Basic Computer Terms You Should Know Before Buying A PC

Basic Computer Terms You Should Know Before Buying a PC

Have you decided to get rid of that old paperweight and buy yourself a new computer? Good for you but before you go running out to buy the latest and greatest machine, there are some basic computer terms you should know. We will run through each of these terms for you and what they mean.

The terminology used below is the same for PCs and Macs and for desktops and laptops. If you have any doubts about the machine you are buying. don’t buy it! Go and do some research online to see if you can do better
When you are looking to buy a computer you will hear basic computer terms like the following:

The Processor

This is the brain of your computer. It can also be referred to as the CPU. Processors come in many different varieties. Processor speed is termed as clock speed measured in gigahertz or GHz. more the value of GHZ the faster the computer.
I am now using a 3.06 GHz  Intel^®  dual core^TM  i3 processor. Processors can also have dual or quad cores. This is essentially two or four processors in one respectively. The more cores the better but they will also be more expensive. We will also see terms like Core Duo, Core 2 Duo, i3, i5, and i7. It is important to know the differences between these options.
The Core Duo consists of two cores on one die but the Core 2 Duo is a more modern processor that is found in a lot of new PCs. the Core 2 Duo has two dies. Then the i3 processor is a recent release by Intel for new home machines. Then the i5 and i7 are used with quad core processors and higher end machines. The i7 is the top of this line and obviously the most expensive.
There are different brands of processors like Intel or AMD and different levels of processors like the Pentium 4 or the Atom. The Atom processor is a much slower processor used in notebooks.

The RAM

The RAM or memory is what your computer uses to store information while you are using the computer. I am using Transcend 4 GB DDR3 Ram .This can also be referred to as Random Access Memory. I personally would not buy a computer with less than 2 GB of RAM. Your RAM Bus speed will need to be identical to your FSB speed as to not create bottlenecks. In a pre-built system this is not something you need to worry about but if you are building your own system then you will want to get memory that matches the FSB speed divided by the number of cores that you have. For example if your system has a total FSB of 1600 and you have 4 cores (quad) then your RAM Bus speed should be 400 MHz.

Optical Drive

The optical drive in your computer should be able to read and write CDs and DVDs. If you have not purchased a computer in a while some of the newer options might seem strange to you. You can have any one of these or a combination of these formats: DVD-R, DVD+R, DVD-+R, DVD-/+RW, DVD-RAM, Blu-ray, HD-DVD. A CD holds 700 MB. A CD-R can read and write to a CD. A CDRW can read write and rewrite to a CD.
If you are getting a DVD burner you should try and get a drive that writes in all formats such as +R or -R. They will all play in your computer but some other hardware might require one of these formats. A DVD can hold About 4 GB of data. A DVD burner that allows you to burn a DL or dual layer will allow for double the capacity and can fit about 8 GB of data on it. A dual layer drive is required as well as dual layered media.
Then we see the newer formats like Blu-Ray and HD-DVD that allow you to burn and watch high definition videos or store even more data. A Blu-Ray disk can hold a whopping 25 GB in a single layer and 50 GB if the disk is dual layered. HD-DVD disks can hold up to 15 GB of data but I really do not see many systems or people using this format.

Wireless Network Card

If your computer has a wireless card you will be able to access the Internet without a wire connecting you to a router/modem. Wireless cards are rated by their speed.
The lowest speed starts from A and goes up through N. You will want to buy a computer with a 802.11G or 802.11N wireless connection. 802.11g can see speeds of up to 54 Mbit/s. And with 802.11n the newest iteration of wireless we can achieve 600 Mbit/s. I am using a 802.11n router personally but most of my equipment and peripherals use 802.11g. I find this to be fine for streaming video or audio and transferring files over my home network. But if you are constantly transferring huge files or folders you might want to jump right into the 802.11n game.

Network Card

Your computer should have an Ethernet port on it. This port will allow you to physically connect to the internet or your internal network by plugging it into your router / modem.
Normally any machine you will buy now has a Gigabit connection. Gigabit is represented as 100/1000 and there are also 10/100 connections. That number is how many megabits you can transfer per second.

Operating System

This is the software that makes your computer go. You can buy a computer with the Windows 7 or 8 any flavor of Ubuntu Linux as well. Windows 8 is good for touch screen pc. You can choose windows 7. Different versions are home premium, home basic, professional, Ultimate. I am using windows 7 ultimate.
You can also buy a computer without an operating system to install it yourself. This is the key part of your system as well as normally the most expensive. But, if you choose Ubuntu or another flavor of Linux then your operating system is free.

Hard Drive

This is where you will store all your files whether it be music, movies or word documents. You will need a hard drive to store them on.
Seagate and WD (Western Digitals) are most famous companies and are good.
Hard drives are rated by size and speed. These are available in two different speed, that is 7200RPM and 5400 RPM. More the speed of HDD you can access fast.
If you need more space you should get a bigger drive or you can buy a portable USB hard drive to attach to your computer. Normally 500GB is used maximum 1TB is used..

Video Card

 

This is the part of your computer that allows you to show what you are doing. Without a video card you would not be able to see what you are doing on your monitor. Normally it is already built-in in mother board. 
Different video cards have different abilities like the option to use multiple monitors, have a HDMI output or even the ability to watch HD movies on your computer. This has never been important to me and I always take whatever is available. Some examples of good video card brands are MSI, XFX, Asus, Gigabyte.
Your video card does have to connect to your monitor so make sure they have a VGA, DVI or HDMI port in common.
There are also computer components like the monitor, keyboard and mouse but we’re pretty sure that you’re familiar with those basic computer terms.
Now, you have a basic knowledge of what you are looking for start shopping around. The best deals are found online.

Monitor

There are three types of monitor namely CRT, LCD and LED. But CRT(cathode ray tube) monitors are disappearing in markets. LCD and LED are all same but only change in backlight. In LCD Florescent lamps are used, but in LED it is done by LED lamps. LED monitor is most preferable because it has more moving angle. 

