Connections

USB

Firewire

PS/2

Devices

Removable Storage

Non-removable Storage

Input

Output

NTQF Level I

Thursday, March 17

Image File Formats

Color Representation

Image Representation

Memory Hierarchy

ASCII:What is It and Why Should I Care?

Binary Representation of Numbers

Decimal number (subscript indicates base 10):

Binary number (subscript indicates base) :

Representing Negative Integers: 2's Complement

Hexadecimal (Hex) Format

ASCII:
What is It and Why Should I Care?