Computer Keyboard Parts & Functions

QWERTY Pad

• The QWERTY pad is the main section of letters on the keyboard. You use these letters mainly for typing and, in various combinations, as action shortcuts in programs and computer games.

Number Pads

• The far right side of the keyboard features a number pad that resembles a calculator. This pad is essential for numbers-oriented programs such as Excel, but you also can use it to input numbers while typing. More number keys are just above the QWERTY pad; these keys also feature symbols activated by the “Shift” key.

  Arrow Keys

  • The right bottom of a keyboard features four directional arrow keys. These keys provide navigation through documents and help you scroll in Web browsers.

  F Bar

  • The top of a keyboard features the F Keys, a selection of keys that extends to F12 on most keyboards. These keys serve different functions. For example, pressing “Alt" and "F4” exits out of a program. Pressing “F1” usually opens a help screen.

  Extra Keys

  • Newer keyboards sometimes have shortcut keys above the F Keys. These might include “Power,” “Sleep Mode,” “Calculator,” “My Computer” and “Web.” Some also include media controls for movies and music.

Types of Keyboards

Standard Keyboard

Though standard keyboards have undergone considerable changes in design over the last 20 years, their basic layout remains similar.

The average number of keys on a regular keyboard is 105, though some older versions have keys in the range of 95-103.

Even though standard keyboards are the most basic form of keyboards, they can have slight variations, especially in the manner the keys are placed.

QWERTY keyboards are the most common and have the six alphabets Q, W, E, R, T, and Y in the first row, while in AZERTY keyboards these letters are replaced with A, Z, E, R, T, and Y in the first row.

AZERTY keyboards are used primarily in French countries. Other forms include QWERTZ and Dvorak keyboards.

Ergonomic Keyboards

Ergonomic keyboards are designed in such a way that typing can be done putting the least amount of stress on the fingers and wrist.

This is a radical type of keyboard designed to prevent Carpal Tunnel Syndrome, which causes numbness and tingling sensation in the hands and fingers after typing for a long duration.

Ergonomic keyboards come in two forms:

As a single piece, where a group of keys have been split in such a way, that the angle at which the user places his or her wrist to type is the least stressful.
In the form of separate pieces, each having a group of keys, so that the user can set the angle according to his or her convenience.

Hence, these keyboards differ from the usual single piece keyboards that are straight and contain keys as one whole group.

Wireless Keyboards

As the name suggests, these keyboards do not need to be connected to the computer via a wire.

This makes it very convenient for the user to use the keyboard comfortably.

Wireless keyboards use three basic types of connections, Bluetooth, Infrared (IR), and Radio Frequency to connect to the computer.

All the three types of wireless keyboards need external power to function. In most models, the power comes from either 2 or 3 'AA' or 'AAA' batteries.

Rare models might have an included battery, which can be charged with the help of a USB cable.

In addition to this, all three types also use a transceiver, which connects to a port on the computer and maintains contact between the computer and the keyboard.

The best of the lot are Bluetooth keyboards.

These keyboards connect using Bluetooth technology, and hence have the best range of about 30 feet. Moreover, they are also compatible with other devices that support Bluetooth technology.

Next in line are RF keyboards, which have a limited range of only about 6 feet, but are much cheaper than Bluetooth keyboards, and much more effective than IR keyboards.

The latest models of RF keyboards have no issues like frequency disturbance, and can be the best bet if you do not need more than around 5 feet of freedom.


Compact Keyboards

Compact keyboards are slim and usually do not have the numeric keypad that is present on the right side of other keyboards.

These are typically used in laptops, where sizing issues make it difficult to accommodate a standard keyboard.

These are not extremely small in size, but offer portability during travel and storage.

Internet Keyboards

The Internet is one of the main reasons why a majority of the people use computers these days.

Internet keyboards have special keys, called hot keys, which perform functions related to Internet usage.