 The next thing to select is aspect ratio. Monitors are available in 16:9  and 4:3 . The old monitors have aspect ratio 4:3.  But the HD videos are in 16:9 ratio. So 16:9 ratio is preferable.   

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RAM (Random-access memory)

Random-access memory

Random-access memory (RAM /ræm/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations.

Therefore, the time to access a given data location varies significantly depending on its physical location.
Today, random-access memory takes the form of integrated circuits. Strictly speaking, modern types of DRAM are not random access, as data is read in bursts, although the name DRAM / RAM has stuck.

 However, many types of SRAM, ROM, OTP, and NOR flash are still random access even in a strict sense. RAM is normally associated with volatile types of memory (such as DRAM memory modules), where its stored information is lost if the power is removed. Many other types of non-volatile memory are RAM as well, including most types of ROM and a type of flash memory called NOR-Flash. The first RAM modules to come into the market were created in 1951 and were sold until the late 1960s and early 1970s.

History

Early computers used relays, or delay lines for "main" memory functions. Ultrasonic delay lines could only reproduce data in the order it was written. Drum memory could be expanded at low cost but retrieval of non-sequential memory items required knowledge of the physical layout of the drum to optimize speed. Latches built out of vacuum tube triodes, and later, out of discrete transistors, were used for smaller and faster memories such as random-access register banks and registers. Such registers were relatively large, power-hungry and too costly to use for large amounts of data; generally only a few hundred or few thousand bits of such memory could be provided.

Magnetic core memory was the standard form of memory system until displaced by solid-state memory in integrated circuits, starting in the early 1970s. Robert H. Dennard invented dynamic random-access memory (DRAM) in 1968; this allowed replacement of a 4 or 6-transistor latch circuit by a single transistor for each memory bit, greatly increasing memory density at the cost of volatility. Data was stored in the tiny capacitance of each transistor, and had to be periodically refreshed in a few milliseconds before the charge could leak away.
Prior to the development of integrated read-only memory (ROM) circuits, permanent (or read-only) random-access memory was often constructed using diode matrices driven by address decoders, or specially wound core rope memory planes.

Types of RAM

The three main forms of modern RAM are static RAM (SRAM), dynamic RAM (DRAM) and phase-change memory (PRAM). In SRAM, a bit of data is stored using the state of a flip-flop. This form of RAM is more expensive to produce, but is generally faster and requires less power than DRAM and, in modern computers, is often used as cache memory for the CPU. DRAM stores a bit of data using a transistor and capacitor pair, which together comprise a memory cell. The capacitor holds a high or low charge (1 or 0, respectively), and the transistor acts as a switch that lets the control circuitry on the chip read the capacitor's state of charge or change it. As this form of memory is less expensive to produce than static RAM, it is the predominant form of computer memory used in modern computers.

Both static and dynamic RAM are considered volatile, as their state is lost or reset when power is removed from the system. By contrast, read-only memory (ROM) stores data by permanently enabling or disabling selected transistors, such that the memory cannot be altered. Writeable variants of ROM (such as EEPROM and flash memory) share properties of both ROM and RAM, enabling data to persist without power and to be updated without requiring special equipment. These persistent forms of semiconductor ROM include USB flash drives, memory cards for cameras and portable devices, etc. ECC memory (which can be either SRAM or DRAM) includes special circuitry to detect and/or correct random faults (memory errors) in the stored data, using parity bits or error correction code.

In general, the term RAM refers solely to solid-state memory devices (either DRAM or SRAM), and more specifically the main memory in most computers. In optical storage, the term DVD-RAM is somewhat of a misnomer since, unlike CD-RW or DVD-RW it does not need to be erased before reuse. Nevertheless a DVD-RAM behaves much like a hard disc drive if somewhat slower.

Memory hierarchy

Main article: Memory hierarchy

One can read and over-write data in RAM. Many computer systems have a memory hierarchy consisting of CPU registers, on-die SRAM caches, external caches, DRAM, paging systems and virtual memory or swap space on a hard drive. This entire pool of memory may be referred to as "RAM" by many developers, even though the various subsystems can have very different access times, violating the original concept behind the random access term in RAM. Even within a hierarchy level such as DRAM, the specific row, column, bank, rank, channel, or interleave organization of the components make the access time variable, although not to the extent that rotating storage media or a tape is variable. The overall goal of using a memory hierarchy is to obtain the higher possible average access performance while minimizing the total cost of the entire memory system (generally, the memory hierarchy follows the access time with the fast CPU registers at the top and the slow hard drive at the bottom).

In many modern personal computers, the RAM comes in an easily upgraded form of modules called memory modules or DRAM modules about the size of a few sticks of chewing gum. These can quickly be replaced should they become damaged or when changing needs demand more storage capacity. As suggested above, smaller amounts of RAM (mostly SRAM) are also integrated in the CPU and other ICs on the motherboard, as well as in hard-drives, CD-ROMs, and several other parts of the computer system.

Other uses of RAM

In addition to serving as temporary storage and working space for the operating system and applications, RAM is used in numerous other ways.

Virtual memory

Main article: virtual memory

Most modern operating systems employ a method of extending RAM capacity, known as "virtual memory". A portion of the computer's hard drive is set aside for a paging file or a scratch partition, and the combination of physical RAM and the paging file form the system's total memory. (For example, if a computer has 2 GB of RAM and a 1 GB page file, the operating system has 3 GB total memory available to it.) When the system runs low on physical memory, it can "swap" portions of RAM to the paging file to make room for new data, as well as to read previously swapped information back into RAM. Excessive use of this mechanism results in thrashing and generally hampers overall system performance, mainly because hard drives are far slower than RAM.

RAM disk

Software can "partition" a portion of a computer's RAM, allowing it to act as a much faster hard drive that is called a RAM disk. A RAM disk loses the stored data when the computer is shut down, unless memory is arranged to have a standby battery source.

