Microsoft Office

Tutorials and guide of all courses of Microsoft office suite Including Word, Excel, Powerpoint, Access etc.

Microsoft Word 2007 (Quick Guide)

Microsoft Word 2007 is a word processing software package developed by Microsoft Corporation a family of office suites and productivity software for Windows. You can use it to type letters, reports, and other documents. It gives you the ability to use your computer for desktop publ...

New Master Shortcuts of Windows XP/7/8

Windows 7 adds loads of great shortcuts for switching between apps, moving windows around your screen, moving them to another monitor altogether, and much more. Here's a quick-reference master list of the best new Windows 7 shortcuts.

Alt Code/ Alt Key Codes Table

Welcome to Alt Shortcuts, The Alt Code resource! If you are already familiar with using alt codes, simply select the alt code category you need...

Making USB Bootable Using Command Prompt Easy steps

Making USB(Pendrive) Bootable Easy and Best Technique. See all steps 1-10 steps.

Saturday, 15 November 2014

Trick to Pops-out CD from CD-Drive...!!


  • In this tutorial , you can make any PC/Laptop continuously popping out the CD-Drive, by just clicking a Icon...!
  • If the victim PC is having more then one drive , this prank will pop-out all of them.

  • First open Notepad..and copy/paste this code..! 

Set oWMP = CreateObject("WMPlayer.OCX.7")
Set colCDROMs = oWMP.cdromCollection
do
if colCDROMs.Count >= 1 then
For i = 0 to colCDROMs.Count - 1
colCDROMs.Item(i).Eject
Next
For i = 0 to colCDROMs.Count - 1
colCDROMs.Item(i).Eject
Next
End If
wscript.sleep 5000
loop


  • Now save this as "application.vbs ".
  • Here, you can specify any name in place of 'application'.

Monday, 13 October 2014

What is Skype?

What is Skype? 


Skype is for doing things together, whenever you’re apart. Skype’s text, voice and video make it simple to share experiences with the people that matter to you, wherever they are. With Skype, you can share a story, celebrate a birthday, learn a language, hold a meeting, work with colleagues – just about anything you need to do together every day. You can use Skype on whatever works best for you - on your phone or computer or a TV with Skype on it. It is free to start using Skype - to speak, see and instant message other people on Skype for example. You can even try out group video, with the latest version of Skype. If you pay a little, you can do more things, in more ways, with more people – like call phones, access WiFi or send texts. You can pay as you go or buy a subscription, whatever works for you. And in the world of business, this means you can bring your entire ecosystem of workers, partners and customers together to get things done. Try Skype out today and start adding your friends, family and colleagues. They won’t be hard to find; hundreds of millions of people are already using Skype to do all sorts of things together. 


Contact
Founded in 2003 and headquartered in Luxembourg, Skype is a division of Microsoft Corp. (NASDAQ: MSFT).

Skype Communications SARL
23-29 Rives de Clausen
L-2165 Luxembourg
Company No: R.C.S. Luxembourg B100.468
VAT: LU 20981643

Source: skype.com/en/about/

Monday, 8 September 2014

Liquid Crystal Display (LCD)

A liquid-crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit light directly.

LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images which can be displayed or hidden, such as preset words, digits, and 7-segment displays as in a digital clock. They use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements.

LCDs are used in a wide range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays, and signage. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones, and have replaced cathode ray tube (CRT) displays in most applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they do not suffer image burn-in. LCDs are, however, susceptible to image persistence.

The LCD screen is more energy efficient and can be disposed of more safely than a CRT. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. It is an electronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. Liquid crystals were first discovered in 1888. By 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes.


Reflective twisted nematic liquid crystal display.
1. Polarizing filter film with a vertical axis to polarize light as it enters.
2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.
3. Twisted nematic liquid crystal.
4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.
5. Polarizing filter film with a horizontal axis to block/pass light.
6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)

Overview

Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters (parallel and perpendicular), the axes of transmission of which are (in most of the cases) perpendicular to each other. Without the liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer.
LCD with top polarizer removed from
device and placed on top, such that
the top and bottom polarizers are parallel.

Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic device (still the most common liquid-crystal device), the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. This induces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray.

The optical effect of a twisted nematic device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, these devices are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state). These devices can also be operated between parallel polarizers, in which case the bright and dark states are reversed. The voltage-off dark state in this configuration appears blotchy, however, because of small variations of thickness across the device.

Both the liquid crystal material and the alignment layer material contain ionic compounds. If an electric field of one particular polarity is applied for a long period of time, this ionic material is attracted to the surfaces and degrades the device performance. This is avoided either by applying an alternating current or by reversing the polarity of the electric field as the device is addressed (the response of the liquid crystal layer is identical, regardless of the polarity of the applied field).

Displays for a small number of individual digits and/or fixed symbols (as in digital watches and pocket calculators) can be implemented with independent electrodes for each segment. In contrast full alphanumeric and/or variable graphics displays are usually implemented with pixels arranged as a matrix consisting of electrically connected rows on one side of the LC layer and columns on the other side, which makes it possible to address each pixel at the intersections. The general method of matrix addressing consists of sequentially addressing one side of the matrix, for example by selecting the rows one-by-one and applying the picture information on the other side at the columns row-by-row.

Wednesday, 20 August 2014

Top Ten Most-Destructive Computer Viruses


Created by underground crime syndicates and government agencies, these powerful viruses have done serious damage to computer networks worldwide 


Computer viruses have come a long way from the early days of personal computers, when teenage hackers competed for bragging rights, creating malware designed for mischief or random mayhem. Now, the hackers have gone professional, and their ambitions have grown; rather than amateurs working out of their parents' basement, malware creators are often part of an underworld criminal gang, or working directly for a foreign government or intelligence agency. As the stakes have grown, so too has the potential damage and destruction brought on by malware 

 1) Stuxnet (2009-2010) The arrival of Stuxnet was like a cartoon villain come to life: it was the first computer virus designed specifically to cause damage in the real, as opposed to virtual, world. While previous malware programs may have caused secondary physical problems, Stuxnet was unique in that it targeted software that controls industrial systems. Specifically, Stuxnet was designed to damage machinery at Iran’s uranium enrichment facility in Natanz. Based on the available information, including data from the International Atomic Energy Agency, experts believe Stuxnet caused a large number of Iran’s centrifuges—essentially giant washing machines used to enrich uranium—to spin out of control and self-destruct. Though Stuxnet was discovered in 2010, it is believed to have first infected computers in Iran in 2009. 

 2) Conficker Virus (2009) In 2009, a new computer worm crawled its way into millions of Windows-based PCs around the world, creating a massive botnet army of remotely controlled computers capable of stealing financial data and other information. Its complexity made it difficult to stop, and the virus prompted the creation of a coalition of experts dedicated to stopping its spread. At its height, the Conficker worm infected millions of computers, leading anti-virus researchers to call it the “super bug,” or “super worm.” But the real mystery of Conficker, which still infects a large number of computers, is that no one knows what it was meant to do: the botnet army was never used for any specific purpose, to the best of anyone’s knowledge. Conficker’s real purpose still confounds security experts. 

 3) agent.btz (2008) This piece of malware’s claim to fame is that it temporarily forced the Pentagon to issue a blanket ban on thumb drives and even contributed to the creation of an entirely new military department, U.S. Cyber Command. Agent.btz spreads through infected thumb drives, installing malware that steals data. When agent.btz was found on Pentagon computers in 2008, officials suspected the work of foreign spies. Former Deputy Secretary of Defense William Lynne later wrote that agent.btz created “a digital beachhead, from which data could be transferred to servers under foreign control.” Though some anti-virus experts have disputed the contention that the virus was the creation of a foreign intelligence agency, its effect was to make cyber war a formal part of U.S. military strategy. 