Typical hot keys have functions like back, forward, bookmarks list, e-mail inbox, Google search, YouTube, shopping online, etc.

This makes browsing the Internet very convenient, as the user does not have to go through the process of clicking buttons via a mouse.

These days, many standard keyboards have adopted the concept of Internet keyboards by placing these buttons on the top, since almost every kind of work requires the use of the Internet.

Gaming Keyboards

As the name suggests, gaming keyboards are designed specifically for gamers. They include features meant to enhance gaming experience, as well as provide convenient usage for gamers.

They include features like volume control, key lighting, programmable keys, interchangeable keys, touch screens to customize the keyboard, in-built joysticks, fancy lighting, etc.

Parts of Graphics Card

Parts of Graphics Card

Main Graphics Card Manufacturers

There are 2 main rivals

1.     NVidia

2.     ATI

Both brands are working hard to compete each other in the race of graphics technology.

Nvidia has introduced:

1.     GeForce

2.     Quadro

3.     nForce

4.     Tegra

GeForce technology is introduced to make our personal user computer capable of playing graphical enhanced games like doom, FarCry etc.

Quadro technology is introduced to make workstations capable to run CAD (Computer Aided Designs) and also DCC (Digital Content Creation)

nForce technology is introduced to make motherboards capable of playing games. Chip-set of nForce is placed on motherboard to facilitate general user with economic pack.

Tegra technology is introduced for mobile graphics.

Similarly ATI has divisions of technology. Like

1.     Mach Series

2.     Rage Series

3.     Radeon Series

Mach Series were introduced when GUI 2D was first time presented in Windows.

Rage Series - 3D graphics enhancement were introduced after Mach Series.

Radeon Series - it was introduced in yeah 2000 for the better graphical performance.

Nowadays every computer is provided with Graphic Cards. Before buying any graphics card following things should be observed. Memory should be enough, GPU should be enough fast to run heavy games, should meet the latest technology. In my next post I'll explain which things we need to know before buying graphics card.

2D, or two dimensional graphics are the kind of graphics displayed when you use a web browser, check email or work on a spreadsheet. For 2D graphics the major factors are resolution and refresh rate. 

Resolution determines how many little dots are used to draw the image on the screen.
3D or three dimensional graphics are what all first-person-shooter type games use. The value of a good 3D graphics card is that it offloads most of this work from the computer's main processor and a specialized processor on the graphics card handles these calculations. This allows for faster, slicker looking graphics. Also, newer 3D cards handle all kinds of additional functions that gives surfaces texture, make water transparent, etc

How do you measure the speed of a graphics card?

Measuring the speed of the graphics card is a lot more difficult than with the CPU or RAM or even the hard disk. There are many factors which affect how quickly the graphics card can do its job. Many of these only come into play when the graphics card is undertaking certain tasks.

Core clock speed - Much the same as the way you measure the speed of a CPU. The core speed of the Graphics card is measured in MHz and represents the amount of clock cycles the graphics process can do per second. This is a good but not definitive way of telling how fast the graphics card is.

Memory clock speed - Exactly the same of as the core clock speed, except of course that it is for the memory of the graphics card and not the core. This is just as important as the core speed as the memory contains textures that need to be applied to the pixels.

Pixel Pipelines - The amount of pixel pipelines a graphics card has can have a great impact on the speed of the image rendering. This is all about pixel pushing power. A card with 8 pipelines can process twice as many pixels as a card of the same core speed and 4 pipelines.

Textures per pipeline - This only come into effect when multiple textures are needed on the one pixel. Simply put if a multiple texture is needed, then a graphics card with more textures per pipeline will be quicker. On single textured pixels the amount of textures per pipeline will have no effect.

.

Graphics Card

 Graphics Card 

What is Graphic Card

Graphics Card is the device which enables our computers or mobiles to show the enhanced graphical details. To represent real time environment in computer or mobile we need high end details with high definitions, graphic card enables us to do this job perfectly.