Shadow RAM

Sometimes, the contents of a relatively slow ROM chip are copied to read/write memory to allow for shorter access times. The ROM chip is then disabled while the initialized memory locations are switched in on the same block of addresses (often write-protected). This process, sometimes called shadowing, is fairly common in both computers and embedded systems.

As a common example, the BIOS in typical personal computers often has an option called “use shadow BIOS” or similar. When enabled, functions relying on data from the BIOS’s ROM will instead use DRAM locations (most can also toggle shadowing of video card ROM or other ROM sections). Depending on the system, this may not result in increased performance, and may cause incompatibilities. For example, some hardware may be inaccessible to the operating system if shadow RAM is used. On some systems the benefit may be hypothetical because the BIOS is not used after booting in favor of direct hardware access. Free memory is reduced by the size of the shadowed ROMs.

Recent developments

Several new types of non-volatile RAM, which will preserve data while powered down, are under development. The technologies used include carbon nanotubes and approaches utilizing the magnetic tunnel effect. Amongst the 1st generation MRAM, a 128 KiB (128 × 2¹⁰ bytes) magnetic RAM (MRAM) chip was manufactured with 0.18 µm technology in the summer of 2003. In June 2004, Infineon Technologies unveiled a 16 MiB (16 × 2²⁰ bytes) prototype again based on 0.18 µm technology. There are two 2nd generation techniques currently in development: Thermal Assisted Switching (TAS) which is being developed by Crocus Technology, and Spin Torque Transfer (STT) on which Crocus, Hynix, IBM, and several other companies are working. Nantero built a functioning carbon nanotube memory prototype 10 GiB (10 × 2³⁰ bytes) array in 2004. Whether some of these technologies will be able to eventually take a significant market share from either DRAM, SRAM, or flash-memory technology, however, remains to be seen.

Since 2006, "solid-state drives" (based on flash memory) with capacities exceeding 256 gigabytes and performance far exceeding traditional disks have become available. This development has started to blur the definition between traditional random-access memory and "disks", dramatically reducing the difference in performance.

Some kinds of random-access memory, such as "EcoRAM", are specifically designed for server farms, where low power consumption is more important than speed.

Memory wall

The "memory wall" is the growing disparity of speed between CPU and memory outside the CPU chip. An important reason for this disparity is the limited communication bandwidth beyond chip boundaries. From 1986 to 2000, CPU speed improved at an annual rate of 55% while memory speed only improved at 10%. Given these trends, it was expected that memory latency would become an overwhelming bottleneck in computer performance.
CPU speed improvements slowed significantly partly due to major physical barriers and partly because current CPU designs have already hit the memory wall in some sense. Intel summarized these causes in a 2005 document.

“First of all, as chip geometries shrink and clock frequencies rise, the transistor leakage current increases, leading to excess power consumption and heat... Secondly, the advantages of higher clock speeds are in part negated by memory latency, since memory access times have not been able to keep pace with increasing clock frequencies. Third, for certain applications, traditional serial architectures are becoming less efficient as processors get faster (due to the so-called Von Neumann bottleneck), further undercutting any gains that frequency increases might otherwise buy. In addition, partly due to limitations in the means of producing inductance within solid state devices, resistance-capacitance (RC) delays in signal transmission are growing as feature sizes shrink, imposing an additional bottleneck that frequency increases don't address.”

The RC delays in signal transmission were also noted in Clock Rate versus IPC: The End of the Road for Conventional Microarchitectures which projects a maximum of 12.5% average annual CPU performance improvement between 2000 and 2014. The data on Intel Processors clearly shows a slowdown in performance improvements in recent processors. However, Intel's Core 2 Duo processors (codenamed Conroe) showed a significant improvement over previous Pentium 4 processors; due to a more efficient architecture, performance increased while clock rate actually decreased.

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Download Font with Indian Rupee Symbol

Font with Indian Rupee Symbol

We have made the first font with support for Indian currency symbol.

    

DOWNLOAD font

 How to use ?

1. Download the above attached font link.
2. Install the font. (by double click on the downloaded).
                or
  (It is easy. Just copy the font and paste it in "Fonts" folder in control panel)
3. Start using it. :)

Note;-
      Select Rupee Font in MS office to use.

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Windows 8

Windows 8 is a version of Microsoft Windows (an operating system developed by Microsoft) for use on personal computers, including home and business desktops, laptops, tablets, and home theater PCs. Development of Windows 8 started before the release of its predecessor, Windows 7, in 2009. It was announced at CES 2011, and followed by the release of three pre-release versions from September 2011 to May 2012. The operating system was released to manufacturing on August 1, 2012, and was released for general availability on October 26, 2012.
Windows 8 introduces significant changes to the operating system's platform, primarily focused towards improving its user experience on mobile devices such as tablets to better compete with other mobile operating systems like Android and Apple's iOS. Windows 8 features a new touch user interface and shell based on Microsoft's "Metro" design language, featuring a new Start screen with a grid of dynamically updating tiles that represent applications. The Start screen replaces the "Start menu" of earlier Windows versions. There is a new app platform with an emphasis on touchscreen input, and the new Windows Store to obtain and/or purchase applications to run on the operating system.
In addition, Windows 8 takes advantage of new or emerging technologies like USB 3.0, 4Kn Advanced Format, near field communications, cloud computing, and the low-power ARM architecture. It includes new security features such as built-in antivirus capabilities, a new installation process optimized for digital distribution, and support for secure boot (a UEFI feature which allows operating systems to be digitally signed to prevent malware from altering the boot process). Synchronization of certain apps and settings between multiple devices is supported.
Windows 8 was released to mixed reception. Although reaction towards its performance improvements, security enhancements, and improved support for touchscreen devices was positive, the new user interface of the operating system has been widely criticized for being potentially confusing and difficult to learn (especially when used with a keyboard and mouse instead of a touchscreen). Despite these shortcomings, 60 million Windows 8 licenses have been sold through January 2013. This includes upgrades and sales to OEMs for new PCs.
Windows 8.1 is scheduled for release in late 2013 and, according to Microsoft, will change "key aspects" of how Windows 8 is used,  including the reinstatement of the Start button.