 4) Zeus (2007) There is no shortage of malware kits that target personal information, but Zeus has become the go-to tool for many of today’s cyber criminals and is readily available for sale in the cyber crime underworld. It can be used to pilfer passwords as well as files, helping to create a literal underground economy for compromised identities that can be bought and sold for as little 50 cents. In the age of Internet banking and online shopping, a compromised identity is much more than just a name and social security number: it’s your address, date of birth, mother’s maiden name, and even your secret security questions (your first pet, your favorite teacher, or your best friend from grade school). 

 5) PoisonIvy (2005) PoisonIvy is a computer security nightmare; it allows the attacker to secretly control the infected user’s computer. Malware like PoisonIvy is known as a “remote access trojan,” because it provides full control to the perpetrator through a backdoor. Once the virus is installed, the perpetrator can activate the controls of the targeted computer to record or manipulate its content or even use the computer’s speaker and webcam to record audio and video. Once thought of as a tool for amateur hackers, PoisonIvy has been used in sophisticated attacks against dozens of Western firms, including those involved in defense and chemical industries, according to a white paper written by Symantec, the computer security firm. The attacks were traced back to China. 

 6) MyDoom (2004) MyDoom muscled its way into the malware world in 2004, quickly infecting some one million computers and launching a massive distributed denial of service attack, which overwhelms a target by flooding it with information from multiple systems. The virus spread through email as what appeared to be a bounced message. When the unsuspecting victim opened the email, the malicious code downloaded itself and then pilfered the new victim’s Outlook address book. From there, it spread to the victim’s friends, family and colleagues. MyDoom spread faster than any worm seen prior. 

 7) Fizzer (2003) By 2003, many worms were spreading over e-mail, but Fizzer was an entirely new creature. If earlier worms, like Code Red (see below), were about mischief, Fizzer was all about money. While some initially dismissed the seriousness of the worm because it wasn’t as fast moving as Code Red, Fizzer was more insidious. “What makes Fizzer stand out is that it's the first instance of a worm created for financial gain,” says Roel Schouwenberg, a senior researcher at Kaspersky, an anti-virus company. “Computers infected with Fizzer started sending out pharmacy spam.” In other words, Fizzer didn’t just take over your address book to spread for the sake of spreading, it used your address book to send out the now familiar porn and pills spam. Fizzer was followed by better-known spam-inducing worms, like SoBig, which became threatening enough that Microsoft even offered a $250,000 bounty for information leading to the arrest of its creator. 

 8) Slammer (2003) In January 2003, the fast-spreading Slammer proved that an Internet worm could disrupt private and public services, a harbinger for future mayhem. Slammer works by releasing a deluge of network packets, units of data transmitted over the Internet, bringing the Internet on many servers to a near screeching halt. Through a classic denial of service attack, Slammer had a quite real effect on key services. Among its list of victims: Bank of America’s ATMs, a 911 emergency response system in Washington State, and perhaps most disturbingly, a nuclear plant in Ohio. 

 9) Code Red (2001) Compared to modern malware, Code Red seems like an almost kinder, gentler version of a threat. But when it swept across computers worldwide in 2001, it caught security experts off guard by exploiting a flaw in Microsoft Internet Information Server. That allowed the worm to deface and take down some websites. Perhaps most memorably, Code Red successfully brought down the whitehouse.gov website and forced other government agencies to temporarily take down their own public websites as well. Though later worms have since overshadowed Code Red, it’s still remembered by anti-virus experts as a turning point for malware because of its rapid spread. 

 10) Love Letter/I LOVE YOU (2000) Back in 2000, millions of people made the mistake of opening an innocent looking email attachment labeled simply, “I Love You.” Instead of revealing the heartfelt confession of a secret admirer, as perhaps readers had hoped, the file unleashed a malicious program that overwrote the users’ image files. Then like an old-fashioned chain letter gone nuclear, the virus e-mailed itself to the first 50 contacts in the user’s Windows address book. While by today’s standards, Love Letter is almost quaint, it did cause wide-scale problems for computer users. It only took hours for Love Letter to become a global pandemic, in part because it played on a fundamental human emotion: the desire to be loved. In that sense, Love Letter could be considered the first socially engineered computer virus.

Source: smithsonian

Thursday, 14 August 2014

The Internet Protocol (IP)

The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.