Technically speaking, graphic card ( GPU - Graphical Processing Unit ) contains its own processor and memory to run high definition image details. There are many vendors who are providing these graphics cards like nVidia and ATI. These both companies are main rivals in graphics card manufacturing and designing.

Technologies on the basis these graphic cards are designed, Open GL and Direct X. Open GL is open source Graphics support, where as DirectX is Microsoft's created standard and rules.

Electronics Specifications - TV - LCD - Computers

·         The LG Corporation has worked hard to attain full HD 1080p HDTVs with TruMotion technologies in inexpensive cost. The LG Electronics42LW5300 42-Inches 3D LED TV is one particular of these TVs, it has plethora for capabilities.

 

UNIX

What Is UNIX?

• UNIX is an operating system. 
• The job of an operating system is to orchestrate the various parts of the computer -- the processor, the on-board memory, the disk drives, keyboards, video monitors, etc. -- to perform useful tasks. 
• The operating system is the master controller of the computer, the glue that holds together all the components of the system, including the administrators, programmers, and users. 
• 
  
• More than anything else, the operating system gives the computer its recognizable characteristics. 
• It would be difficult to distinguish between two completely different computers, if they were running the same operating system. 
• Conversely, two identical computers, running different operating systems, would appear completely different to the user.
• UNIX was created in the late 1960s, in an effort to provide a multiuser, multitasking system for use by programmers. 
• The philosophy behind the design of UNIX was to provide simple, yet powerful utilities that could be pieced together in a flexible manner to perform a wide variety of tasks.
• The UNIX operating system comprises three parts: The kernel, the standard utility programs, and the system configuration files.

The kernel

• The kernel is the core of the UNIX operating system. 
• Basically, the kernel is a large program that is loaded into memory when the machine is turned on, and it controls the allocation of hardware resources from that point forward. 
• The kernel knows what hardware resources are available (like the processor(s), the on-board memory, the disk drives, network interfaces, etc.), and it has the necessary programs to talk to all the devices connected to it.

The standard utility programs

• These programs include simple utilities like cp, which copies files, and complex utilities, like the shell that allows you to issue commands to the operating system.

The system configuration files

• The system configuration files are read by the kernel, and some of the standard utilities. The UNIX kernel and the utilities are flexible programs, and certain aspects of their behavior can be controlled by changing the standard configuration files. 
• One example of a system configuration file is the filesystem table "fstab" , which tells the kernel where to find all the files on the disk drives. 
• Another example is the system log configuration file "syslog.conf", which tells the kernel how to record the various kinds of events and errors it may encounter.

Types of Routers

Types of Routers

what is broadband connection in communication networks?

Broadband is a high-capacity high-speed Data transmission medium.

This can be done on a single cable by establishing different bandwidth channels.

Broadband technology can be used to transmit voice, data and video over long distances simultaneously.

Routers

Routers capture the information that come through broadband connection via a modem and deliver it to your computer.

The router choose route for the packet so that you receive the information Firstly.

Types of Routers

There are several types of routers.Namely,

 Broadband Routers

Wireless Routers

Other Type of Router

Edge Router

Subscriber Edge Router

Inter-provider Border Router

Core Router

Wired and Wireless Routers.

Broadband Routers

Broadband routers can do different types of things.

Broadband routers can be used to connect computers or to connect to the Internet.

 If you connect to the internet through phone and using Voice over IP technology (VOIP) then you need broadband router.

These are often a special type of modem (ADSL) that will have both Ethernet and phone jacks.

Wireless Routers

Wireless routers create a wireless signal in your home or office.

So, any PC within range of Wireless routers can connect it and use your Internet.

In order to secure your Wireless routers, you simply need to come secure it with password or get your IP address.

Then, you'll log on into your router with the user ID and passwords will that come with your router.

Other Type of Router

Edge Router

This type of router are placed at the edge of the ISP network, the are normally configured to external protocol like BGP (Border gateway protocol) to another BGP of other ISP or large organisation.