Developer
Microsoft Corporation
Website	windows.microsoft.com
Releases
Initial release	August 1, 2012; 11 months ago
General availability	October 26, 2012; 8 months ago
Latest stable release	6.2 (Build 9200) (August 1, 2012; 11 months ago)
Latest preview release	6.3 (Build 9431)
License	Proprietary commercial software
Kernel type	Hybrid
Update method	Windows Update
Platform support	IA-32, x64, and ARM
Preceded by	Windows 7 (2009)
Support status
Start date: October 30, 2012 Mainstream support: Until January 9, 2018 Extended support: Until January 10, 2023

Development history

Windows 8 development started before Windows 7 had shipped in 2009. At the Consumer Electronics Show in January 2011, Microsoft announced that the next version of Windows would add support for devices with ARM microprocessors, and showcased an early version of what would become Windows 8, NT 6.2 build 7867, running on several prototype ARM devices. Details also began to surface about a new application framework for Windows 8 codenamed "Jupiter", which would be used to make "immersive" applications using XAML (similarly to Windows Phone and Silverlight) that could be distributed via a new packaging system and a rumored app store.
Three milestone releases of Windows 8 leaked to the general public. Milestone 1, Build 7850, was leaked on April 12, 2011. It was the first build where the text of a window was written centered instead of aligned to the left. It was also probably the first appearance of the Metro-style font, and its wallpaper had the text shhh... let's not leak our hard work. However, its detailed build number reveals that the build was created on September 22, 2010. The leaked copy edition was Enterprise edition. The OS still reads as "Windows 7". Milestone 2, Build 7955, was leaked on April 25, 2011. The traditional Blue Screen of Death (BSoD) was replaced by a new Black screen, although this was later scrapped. This build introduced a new ribbon in Windows Explorer. Build 7959, with minor changes but the first 64-bit version, was leaked on May 1, 2011. The "Windows 7" logo was temporarily replaced with text displaying "Microsoft Confidential". On June 17, 2011, build 7989 64-bit edition was leaked. It introduced a new boot screen featuring the same fish as the default Windows 7 Beta wallpaper, which was later scrapped, and the circling dots as featured in the final (although the final version comes with smaller circling dots throbber). It also had the text Welcome below them, although this was also scrapped.
On June 1, 2011, Microsoft unveiled Windows 8's new user interface as well as additional features at both Computex Taipei and the D9: All Things Digital conference in California.
The "Building Windows 8" blog launched on August 15, 2011, featuring details surrounding Windows 8's features and its development process.

Windows Store apps

Windows 8 introduces a new style of application, Windows Store apps. According to Microsoft developer Jensen Harris, these apps are to be optimized for touchscreen environments and will be more specialized than current desktop applications. Apps can run either in a full-screen mode, or be snapped to the side of a screen. Apps can provide toast notifications on screen or animate their tiles on the Start screen with dynamic content. Apps can use "contracts"; a collection of hooks to provide common functionality that can integrate with other apps, such as search and sharing. Apps can also provide integration with other services; for example, the People app can connect to a variety of different social networks and services (such as Facebook, Skype, and People service), while the Photos app can aggregate photos from services such as Facebook and Flickr.
Windows Store apps run within a new set of APIs known as the Windows Runtime, which supports programming languages such as C, C++, VB.NET, C#, along with HTML5 and JavaScript. Depending on the language used, apps written for Windows Runtime can be compatible with both Intel and ARM versions of Windows. Components may be compiled as Windows Runtime Components, permitting consumption by all of the Windows Runtime supported languages. To ensure stability and security, apps run within a sandboxed environment, and require permissions to access certain functionality, such as accessing the Internet or a camera.
Retail versions of Windows 8 will be able to install these apps only through the Windows Store—a namesake distribution platform which offers both apps, and listings for desktop programs certified for comparability with Windows 8. A method to sideload apps from outside the Windows Store is available to devices running Windows 8 Enerprise and joined to a domain; Windows 8 Pro and Windows RT devices that are not part of a domain can also sideload apps, but only after special product keys are obtained through volume licensing.
The term "Immersive app" had been used internally by Microsoft developers to refer to the apps prior to the first official presentation of Windows 8, after which they were referred to as "Metro-style apps" in reference to the Metro design language. The term was phased out in August 2012; a Microsoft spokesperson denied rumors that the change was related to a potential trademark issue, and stated that "Metro" was only a codename that would be replaced prior to Windows 8's release. Following these reports, the terms "Modern UI-style apps", "Windows 8-style apps" and "Windows Store apps" began to be used by various Microsoft documents and material to refer to the new apps. In an interview on September 12, 2012, Soma Somasegar (vice president of Microsoft's development software division) confirmed that "Windows Store apps" would be the official term for the apps.

Web browsers

Exceptions to the restrictions faced by Windows Store apps are given to web browsers; the user's default browser can provide a "New experience enabled" (formerly "Metro-style enabled") version that runs within the "Metro" shell like other apps. Web browser apps are distributed alongside desktop web browsers, and also have access to functionality unavailable to other apps, such as being able to permanently run in the background, use multiple background processes, and use Windows API code instead of WinRT (allowing for code to be re-used with the desktop version, while still taking advantage of WinRT features such as contracts to integrate with charms).
The developers of both Chrome and Firefox committed to developing versions of their browsers to run in this environment; while Chrome's "Windows 8 mode" uses the existing desktop interface, Firefox's Metro version (which is currently available in development builds) uses a touch-optimized interface inspired by the Android version of Firefox.