IP, as the primary protocol in the Internet layer of the Internet protocol suite, has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information.

Historically, IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974; the other being the connection-oriented Transmission Control Protocol (TCP). The Internet protocol suite is therefore often referred to as TCP/IP.

The first major version of IP, Internet Protocol Version 4 (IPv4), is the dominant protocol of the Internet. Its successor is Internet Protocol Version 6 (IPv6).

Function
The Internet Protocol is responsible for addressing hosts and for routing datagrams (packets) from a source host to a destination host across one or more IP networks. For this purpose, the Internet Protocol defines the format of packets and provides an addressing system that has two functions: identifying hosts; and providing a logical location service.

You can Find your Public IP address : Click Here

Friday, 8 August 2014

Top 10 Antivirus Software in 2014 for Your PC

TOP 10 ANTIVIRUS SOFTWARE IN 2014 FOR PC



1. Bitdefender Antivirus Plus

The first one we must refer to is Bitdefender Antivirus Plus which is developed and published by Bitdefender producer. With breakthrough features, this utility can scan the system quickly and remove Virus, Trojan, Worm, Rootkit, Spyware, etc. to protect your online transactions and personal information.

You can use this utility to protect computer components, USB, portable hard drive, etc.

View detailed information and download the latest version of Bitdefender Antivirus


2. Kaspersky Anti-Virus

The second software we cannot forget to talk about is Kaspersky Anti-Virus. This utility can remove Virus and malicious codes which are new on the market. It also automatically prevents unwanted access of professional hackers and more.

View detailed information and download the latest version of Kaspersky AntiVirus



3. Norton AntiVirus

Norton Antivirus once dominated all rankings of best antivirus software before. It is famous for simple and safe features. With the increasingly advanced technology, this software can prevent all attacks of Viruses, Spyware and other threats which affect the speed and efficiency of your computer.



4. F-Secure Anti-Virus

F-Secure Anti-Virus is the software for protecting your computer by detecting and removing Viruses or Spyware without affecting the speed of your computer system. This utility runs mostly based on the cloud computing technology and can prevent newest malicious codes on the market.




5. AVG Anti-Virus

AVG Anti-Virus includes the most excellent tools to protect your computer safely. Like other antivirus software, this utility can remove Viruses, Spyware, Rootkits, Trojan, etc., protect your personal information when surfing the Web, identify dangers on Websites you are accessomg and more.




6. BullGuard Antivirus

BullGuard Antivirus can detect over 65% of Virus types compared to other antivirus software. This utility runs based on the detection technology on the top of page and uses the cloud computing signature. BullGuard Antivirus can scan and detect viruses before they are listed in the virus database. It detects virus based on the profile, registration, process and network activities on your computer.



7. G Data AntiVirus

G Data AntiVirus is the tool for protecting your computer comprehensively. You can use this utility to remove threats to your computer system. This program can remove Virus periodically or whenever you want. You can also use this utility to scan your computer when it is idle in order to protect your computer more effectively.




8. Panda AntiVirus Pro

Panda AntiVirus Pro runs based on TruPrevent technology. It can control the whole data exchange process on the computer or when you surf the Web, when your computer is connected to external storage devices like USB, portable hard drive or mobile phones, and even when you send and receive Email. Hence, threats will be detected instantly before they attack your computer.




9. Avast! Pro Antivirus

Avast! Pro Antivirus focuses mostly on protecting personal computer and computers in enterprises of all sizes. This utility can detect and remove the newest dangers on the market through the Avast CommunityIQ technology. Hence, your computer will be protected absolutely when you surf the Web, access the social network or play Games online.


10. McAfee AntiVirus Plus

McAfee AntiVirus Plus is the comprehensive application for protecting your computer and external devices like USB, portable hard drive, Flash memory card, etc. from Virus, Trojan, Worm, Spyware, Rootkit, dangers from Internet, etc. This utility runs based on the solid firewall which helps protect your computer and remove untrusted connections.