Subscriber Edge Router

This type of router belongs to an end user (enterprise) organization.

It’s configured to  broadcast external BGP to it’s provider’s AS(s)

Inter-provider Border Router

This type of router is  for Interconnecting ISPs, this is a BGP speaking router that maintains BGP sessions with other BGP speaking routers in other providers' ASes.

Core Router

A router that resides within the middle or backbone of the LAN network rather than at its periphery.

In some instances , a core router provides a stepdown backbone , interconnecting the distribution routers from multiple building of a campus ( LAN), or Large enterprise Location (WAN).

They tend to be optimized for a high brandwidth.

Wired and Wireless Routers.

Home and small office networking is becoming popular by day by the use of IP wired and wireless router.

Wired and wireless router are able to maintain routing and configuration information in their routing table. 

They also provide the service of filtering traffic of incoming and outgoing packets based on IP addresses.

 Some wireless routers combines the functions of router with those of a network switch and that of a firewall in one.

Different Architectures for Clusters

Different Architectures for Clusters

Different Architectures

Clusters follow general guidelines for different applications. 

Database Replication - MySQL database replication cluster as a backend for a website.
Batch Processing - When many tasks need scheduling.
Render Farm - Distributed rendering cluster configuration.
Software Development Architecture - Compile Farm - Clusters for software development.
Message Passing Architectures - Essentially Supercomputers for true high performance applications.

Database Replication Clusters

Database replication is a necessary and useful application of clusters. Many databases are read intensive with many more read requests made than write requests. By replicating the data across a community of nodes it is possible to scale the number of read requests which can be dealt with per second in a linear fashion.

A website has large amounts of content all stored in a MySQL database. The web servers (which are also probably clustered), make read requests from the replication nodes through a load balancer. Write requests are sent to the master node.

Multi master configurations are also common. In situations with high levels of writes it is necessary to be creative with the architecture of the database to allow replication between masters or partition the database such that there are essentially two separate databases for different queries. For example one database for searches and another for user data.

Batch Processing

Batch processing systems are key in the banking industry. Good scheduling and rapid response are important if for example we are not to be kept waiting at the cash point as our bank checks we have the money in our account we just asked for.

Sometimes referred to as compute farm, the key part of batch processing systems is maximising up time and maintaining performance at peak load while minimising cost levels.

In this sort of situation it can be wise to save money by reducing capcity during low demand by shutting down some nodes and bringing them back up when demand will be high. To maximise efficiency a intelligent Workload Management System (WMS) should be implemented.

Render Farms

Render farms are a special form of batch processing clusters, with less of an emphasis on responsiveness - most of the processing jobs will take more than a minute. Low cost hardware and the quantity of available processing power is most important. Rendering is used in the visual effects, computer modelling and CGI industries and refers to the process of creating an image from what are essentially mathematical formulae. Rendering engines provide numerous different features, which in combination can produce a scene with the desired effects.

Where is Rendering Found

§  Computer Aided Design (CAD), in engineering and design.

§  Visual Effects (VFX), for film, television and advertising.

§  Architectural Rendering, for visualising buildings, rooms and landscapes.

One of the most intensive aspects of these processes is in producing photo realistic scenes and animations. This is where clusters come into their own.

Cluster Computing

Cluster Computing

What Is Cluster Computing?

• Consists of many of the same or similar type of machines
  (Heterogenous clusters are a subtype, still mostly experimental)
• Tightly-coupled using dedicated network connections
• All machines share resources such as a common home directory
  (NFS can be a problem in very large clusters, so binaries and data must be pushed to scratch on each node.)
• They must trust each other so that rsh or ssh does not require a password,
  otherwise you would need to do a manual start on each machine.
• Must have software such as an MPI implementation installed to allow programs to be run across all nodes

Shared Disk Clusters

One approach to clustering utilizes central I/O devices accessible to all computers within the cluster. We call these systems shared-disk clusters as the I/O involved is typically disk storage for normal files and/or databases. Shared-disk cluster technologies include Oracle Parallel Server (OPS)and IBM's HACMP.