Interface and desktop

Windows 8 introduces significant changes to the operating system's user interface, many of which are aimed at improving its experience on tablet computers and other touchscreen devices. The new user interface is based on Microsoft's Metro design language, and uses a Start screen similar to that of Windows Phone as the primary means of launching applications. The Start screen displays a customizable array of tiles linking to various apps and desktop programs, some of which can display constantly updated information and content through "live tiles". As a form of multi-tasking, apps can be snapped to the side of a screen. Alongside the traditional Control Panel, a new simplified and touch-optimized settings app known as "PC Settings" is used for basic configuration and user settings. It does not include many of the advanced options still accessible from the normal Control Panel.
A vertical toolbar known as the charms (accessed by swiping from the right edge of a touchscreen, or pointing the cursor at hotspots in the right corners of a screen) provides access to system and app-related functions, such as search, sharing, device management, settings, and a Start button. The traditional desktop environment for running desktop applications is accessed via a tile on the Start screen. The Start button on the taskbar has been removed in favor of the Start charm and a hotspot in the lower-left corner of the screen, which displays a large tooltip displaying a thumbnail of the Start screen. Swiping from the left edge of a touchscreen or clicking in the top-left corner of the screen allows one to switch between apps and the Desktop. Pointing the cursor in the top-left corner of the screen and moving down reveals a thumbnail list of active apps. Aside from the removal of the Start button, the desktop on Windows 8 is similar to that of Windows 7, except that the Aero Glass theme has been replaced by a flatter, solid-colored design inspired by the Metro interface.

Secure boot

See also: Unified Extensible Firmware Interface#Secure boot and Hardware restrictions#Windows 8

Windows 8 supports a feature of the UEFI specification known as "Secure boot", which uses a public-key infrastructure to verify the integrity of the operating system and prevent unauthorized programs such as bootkits from infecting the device.
Microsoft faced criticism (particularly from free software supporters) for mandating that devices receiving its optional certification for Windows 8 have secure boot enabled by default using a key provided by Microsoft. Concerns were raised that secure boot could prevent or hinder the use of alternate operating systems such as Linux. In response to the criticism, Microsoft developer Tony Mangefeste stated that "At the end of the day, the customer is in control of their PC. Microsoft's philosophy is to provide customers with the best experience first, and allow them to make decisions themselves."
Microsoft's certification requirements eventually revealed that UEFI firmware on x86 systems must allow users to re-configure or turn off secure boot, but that this must not be possible on ARM-based systems (Windows RT). Microsoft faced further criticism for its decision to restrict Windows RT devices by using this functionality. Tom Warren, in an article on The Verge, said that other smartphones and tablets are typically sold in a locked-down state. No mandate is made regarding the installation of third-party certificates that would enable running alternative software.

Removed features

Main article: List of features removed in Windows 8

Several notable features have been removed in Windows 8, beginning with the traditional Start menu. Support for playing DVDs has been removed from Windows Media Player due to the cost of licensing the necessary decoders (especially for devices which do not include optical disc drives at all) and the prevalence of streaming services such as Netflix. For the same reasons, Windows Media Center will no longer be included by default on Windows 8, but the software (which also includes support for DVD playback) can be purchased in the "Pro Pack" (for the base version of Windows 8, which also upgrades the system to Windows 8 Pro) or "Media Center Pack" (for Windows 8 Pro) add-ons. Windows 8 will still support third-party DVD playback software.
Backup and Restore, the former backup app of Windows, is deprecated. It still ships with Windows 8 and continues to work on preset schedules, but is pushed to the background and can only be accessed through a Control Panel applet called "Windows 7 File Recovery". Shadow Copy, a component of Windows Explorer that once saved previous versions of changed files, no longer protects local files and folders. It can only access previous versions of shared files stored on a Windows Server computer. The subsystem on which these components worked, however, is still available for other software to use.

Hardware requirements

PCs

The minimum system requirements for Windows 8 are slightly higher than those of Windows 7. The CPU must support the Physical Address Extension (PAE), NX bit, and SSE2. Windows Store apps require a screen resolution of 1024×768 or higher to run. They require a screen resolution of 1366×768 or higher for snap functionality. To receive certification, Microsoft requires candidate x86 systems to resume from standby in 2 seconds or less.

Minimum hardware requirements for Windows 8

Tablets and convertibles

Microsoft released minimum hardware requirements for new tablet and convertible devices certified for Windows 8, and defined a convertible form factor as a standalone device that combines the PC, display and rechargeable power source with a mechanically attached keyboard and pointing device in a single chassis. A convertible can be transformed into a tablet where the attached input devices are hidden or removed leaving the display as the only input mechanism. On March 12, 2013, Microsoft amended its certification requirements to only require that screens on tablets have a minimum resolution of 1024×768 (down from the previous 1366×768). The amended requirement is intended to allow "greater design flexibility" for future products.Tablets and convertibles

Hardware certification requirements for Windows tablets

Software compatibility

The three desktop editions of Windows 8 are sold in two sub-editions: 32-bit and 64-bit. The 32-bit sub-edition runs on CPUs compatible with x86 architecture 3rd generation (known as IA-32) or newer, and can run 32-bit and 16-bit applications, although 16-bit support must be enabled first. (16-bit applications are developed for CPUs compatible with x86 2nd generation, first conceived in 1978. Microsoft started moving away from this architecture since Windows 95.)
The 64-bit sub-edition runs on CPUs compatible with x86 8th generation (known as x86-64, or x64) or newer, and can run 32-bit and 64-bit programs. 32-bit programs and operating system are restricted to supporting only 4 gigabytes of memory while 64-bit systems can theoretically support 2048 gigabytes of memory. 64-bit operating systems require a different set of device drivers than those of 32-bit operating systems.

Windows RT, the only edition of Windows 8 for systems with ARM processors, only supports applications included with the system (such as a special version of Office 2013), supplied through Windows Update, or Windows Store apps, to ensure that the system only runs applications that are optimized for the architecture. Windows RT does not support running IA-32 or x64 applications. Windows Store apps can either support both the x86 and ARM architectures, or compiled to support a specific architecture.