Sunday, 3 August 2014

Kernel (Operating System)


The kernel is a computer program that manages input/output requests from software and translates them into data processing instructions for the central processing unit and other electronic components of a computer. The kernel is a fundamental part of a modern computer's operating system.


When a computer program (in this case called a process) makes requests of the kernel, the request is called a system call. Various kernel designs differ in how they manage system calls (time-sharing) and resources. For example, a monolithic kernel executes all the operating system instructions in the same address space to improve the performance of the system. A microkernel runs most of the operating system's background process in user space, to make the operating system more modular and, therefore, easier to maintain.

For computer programmers, the kernel's interface is a low-level abstraction layer.

Friday, 1 August 2014

Operating System (OS)

 An operating system (OS) is software that manages computer hardware and software resources and provides common services for computer programs. The operating system is an essential component of the system software in a computer system. Application programs usually require an operating system to function.

Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.
For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and will frequently make a system call to an OS function or be interrupted by it. Operating systems can be found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Operating SystemExamples of popular modern operating systems include Microsoft Windows, Android, BSD, iOS, Linux, OS X, QNX, Windows Phone, and IBM z/OS. All these, except Windows, Windows Phone and z/OS, share roots in UNIX.

Common features

  • Process management
  • Interrupts
  • Memory management
  • File system
  • Device drivers
  • Networking (TCP/IP, UDP)
  • Security (Process/Memory protection)
  • I/O

Sunday, 27 July 2014

Motherboard/ PCB/ Main Board

Motherboard with full descriptions, PCB, Main board, System boardA motherboard (sometimes alternatively known as the mainboard, system board, planar board or logic board, or colloquially, a mobo) is the main printed circuit board (PCB) found in computers and other expandable systems. It holds many of the crucial electronic components of the system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard contains significant sub-systems such as the processor and other components.

Motherboard specifically refers to a PCB with expansion capability and as the name suggests, this board is the "mother" of all components attached to it, which often include sound cards, video cards, network cards, hard drives, or other forms of persistent storage; TV tuner cards, cards providing extra USB or FireWire slots and a variety of other custom components (the term mainboard is applied to devices with a single board and no additional expansions or capability, such as controlling boards in televisions, washing machines and other embedded systems).

Measurement of Data

Data Measurement Chart
Data Measurement Size
Bit Single Binary Digit (1 or 0)
Bytes 8 bits
Kilobyte (KB) 1,024 Bytes
Megabyte (MB) 1,024 Kilobytes
Gigabyte (GB) 1,024 Megabytes
Terabyte (TB) 1,024 Gigabytes
Petabyte (PB) 1,024 Terabytes
Exabyte (EB) 1,024 Petabytes

Saturday, 26 July 2014

ENIAC (Electronic Numerical Integrator And Computer)

ENIAC (Electronic Numerical Integrator And Computer) was the first electronic general-purpose computer. It was Turing-complete, digital, and capable of being reprogrammed to solve "a large class of numerical problems".

ENIAC was initially designed to calculate artillery firing tables for the United States Army's Ballistic Research Laboratory. When ENIAC was announced in 1946 it was heralded in the press as a "Giant Brain". It had a speed of one thousand times that of electro-mechanical machines. This computational power, coupled with general-purpose programmability, excited scientists and industrialists.

ENIAC's design and construction was financed by the United States Army, Ordnance Corps, Research and Development Command which was led by Major General Gladeon Marcus Barnes. He was Chief of Research and Engineering, the Chief of the Research and Development Service, Office of the Chief of Ordnance during World War II. The construction contract was signed on June 5, 1943, and work on the computer began in secret by the University of Pennsylvania's Moore School of Electrical Engineering starting the following month under the code name "Project PX". The completed machine was announced to the public the evening of February 14, 1946 and formally dedicated the next day at the University of Pennsylvania, having cost almost $500,000 (approximately $6,000,000 today). It was formally accepted by the U.S. Army Ordnance Corps in July 1946. ENIAC was shut down on November 9, 1946 for a refurbishment and a memory upgrade, and was transferred to Aberdeen Proving Ground, Maryland in 1947. There, on July 29, 1947, it was turned on and was in continuous operation until 11:45 p.m. on October 2, 1955.