Shared-disk clusters rely on a common I/O bus for disk access but do not require shared memory. Because all nodes may concurrently write to or cache data from the central disks, a synchronization mechanism must be used to preserve coherence of the system. An independent piece of cluster software called the "distributed lock manager" assumes this role.

Shared-disk clusters support higher levels of system availability: if one node fails, other nodes need not be affected. However, higher availability comes at a cost of somewhat reduced performance in these systems because of overhead in using a lock manager and the potential bottlenecks of shared hardware generally. Shared-disk clusters make up for this shortcoming with relatively good scaling properties: OPS and HACMP support eight-node systems, for example.

Shared Nothing Clusters

A second approach to clustering is dubbed shared-nothing because it does not involve concurrent disk accesses from multiple nodes. (In other words, these clusters do not require a distributed lock manager.) Shared-nothing cluster solutions include Microsoft Cluster Server (MSCS).

MSCS is an atypical example of a shared nothing cluster in several ways. MSCS clusters use a shared SCSI connection between the nodes, that naturally leads some people to believe this is a shared-disk solution. But only one server (the one that owns the quorum resource) needs the disks at any given time, so no concurrent data access occurs. MSCS clusters also typically include only two nodes, whereas shared nothing clusters in general can scale to hundreds of nodes.

Mirrored Disk Clusters

Mirrored-disk cluster solutions include Legato's Vinca. Mirroring involves replicating all application data from primary storage to a secondary backup (perhaps at a remote location) for availability purposes. Replication occurs while the primary system is active, although the mirrored backup system -- as in the case of Vinca -- typically does not perform any work outside of its role as a passive standby. If a failure occurs in the primary system, a failover process transfers control to the secondary system. Failover can take some time, and applications can lose state information when they are reset, but mirroring enables a fairly fast recovery scheme requiring little operator intervention. Mirrored-disk clusters typically include just two nodes.

Oracle DataTypes

Character Datatypes

The following are the Character Datatypes in Oracle/PLSQL:

Data Type Syntax	Oracle 9i	Oracle 10g	Oracle 11g	Explanation (if applicable)
char(size)	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Where size is the number of characters to store. Fixed-length strings. Space padded.
nchar(size)	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Where size is the number of characters to store. Fixed-length NLS string Space padded.
nvarchar2(size)	Maximum size of 4000 bytes.	Maximum size of 4000 bytes.	Maximum size of 4000 bytes.	Where size is the number of characters to store. Variable-length NLS string.
varchar2(size)	Maximum size of 4000 bytes. Maximum size of 32KB in PLSQL.	Maximum size of 4000 bytes. Maximum size of 32KB in PLSQL.	Maximum size of 4000 bytes. Maximum size of 32KB in PLSQL.	Where size is the number of characters to store. Variable-length string.
long	Maximum size of 2GB.	Maximum size of 2GB.	Maximum size of 2GB.	Variable-length strings. (backward compatible)
raw	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Maximum size of 2000 bytes.	Variable-length binary strings
long raw	Maximum size of 2GB.	Maximum size of 2GB.	Maximum size of 2GB.	Variable-length binary strings. (backward compatible)

Numeric Datatypes

The following are the Numeric Datatypes in Oracle/PLSQL:

