What is immersive multimedia?

These terms refer to computer-generated simulation of reality with physical, spatial and visual dimensions. This interactive technology is used by architects, science and engineering researchers, and the arts, entertainment and video games industry.

 

Virtual reality systems can simulate everything from a walk-through of a building prior to construction to simulations of aircraft flight and three dimensional computer games.

 

Immersive technologies and virtual reality are powerful and compelling computer applications by which humans can interface and interact with computer generated environments in a way that mimics real life sense engagement.

 

Although mostly known for its application in the entertainment industry the real promise lies in such fields as medicine, science, engineering, oil exploration, data visualization and the military to name just a few.

 

As 3D and immersive technology becomes more integrated and available for a wide range of applications. It l requires well-designed user interfaces and innovative content for the next generation of computer games and integrated technology like mobile devices, distributed web systems and desktop applications.

Core concepts.......

Core concepts

At their core, all models of ubiquitous computing share a vision of small, inexpensive, robust networked processing devices, distributed at all scales throughout everyday life and generally turned to distinctly common-place ends. For example, a domestic ubiquitous computing environment might interconnect lighting and environmental controls with personal biometric monitors woven into clothing so that illumination and heating conditions in a room might be modulated, continuously and imperceptibly. Another common scenario posits refrigerators "aware" of their suitably tagged contents, able to both plan a variety of menus from the food actually on hand, and warn users of stale or spoiled food.
Ubiquitous computing presents challenges across computer science: in systems design and engineering, in systems modelling, and in user interface design. Contemporary human-computer interaction models, whether command-line, menu-driven, or GUI-based, are inappropriate and inadequate to the ubiquitous case. This suggests that the "natural" interaction paradigm appropriate to a fully robust ubiquitous computing has yet to emerge - although there is also recognition in the field that in many ways we are already living in an ubicomp world. Contemporary devices that lend some support to this latter idea include mobile phones, digital audio players, radio-frequency identification tags, GPS, and interactive whiteboards.
Mark Weiser proposed three basic forms for ubiquitous system devices, see also Smart device: tabs, pads and boards.

• Tabs: wearable centimetre sized devices
• Pads: hand-held decimetre-sized devices
• Boards: metre sized interactive display devices.

These three forms proposed by Weiser are characterized by being macro-sized, having a planar form and on incorporating visual output displays. If we relax each of these three characteristics we can expand this range into a much more diverse and potentially more useful range of Ubiquitous Computing devices. Hence, three additional forms for ubiquitous systems have been proposed:^[5]

• Dust: miniaturized devices can be without visual output displays, e.g., Micro Electro-Mechanical Systems (MEMS), ranging from nanometres through micrometers to millimetres. See also Smart dust.
• Skin: fabrics based upon light emitting and conductive polymers, organic computer devices, can be formed into more flexible non-planar display surfaces and products such as clothes and curtains, see OLED display. MEMS device can also be painted onto various surfaces so that a variety of physical world structures can act as networked surfaces of MEMS.
• Clay: ensembles of MEMS can be formed into arbitrary three dimensional shapes as artefacts resembling many different kinds of physical object (see also Tangible interface).

In his book The Rise of the Network Society, Manuel Castells suggests that there is an ongoing shift from already-decentralised, stand-alone microcomputers and mainframes towards entirely pervasive computing. In his model of a pervasive computing system, Castells uses the example of the Internet as the start of a pervasive computing system. The logical progression from that paradigm is a system where that networking logic becomes applicable in every realm of daily activity, in every location and every context. Castells envisages a system where billions of miniature, ubiquitous inter-communication devices will be spread worldwide, "like pigment in the wall paint".

History

Mark Weiser coined the phrase "ubiquitous computing" around 1988, during his tenure as Chief Technologist of the Xerox Palo Alto Research Center (PARC). Both alone and with PARC Director and Chief Scientist John Seely Brown, Weiser wrote some of the earliest papers on the subject, largely defining it and sketching out its major concerns.^[6][7][8]
Recognizing that the extension of processing power into everyday scenarios would necessitate understandings of social, cultural and psychological phenomena beyond its proper ambit, Weiser was influenced by many fields outside computer science, including "philosophy, phenomenology, anthropology, psychology, post-Modernism, sociology of science and feminist criticism." He was explicit about "the humanistic origins of the ‘invisible ideal in post-modernist thought'",^[8] referencing as well the ironically dystopian Philip K. Dick novel Ubik.
Dr. Ken Sakamura of University of Tokyo, Japan leads the Ubiquitous Networking Laboratory (UNL), Tokyo as well as the T-Engine Forum. The joint goal of Sakamura's Ubiquitous Networking specification and the T-Engine forum, is to enable any everyday device to broadcast and receive information.^[9][10]
MIT has also contributed significant research in this field, notably Things That Think consortium (directed by Hiroshi Ishii, Joseph A. Paradiso and Rosalind Picard) at the Media Lab^[11] and the CSAIL effort known as Project Oxygen.^[12] Other major contributors include Georgia Tech's College of Computing, NYU's Interactive Telecommunications Program, UC Irvine's Department of Informatics, Microsoft Research, Intel Research and Equator,^[13] Ajou University UCRi & CUS.^[14]

Pervasive Computing ( Ubiquitous Computing )

Contents  [hide]

Pervasive computing (also called ubiquitous computing) is the growing trend towards embedding microprocessors in everyday objects so they can communicate information.  The words pervasive and ubiquitous mean "existing everywhere." Pervasive computing devices are completely connected and constantly available. 

Pervasive computing relies on the convergence of  wireless technologies, advanced electronics and the Internet. The goal of researchers working in pervasive computing is to create smart products that communicate unobtrusively. The products are connected to the Internet and the data they generate is easily available.  