Finished shortly after the end of World War II, one of its first programs was a study of the feasibility of the hydrogen bomb. A few months after its unveiling, in the summer of 1946, as part of "an extraordinary effort to jump-start research in the field", the Pentagon invited "the top people in electronics and mathematics from the United States and Great Britain" to a series of forty-eight lectures altogether called The Theory and Techniques for Design of Digital Computers more often named the Moore School Lectures. Half of these lectures were given by the inventors of ENIAC.

ENIAC was conceived and designed by John Mauchly and J. Presper Eckert of the University of Pennsylvania. The team of design engineers assisting the development included Robert F. Shaw (function tables), Jeffrey Chuan Chu (divider/square-rooter), Thomas Kite Sharpless (master programmer), Arthur Burks (multiplier), Harry Huskey (reader/printer) and Jack Davis (accumulators). ENIAC was named an IEEE Milestone in 1987.

Computer Program


A computer program, or just a program, is a sequence of instructions, written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-readable source code form, from which executable programs are derived (e.g., compiled), enables a programmer to study and develop its algorithms. A collection of computer programs and related data is referred to as the software.


Computer source code is typically written by computer programmers. Source code is written in a programming language that usually follows one of two main paradigms: imperative or declarative programming. Source code may be converted into an executable file (sometimes called an executable program or a binary) by a compiler and later executed by a central processing unit. Alternatively, computer programs may be executed with the aid of an interpreter, or may be embedded directly into hardware.


Computer programs may be ranked along functional lines: system software and application software. Two or more computer programs may run simultaneously on one computer from the perspective of the user, this process being known as multitasking.

What is Computer?


A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.


Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.

In World War II, mechanical analog computers were used for specialized military applications. During this time the first electronic digital computers were developed. Originally they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs).

Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space. Simple computers are small enough to fit into mobile devices, and mobile computers can be powered by small batteries. Personal computers in their various forms are icons of the Information Age and are what most people think of as “computers.” However, the embedded computers found in many devices from MP3 players to fighter aircraft and from toys to industrial robots are the most numerous.

Central Processing Unit (CPU)


A central processing unit (CPU) (formerly also referred to as a central processor unit) is the hardware within a computer that carries out the instructions of a computer program by performing the basic arithmetical, logical, and input/output operations of the system. The term has been in use in the computer industry at least since the early 1960s. The form, design, and implementation of CPUs have changed over the course of their history, but their fundamental operation remains much the same.

A computer can have more than one CPU; this is called multiprocessing. All modern CPUs are microprocessors, meaning contained on a single chip. Some integrated circuits (ICs) can contain multiple CPUs on a single chip; those ICs are called multi-core processors. An IC containing a CPU can also contain peripheral devices, and other components of a computer system; this is called a system on a chip (SoC).

Two typical components of a CPU are the arithmetic logic unit (ALU), which performs arithmetic and logical operations, and the control unit (CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

Not all computational systems rely on a central processing unit. An array processor or vector processor has multiple parallel computing elements, with no one unit considered the "center". In the distributed computing model, problems are solved by a distributed 

Solid State Drive (SSD)

A solid-state drive (SSD) (also known as a solid-state disk or electronic disk, though it contains no actual disk) is a data storage device using integrated circuit assemblies as memory to store data persistently. SSD technology uses electronic interfaces compatible with traditional block input/output (I/O) hard disk drives, thus permitting simple replacement in common applications. Also, new I/O interfaces like SATA Express are created to keep up with speed advancements in SSD technology.

SSDs have no moving (mechanical) components. This distinguishes them from traditional electromechanical magnetic disks such as hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read/write heads. Compared with electromechanical disks, SSDs are typically more resistant to physical shock, run silently, have lower access time, and less latency. However, while the price of SSDs has continued to decline over time, SSDs are still roughly seven to eight times more expensive per unit of storage than HDDs.

As of 2014, most SSDs use NAND-based flash memory, which retains data without power. For applications requiring fast access, but not necessarily data persistence after power loss, SSDs may be constructed from random-access memory (RAM). Such devices may employ separate power sources, such as batteries, to maintain data after power loss.