Data Type Syntax	Oracle 9i	Oracle 10g	Oracle 11g	Explanation (if applicable)
number(p,s)	Precision can range from 1 to 38. Scale can range from -84 to 127.	Precision can range from 1 to 38. Scale can range from -84 to 127.	Precision can range from 1 to 38. Scale can range from -84 to 127.	Where p is the precision and s is the scale. For example, number(7,2) is a number that has 5 digits before the decimal and 2 digits after the decimal.
numeric(p,s)	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Where p is the precision and s is the scale. For example, numeric(7,2) is a number that has 5 digits before the decimal and 2 digits after the decimal.
float
dec(p,s)	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Where p is the precision and s is the scale. For example, dec(3,1) is a number that has 2 digits before the decimal and 1 digit after the decimal.
decimal(p,s)	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Precision can range from 1 to 38.	Where p is the precision and s is the scale. For example, decimal(3,1) is a number that has 2 digits before the decimal and 1 digit after the decimal.
integer
int
smallint
real
double precision

Date/Time Datatypes

The following are the Date/Time Datatypes in Oracle/PLSQL:

Data Type Syntax	Oracle 9i	Oracle 10g	Oracle 11g	Explanation (if applicable)
date	A date between Jan 1, 4712 BC and Dec 31, 9999 AD.	A date between Jan 1, 4712 BC and Dec 31, 9999 AD.	A date between Jan 1, 4712 BC and Dec 31, 9999 AD.
timestamp (fractional seconds precision)	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	Includes year, month, day, hour, minute, and seconds. For example: timestamp(6)
timestamp (fractional seconds precision) with time zone	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	Includes year, month, day, hour, minute, and seconds; with a time zone displacement value. For example: timestamp(5) with time zone
timestamp (fractional seconds precision) with local time zone	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	fractional seconds precision must be a number between 0 and 9. (default is 6)	Includes year, month, day, hour, minute, and seconds; with a time zone expressed as the session time zone. For example: timestamp(4) with local time zone
interval year (year precision) to month	year precision is the number of digits in the year. (default is 2)	year precision is the number of digits in the year. (default is 2)	year precision is the number of digits in the year. (default is 2)	Time period stored in years and months. For example: interval year(4) to month
interval day (day precision) to second (fractional seconds precision)	day precision must be a number between 0 and 9. (default is 2) fractional seconds precision must be a number between 0 and 9. (default is 6)	day precision must be a number between 0 and 9. (default is 2) fractional seconds precision must be a number between 0 and 9. (default is 6)	day precision must be a number between 0 and 9. (default is 2) fractional seconds precision must be a number between 0 and 9. (default is 6)	Time period stored in days, hours, minutes, and seconds. For example: interval day(2) to second(6)

Large Object (LOB) Datatypes

The following are the LOB Datatypes in Oracle/PLSQL:

Data Type Syntax	Oracle 9i	Oracle 10g	Oracle 11g	Explanation (if applicable)
bfile	Maximum file size of 4GB.	Maximum file size of 232-1 bytes.	Maximum file size of 264-1 bytes.	File locators that point to a binary file on the server file system (outside the database).
blob	Store up to 4GB of binary data.	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage).	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage).	Stores unstructured binary large objects.
clob	Store up to 4GB of character data.	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character data.	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character data.	Stores single-byte and multi-byte character data.
nclob	Store up to 4GB of character text data.	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character text data.	Store up to (4 gigabytes -1) * (the value of the CHUNK parameter of LOB storage) of character text data.	Stores unicode data.

Rowid Datatypes

The following are the Rowid Datatypes in Oracle/PLSQL:

Data Type Syntax	Oracle 9i	Oracle 10g	Oracle 11g	Explanation (if applicable)
rowid	The format of the rowid is: BBBBBBB.RRRR.FFFFF Where BBBBBBB is the block in the database file; RRRR is the row in the block; FFFFF is the database file.	The format of the rowid is: BBBBBBB.RRRR.FFFFF Where BBBBBBB is the block in the database file; RRRR is the row in the block; FFFFF is the database file.	The format of the rowid is: BBBBBBB.RRRR.FFFFF Where BBBBBBB is the block in the database file; RRRR is the row in the block; FFFFF is the database file.	Fixed-length binary data. Every record in the database has a physical address or rowid.
urowid(size)				Universal rowid. Where size is optional.