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Speaker

A loudspeaker (or "speaker") is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful. The most common form of loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a permanent magnet, but many other types exist. Where high fidelity reproduction of sound is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range. Miniature loudspeakers are found in devices such as radio and TV receivers, and many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts.

      The term "loudspeaker" may refer to individual transducers (known as "drivers") or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a wide range of frequencies, most loudspeaker systems employ more than one driver, particularly for higher sound pressure level or maximum accuracy. Individual drivers are used to reproduce different frequency ranges. The drivers are named subwoofers (for very low frequencies); woofers (low frequencies); mid-range speakers (middle frequencies); tweeters (high frequencies); and sometimes supertweeters, optimized for the highest audible frequencies. The terms for different speaker drivers differ, depending on the application. In two-way systems there is no mid-range driver, so the task of reproducing the mid-range sounds falls upon the woofer and tweeter. Home stereos use the designation "tweeter" for the high frequency driver, while professional concert systems may designate them as "HF" or "highs". When multiple drivers are used in a system, a "filter network", called a crossover, separates the incoming signal into different frequency ranges and routes them to the appropriate driver. A loudspeaker system with n separate frequency bands is described as "n-way speakers": a two-way system will have a woofer and a tweeter; a three-way system employs a woofer, a mid-range, and a tweeter. Loudspeakers were described as "dynamic" to distinguish them from the earlier moving iron speaker, or speakers using piezoelectric or electrostatic systems as opposed to a voice coil that moves through a steady magnetic field.

Driver design

The most common type of driver, commonly called a dynamic loudspeaker, uses a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension, commonly called a spider, that constrains a voice coil to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver's magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical signal coming from the amplifier. The following is a description of the individual components of this type of loudspeaker.
The diaphragm is usually manufactured with a cone- or dome-shaped profile. A variety of different materials may be used, but the most common are paper, plastic, and metal. The ideal material would be 1) rigid, to prevent uncontrolled cone motions; 2) have low mass, to minimize starting force requirements and energy storage issues; 3) be well damped, to reduce vibrations continuing after the signal has stopped with little or no audible ringing due to its resonance frequency as determined by its usage. In practice, all three of these criteria cannot be met simultaneously using existing materials; thus, driver design involves trade-offs. For example, paper is light and typically well damped, but is not stiff; metal may be stiff and light, but it usually has poor damping; plastic can be light, but typically, the stiffer it is made, the poorer the damping. As a result, many cones are made of some sort of composite material. For example, a cone might be made of cellulose paper, into which some carbon fiber, Kevlar, glass, hemp or bamboo fibers have been added; or it might use a honeycomb sandwich construction; or a coating might be applied to it so as to provide additional stiffening or damping.
The chassis, frame, or basket, is designed to be rigid, avoiding deformation that could change critical alignments with the magnet gap, perhaps causing the voice coil to rub against the sides of the gap. Chassis are typically cast from aluminum alloy, or stamped from thin steel sheet, although molded plastic and damped plastic compound baskets are becoming common, especially for inexpensive, low-mass drivers. Metallic chassis can play an important role in conducting heat away from the voice coil; heating during operation changes resistance, causing physical dimensional changes, and if extreme, may even demagnetize permanent magnets.
The suspension system keeps the coil centered in the gap and provides a restoring (centering) force that returns the cone to a neutral position after moving. A typical suspension system consists of two parts: the spider, which connects the diaphragm or voice coil to the frame and provides the majority of the restoring force, and the surround, which helps center the coil/cone assembly and allows free pistonic motion aligned with the magnetic gap. The spider is usually made of a corrugated fabric disk, impregnated with a stiffening resin. The name comes from the shape of early suspensions, which were two concentric rings of Bakelite material, joined by six or eight curved "legs." Variations of this topology included the addition of a felt disc to provide a barrier to particles that might otherwise cause the voice coil to rub. The German firm Rulik still offers drivers with uncommon spiders made of wood.
The cone surround can be rubber or polyester foam, or a ring of corrugated, resin coated fabric; it is attached to both the outer diaphragm circumference and to the frame. These different surround materials, their shape and treatment can dramatically affect the acoustic output of a driver; each class and implementation having advantages and disadvantages. Polyester foam, for example, is lightweight and economical, but is degraded by exposure to ozone, UV light, humidity and elevated temperatures, limiting its useful life to about 15 years.
The wire in a voice coil is usually made of copper, though aluminum—and, rarely, silver—may be used. The advantage of aluminum is its light weight, which raises the resonant frequency of the voice coil and allows it to respond more easily to higher frequencies. A disadvantage of aluminum is that it is not easily soldered, and so connections are instead often crimped together and sealed. These connections can corrode and fail in time. Voice-coil wire cross sections can be circular, rectangular, or hexagonal, giving varying amounts of wire volume coverage in the magnetic gap space. The coil is oriented co-axially inside the gap; it moves back and forth within a small circular volume (a hole, slot, or groove) in the magnetic structure. The gap establishes a concentrated magnetic field between the two poles of a permanent magnet; the outside of the gap being one pole, and the center post (called the pole piece) being the other. The pole piece and backplate are often a single piece, called the poleplate or yoke.
Modern driver magnets are almost always permanent and made of ceramic, ferrite, Alnico, or, more recently, rare earth such as neodymium and Samarium cobalt. A trend in design—due to increases in transportation costs and a desire for smaller, lighter devices (as in many home theater multi-speaker installations)—is the use of the last instead of heavier ferrite types. Very few manufacturers still produce electrodynamic loudspeakers with electrically powered field coils, as was common in the earliest designs (one such is French). When high field-strength permanent magnets became available, Alnico, an alloy of aluminum, nickel, and cobalt became popular, since it dispensed with the power supply problems of field-coil drivers. Alnico was used for almost exclusively until about 1980. Alnico magnets can be partially degaussed (i.e., demagnetized) by accidental 'pops' or 'clicks' caused by loose connections, especially if used with a high power amplifier. This damage can be reversed by "recharging" the magnet.