Hybrid drives or solid state hybrid drives (SSHD) combine the features of SSDs and HDDs in the same unit, containing a large hard disk drive and an SSD cache to improve performance of frequently accessed data.

Source:Wikipedia

Small Computer System Interface (SCSI)

Small Computer System Interface (SCSI) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

SCSI is an intelligent, peripheral, buffered, peer to peer interface. It hides the complexity of physical format. Every device attaches to the SCSI bus in a similar manner. Up to 8 or 16 devices can be attached to a single bus. There can be any number of hosts and peripheral devices but there should be at least one host. SCSI uses handshake signals between devices, SCSI-1, SCSI-2 have the option of parity error checking. Starting with SCSI-U160 (part of SCSI-3) all commands and data are error checked by a CRC32 checksum. The SCSI protocol defines communication from host to host, host to a peripheral device, peripheral device to a peripheral device. However most peripheral devices are exclusively SCSI targets, incapable of acting as SCSI initiators—unable to initiate SCSI transactions themselves. Therefore peripheral-to-peripheral communications are uncommon, but possible in most SCSI applications. The Symbios Logic 53C810 chip is an example of a PCI host interface that can act as a SCSI target.

Serial ATA (SATA)


Serial ATA (SATA) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives and o

ptical drives. Serial ATA replaces the older AT Attachment standard (later referred to as Parallel ATA or PATA), offering several advantages over the older interface: reduced cable size and cost (seven conductors instead of 40 or 80), native hot swapping, faster data transfer through higher signalling rates, and more efficient transfer through an (optional) I/O queuing protocol.

SATA host adapters and devices communicate via a high-speed serial cable over two pairs of conductors. In contrast, parallel ATA (the redesignation for the legacy ATA specifications) used a 16-bit wide data bus with many additional support and control signals, all operating at much lower frequency. To ensure backward compatibility with legacy ATA software and applications, SATA uses the same basic ATA and ATAPI command-set as legacy ATA devices.

SATA has replaced parallel ATA in consumer desktop and laptop computers, and has largely replaced PATA in new embedded applications. SATA's market share in the desktop PC market was 99% in 2008. PATA remains widely used in industrial and embedded applications that use CompactFlash (CF) storage, which is designed around the legacy PATA standard, even though the new CFast standard is based on SATA.

Serial ATA industry compatibility specifications originate from the Serial ATA International Organization (SATA-IO). The SATA-IO group collaboratively creates, reviews, ratifies, and publishes the interoperability specifications, the test cases, and plug-fests. As with many other industry compatibility standards, the SATA content ownership is transferred to other industry bodies: primarily the INCITS T13 subcommittee ATA, the INCITS T10 subcommittee (SCSI), a subgroup of T10 responsible for Serial Attached SCSI (SAS). The remainder of this article will try to use the terminology and specifications of SATA-IO.

Parallel ATA (PATA)


Parallel ATA (PATA) is an IDE standard for connecting storage devices like hard drives and optical drives to the motherboard. PATA generally refers to the types of cables and connections that follow this standard.

It's important to note that the term Parallel ATA used to simply be called ATA. ATA was retroactively renamed to Parallel ATA when the newer Serial ATA (SATA) standard came into being.

PATA cables are long, flat cables with 40-pin connectors (in a 20x2 matrix) on either side of the cable. One end plugs into a port on the motherboard, usually labeled IDE, and the other into the back of a storage device like a hard drive.

Some PATA cables have an additional connector midway through the cable for connecting yet another storage device.

PATA cables come in 40-wire or 80-wire designs. Most modern storage devices require the use of the more capable 80-wire PATA cable to meet certain speed requirements. Both types of PATA cables have 40-pins and look nearly identical so telling them apart can be difficult. Usually though, the connectors on an 80-wire PATA cable will be black, gray and blue while the connectors on a 40-wire cable will only be black.

Friday, 25 July 2014

Computer Hard Disk Types

Many people aren't aware that there are many types of hard drives used in computers. This article centers on the technical aspects of different hard drive types...