Wiring connections

Most loudspeakers use two wiring points to connect to the source of the signal (for example, to the audio amplifier or receiver). This is usually done using binding posts or spring clips on the back of the enclosure. If the wires for the left and right speakers (in a stereo setup) are not connected "in phase" with each other (the + and − connections on the speaker and amplifier should be connected + to + and − to −), the loudspeakers are out of phase. Given identical signals, motion in one cone is in the opposite direction of the other. This typically causes monophonic material in a stereo recording to be canceled out, reduced in level, and made more difficult to localize, all due to destructive interference of the sound waves. The cancellation effect is most noticeable at frequencies where the speakers are separated by a quarter wavelength or less; low frequencies are affected the most. This type of wiring error does not damage speakers, but is not optimal.

 Speaker specifications generally include:

• Speaker or driver type (individual units only) – Full-range, woofer, tweeter, or mid-range.
• Size of individual drivers. For cone drivers, the quoted size is generally the outside diameter of the basket. However, it may less commonly also be the diameter of the cone surround, measured apex to apex, or the distance from the center of one mounting hole to its opposite. Voice-coil diameter may also be specified. If the loudspeaker has a compression horn driver, the diameter of the horn throat may be given.
• Rated Power – Nominal (or even continuous) power, and peak (or maximum short-term) power a loudspeaker can handle (i.e., maximum input power before destroying the loudspeaker; it is never the sound output the loudspeaker produces). A driver may be damaged at much less than its rated power if driven past its mechanical limits at lower frequencies.Tweeters can also be damaged by amplifier clipping (amplifier circuits produce large amounts of energy at high frequencies in such cases) or by music or sine wave input at high frequencies. Each of these situations might pass more energy to a tweeter than it can survive without damage. In some jurisdictions, power handling has a legal meaning allowing comparisons between loudspeakers under consideration. Elsewhere, the variety of meanings for power handling capacity can be quite confusing.
• Impedance – typically 4 Ω (ohms), 8 Ω, etc.
• Baffle or enclosure type (enclosed systems only) – Sealed, bass reflex, etc.
• Number of drivers (complete speaker systems only) – two-way, three-way, etc.

and optionally:

• Crossover frequency(ies) (multi-driver systems only) – The nominal frequency boundaries of the division between drivers.
• Frequency response – The measured, or specified, output over a specified range of frequencies for a constant input level varied across those frequencies. It sometimes includes a variance limit, such as within "± 2.5 dB."
• Thiele/Small parameters (individual drivers only) – these include the driver's F_s (resonance frequency), Q_ts (a driver's Q; more or less, its damping factor at resonant frequency), V_as (the equivalent air compliance volume of the driver), etc.
• Sensitivity – The sound pressure level produced by a loudspeaker in a non-reverberant environment, often specified in dB and measured at 1 meter with an input of 1 watt (2.83 rms volts into 8 Ω), typically at one or more specified frequencies. Manufacturers often use this rating in marketing material.
• Maximum sound pressure level – The highest output the loudspeaker can manage, short of damage or not exceeding a particular distortion level. Manufacturers often use this rating in marketing material—commonly without reference to frequency range or distortion level.

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Universal Serial Bus

Universal Serial Bus (USB) is an industry standard developed in the mid-1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices.
USB was designed to standardize the connection of computer peripherals (including keyboards, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters) to personal computers, both to communicate and to supply electric power. It has become commonplace on other devices, such as smartphones, PDAs and video game consoles. USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices.
As of 2008, approximately six billion USB ports and interfaces were in the global marketplace, and about 2 billion were being sold each year.

History

A group of seven companies began the development of USB in 1994: Compaq, DEC, IBM, Intel, Microsoft, NEC and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data rates for external devices. A team including Ajay Bhatt worked on the standard at Intel; the first integrated circuits supporting USB were produced by Intel in 1995.
The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/s "Low Speed" and 12 Mbit/s "Full Speed". The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks.

A USB Standard Type A plug, the most common USB plug

The USB 2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum (USB-IF) at the end of 2001. Hewlett-Packard(hp), Intel, Lucent Technologies (now Alcatel-Lucent), NEC and Philips jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 480 Mbit/s, a forty times increase over the original USB 1.1 specification.
The USB 3.0 specification was published on 12 November 2008. Its main goals were to increase the data transfer rate (up to 5 Gbit/s), decrease power consumption, increase power output, and be backwards-compatible with USB 2.0.USB 3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB 2.0 bus. For this reason, the new version is also called SuperSpeed. The first USB 3.0 equipped devices were presented in January 2010.

Version history

A PCI USB 2.0 card for a computer motherboard

Prereleases

The USB standard evolved through several versions before its official release in 1996:

• USB 0.7: Released in November 1994.
• USB 0.8: Released in December 1994.
• USB 0.9: Released in April 1995.
• USB 0.99: Released in August 1995.
• USB 1.0 Release Candidate: Released in November 1995.

USB 1 (Full Speed)

Released in January 1996, USB 1 specified data rates of 1.5 Mb/s (Low-Bandwidth) and 12 Mb/s (Full-Bandwidth). It did not allow for extension cables or pass-through monitors (due to timing and power limitations). Few USB devices made it to market until USB 1.1, released in August 1998, which fixed problems identified in 1.0, mostly relating to hubs. 1.1 was the earliest revision that was widely adopted. USB 1 is usually colored white, but some white USB ports are "USB 2 Compatible"

USB 2.0 (High Speed)

The Hi-Speed USB Logo

• USB 2.0: Released in April 2000. Added higher maximum signaling rate of 480 Mbit/s (effective throughput up to 35 MB/s or 280 Mbit/s) (now called "Hi-Speed"). Further modifications to the USB specification have been done via Engineering Change Notices (ECN). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org

USB 3.0 (Super Speed)