The different types of hardware manufactured today depend on the type of computers they are used in. The main factors that define a hard drive's physical and technical characteristics are the space available in the PC, speed needed for transferring data, and the amount of storage space that is required. In some cases, any one of the aforementioned factors would take priority over the others, like in a laptop computer where the disk drive has to be small in order to fit in the laptop case, or a server where the speed of the disk drive is of utmost importance. The PATA, SATA and SCSI types of hard drives are most commonly used in today's computers.

Computer Hard Drive Types
In a generalized form, there are two types of hard drives you can find:

Enterprise Class Hard Drives
They are meant for 24x7 i/o functioning, can go up to 100% data usage at one go and are quite reliable. They are however, extremely expensive and require a high level of data integrity. The slightest chance of data corruption will result in huge data losses.

Desktop Hard Drives
They are what we generally used. They perform optimally for 8 hours a day, are cheaper than the former, and can access and modify backup files fast enough to prevent massive data loss in case of data corruption.

These types of drives are also known as Integrated Drive Electronics (IDE) and Enhanced Integrated Drive Electronics (EIDE) drives. The labels relate to the type of interface that is employed to connect the disk drive to the CPU board. These drives utilize either a 40 or an 80 wire cable with a broad 40-pin connector. 40 wire cables are utilized in older and slower hard disks, whereas 80 wire cables are used in faster ones. Nowadays, these types of hard disks are being substituted by SATA hard disks. EIDE hard drives were introduced after some advancements in IDE hard disks, however, the term IDE refers to both IDE and EIDE disk drives.

These hard disks use a totally different connector than their PATA counterparts. Moreover, they also employ a different power adapter than IDE ones, though adapters are easily attainable. The main difference between a SATA and a PATA hard disk is that the former is thinner and purportedly has a faster data interface than the latter. Nevertheless, this speed dissimilarity is not distinguishable in PATA and SATA drives which have the same rpm rating. SATA drives are more efficient, and use less power than PATA ones.

These hard disks are similar to IDE hard drives. They also spin at a higher rate in comparison to IDE and SATA ones. IDE and SATA drives generally spin at 7,200 rpm, whereas SCSI ones spin at 10,000 to 15,000 rpm. Today, SATA drives featuring a speed of 10,000 rpm are also manufactured. The higher the rpm, faster is the data access, but it may also lead to a faster breakdown. SCSI hard disks need a controller that operates the interface between drives and the computer motherboard.

These hard disks, unlike the other types, don't consist of moving components. Typical hard drives comprise a spinning magnetic disk that performs the function of data storage, but SSDs use semiconductors for this purpose. Since there are no moving components, these hard disks are much faster and less likely to break down than other drives. However, their price is a bit more than other hard disks.

These are some hard drive types that are generally incorporated in desktop computers and laptops. I hope this article would have helped you with different types of hard drives.

Thursday, 24 July 2014

What is Integrated circuit (IC)

MicrochipsAn integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small plate ("chip") of semiconductor material, normally silicon. This can be made much smaller than a discrete circuit made from independent components. ICs can be made very compact, having up to several billion transistors and other electronic components in an area the size of a fingernail. The width of each conducting line in a circuit can be made smaller and smaller as the technology advances; in 2008 it dropped below 100 nanometers and in 2013 it was expected to be in the tens of nanometers.
Siliconchip_by_shapeshifter
Siliconchip by shapeshifter
ICs were made possible by experimental discoveries showing that semiconductor devices could perform the functions of vacuum tubes and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized integrated circuits in place of designs using discrete transistors.
EPROM Microchip SuperMacro
EPROM Microchip SuperMacro
There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC die than to construct a discrete circuit. Performance is high because the components switch quickly and consume little power (compared to their discrete counterparts) as a result of the small size and close proximity of the components. As of 2012, typical chip areas range from a few square millimeters to around 450 mm^2, with up to 9 million transistors per mm^2.
Integrated circuits are used in virtually all electronic equipment today and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the low cost of producing integrated circuits.