Main article: USB 3.0

The Super-Speed USB Logo

USB 3.0 was released in November 2008. The standard defines a new "SuperSpeed" mode with a signalling speed of 5 Gbit/s and a usable data rate of up to 4 Gbit/s. USB 3.0 reduces the time required for data transmission, thereby reducing power consumption, and is backwards compatible with USB 2.0. The USB 3.0 Promoter Group announced on 17 November 2008 that the specification of version 3.0 had been completed and had made the transition to the USB Implementers Forum (USB-IF), the managing body of USB specifications.This move effectively opened the specification to hardware developers for implementation in products. The new "SuperSpeed" bus provides a fourth transfer mode at 5.0 Gbit/s (raw data rate), in addition to the modes supported by earlier versions. The payload throughput is 4 Gbit/s (using 8b/10b encoding), and the specification considers it reasonable to achieve around 3.2 Gbit/s (0.4 GB/s or 400 MB/s), which should increase with future hardware advances. Communication is full-duplex during SuperSpeed; in the modes supported previously, by 1.x and 2.0, communication is half-duplex, with direction controlled by the host.

• Power Handling Capabilities: As with previous USB versions, USB 3.0 ports come in low-power and high-power variants, providing 150 mA and 900 mA respectively while simultaneously transmitting data at SuperSpeed rates. Additionally, there is a Battery Charging Specification (Version 1.2 – December 2010), which increases the power handling capability to 1.5 A but does not allow concurrent data transmission.The Battery Charging Specification requires that the physical ports themselves be capable of handling 5 A of current but the specification limits the maximum current drawn to 1.5 A.

A January 2013 press release from the USB group reveals plans to update USB 3 to 10 Gbit/s to put it on par with Thunderbolt by mid-2013.

System design

The design architecture of USB is asymmetrical in its topology, consisting of a host, a multitude of downstream USB ports, and multiple peripheral devices connected in a tiered-star topology. Additional USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels. A USB host may implement multiple host controllers and each host controller may provide one or more USB ports. Up to 127 devices, including hub devices if present, may be connected to a single host controller. USB devices are linked in series through hubs. One hub—built into the host controller—is the root hub.

Device classes

The functionality of USB devices is defined by class codes, communicated to the USB host to affect the loading of suitable software driver modules for each connected device. This provides for adaptability and device independence of the host to support new devices from different manufacturers.
Device classes include:

Class	Usage	Description	Examples, or exception
00h	Device	Unspecified	Device class is unspecified, interface descriptors are used to determine needed drivers
01h	Interface	Audio	Speaker, microphone, sound card, MIDI
02h	Both	Communications and CDC Control	Modem, Ethernet adapter, Wi-Fi adapter
03h	Interface	Human interface device (HID)	Keyboard, mouse, joystick
05h	Interface	Physical Interface Device (PID)	Force feedback joystick
06h	Interface	Image	Webcam, scanner
07h	Interface	Printer	Laser printer, inkjet printer, CNC machine
08h	Interface	Mass storage (MSC or UMS)	USB flash drive, memory card reader, digital audio player, digital camera, external drive
09h	Device	USB hub	Full bandwidth hub
0Ah	Interface	CDC-Data	Used together with class 02h: communications and CDC control
0Bh	Interface	Smart Card	USB smart card reader
0Dh	Interface	Content security	Fingerprint reader
0Eh	Interface	Video	Webcam
0Fh	Interface	Personal Healthcare	Pulse monitor (watch)
10h	Interface	Audio/Video (AV)	Webcam, TV
DCh	Both	Diagnostic Device	USB compliance testing device
E0h	Interface	Wireless Controller	Bluetooth adapter, Microsoft RNDIS
EFh	Both	Miscellaneous	ActiveSync device
FEh	Interface	Application-specific	IrDA Bridge, Test & Measurement Class (USBTMC), USB DFU (Direct Firmware update)
FFh	Both	Vendor-specific	Indicates that a device needs vendor specific drivers

USB mass storage / USB key

A flash drive, a typical USB mass-storage device

USB implements connections to storage devices using a set of standards called the USB mass storage device class (MSC or UMS). This was at first intended for traditional magnetic and optical drives, but has been extended to support a wide variety of devices, particularly flash drives, because many systems can be controlled with the familiar metaphor of file manipulation within directories. The process of making a novel device look like a familiar device is also known as extension. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.
    Though most post-Summer 2004 computers are capable of booting from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage: buses such as Parallel ATA (PATA or IDE), Serial ATA (SATA), or SCSI fulfill that role in PC class computers. However, USB has one important advantage in that it is possible to install and remove devices without rebooting the computer (hot-swapping), making it useful for mobile peripherals, including drives of various kinds. Originally conceived and still used today for optical storage devices (CD-RW drives, DVD drives and so on), several manufacturers offer external portable USB hard disk drives, or empty enclosures for disk drives, which offer performance comparable to internal drives, limited by the current number and type of attached USB devices and by the upper limit of the USB interface (in practice about 30 MB/s for USB 2.0 and potentially 400 MB/s or more^[ for USB 3.0). These external drives have typically included a "translating device" that bridges between a drive's interface to a USB interface port. Functionally, the drive appears to the user much like an internal drive. Other competing standards for external drive connectivity include eSATA, ExpressCard (now at version 2.0), FireWire (IEEE 1394), and most recently Thunderbolt.
Another use for USB mass storage devices is the portable execution of software applications (such as web browsers and VoIP clients) with no need to install them on the host computer.

Media Transfer Protocol

Media Transfer Protocol (MTP) was designed by Microsoft to give higher-level access to a device's filesystem than USB mass storage, at the level of files rather than disk blocks. It also has optional DRM features. MTP was designed for use with portable media players, but it has since been adopted as the primary storage access protocol of the Android operating system.

Human interface devices

Main article: USB human interface device class

Joysticks, keypads, tablets and other human-interface devices (HIDs) are also progressively migrating from MIDI, and PC game port connectors to USB.
USB mice and keyboards can usually be used with older computers that have PS/2 connectors with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, an adaptor that contain no logic circuitry may be used: the hardware in the USB keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port. These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.

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