Privacy advocates are concerned about the "big brother is watching you" aspects of pervasive computing, but from a practical standpoint, most researchers feel it will improve efficiency.  In a 1996 speech, Rick Belluzo, who was then executive VP and general manager of Hewlett-Packard, compared pervasive computing to electricity. He described it as being "the stage when we take computing for granted. We only notice its absence, rather than its presence."

An example of a practical application of pervasive computing is the replacement of old electric meters with smart meters. In the past, electric meters had to be manually read by a company representative. Smart meters report usage in real-time over the Internet.  They will also notify the power company when there is an outage, reset thermostats according to the  homeowner's directives, send messages to display units in the home and regulate the water heater.

Ubiquitous computing (ubicomp) is a post-desktop model of human-computer interaction in which information processing has been thoroughly integrated into everyday objects and activities. In the course of ordinary activities, someone "using" ubiquitous computing engages many computational devices and systems simultaneously, and may not necessarily even be aware that they are doing so. This model is usually considered an advancement from the desktop paradigm. More formally, ubiquitous computing is defined as "machines that fit the human environment instead of forcing humans to enter theirs."^[1]

This paradigm is also described as pervasive computing, ambient intelligence,^[2] or, more recently, everyware,^[3] where each term emphasizes slightly different aspects. When primarily concerning the objects involved, it is also physical computing, the Internet of Things, haptic computing,^[4] and things that think. Rather than propose a single definition for ubiquitous computing and for these related terms, a taxonomy of properties for ubiquitous computing has been proposed, from which different kinds or flavors of ubiquitous systems and applications can be described.^[5]

Hybrid

Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network

• A Star ring network consists of two or more star topologies connected using a multistation access unit (MAU) as a centralized hub.
• A Star Bus network consists of two or more star topologies connected using a bus trunk (the bus trunk serves as the network's backbone).

While grid and torus networks have found popularity in high-performance computing applications, some systems have used genetic algorithms to design custom networks that have the fewest possible hops in between different nodes. Some of the resulting layouts are nearly incomprehensible, although they function quite well.^{[citation needed]}
A Snowflake topology is really a "Star of Stars" network, so it exhibits characteristics of a hybrid network topology but is not composed of two different basic network topologies being connected. Definition : Hybrid topology is a combination of Bus,Star and ring topology.

Daisy chain

Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.

• A linear topology puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
• By connecting the computers at each end, a ring topology can be formed. An advantage of the ring is that the number of transmitters and receivers can be cut in half, since a message will eventually loop all of the way around. When a node sends a message, the message is processed by each computer in the ring. If a computer is not the destination node, it will pass the message to the next node, until the message arrives at its destination. If the message is not accepted by any node on the network, it will travel around the entire ring and return to the sender. This potentially results in a doubling of travel time for data.

Centralization

The star topology reduces the probability of a network failure by connecting all of the peripheral nodes (computers, etc.) to a central node. When the physical star topology is applied to a logical bus network such as Ethernet, this central node (traditionally a hub) rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the remaining peripheral nodes will be unaffected. However, the disadvantage is that the failure of the central node will cause the failure of all of the peripheral nodes also,

If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way round trip transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.

A tree topology (a.k.a. hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. This tree has individual peripheral nodes (e.g. leaves) which are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the functionality of the central node may be distributed.
As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.

To alleviate the amount of network traffic that comes from broadcasting all signals to all nodes, more advanced central nodes were developed that are able to keep track of the identities of the nodes that are connected to the network. These network switches will "learn" the layout of the network by "listening" on each port during normal data transmission, examining the data packets and recording the address/identifier of each connected node and which port it is connected to in a lookup table held in memory. This lookup table then allows future transmissions to be forwarded to the intended destination only.

Decentralization

In a mesh topology (i.e., a partially connected mesh topology), there are at least two nodes with two or more paths between them to provide redundant paths to be used in case the link providing one of the paths fails. This decentralization is often used to advantage to compensate for the single-point-failure disadvantage that is present when using a single device as a central node (e.g., in star and tree networks). A special kind of mesh, limiting the number of hops between two nodes, is a hypercube. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful. This is similar in some ways to a grid network, where a linear or ring topology is used to connect systems in multiple directions. A multi-dimensional ring has a toroidal topology, for instance.

A fully connected network, complete topology or full mesh topology is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are n(n-1)/2 direct links. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in military applications.

Bus

Main article: Bus network

In local area networks where bus topology is used, each node is connected to a single cable. Each computer or server is connected to the single bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data matches the machine address, the data is accepted. Since the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, since only one cable is utilized, it can be the single point of failure. If the network cable is terminated on both ends and when without termination data transfer stop and when cable breaks, the entire network will be down.

Linear bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the 'bus', which is also commonly referred to as the backbone, or trunk) – all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.^[1]

Note: The two endpoints of the common transmission medium are normally terminated with a device called a terminator that exhibits the characteristic impedance of the transmission medium and which dissipates or absorbs the energy that remains in the signal to prevent the signal from being reflected or propagated back onto the transmission medium in the opposite direction, which would cause interference with and degradation of the signals on the transmission medium.

Distributed bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has more than two endpoints that are created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology (i.e., all nodes share a common transmission medium).

Notes:

1. All of the endpoints of the common transmission medium are normally terminated using 50 ohm resistor.
2. The linear bus topology is sometimes considered to be a special case of the distributed bus topology – i.e., a distributed bus with no branching segments.
3. The physical distributed bus topology is sometimes incorrectly referred to as a physical tree topology – however, although the physical distributed bus topology resembles the physical tree topology, it differs from the physical tree topology in that there is no central node to which any other nodes are connected, since this hierarchical functionality is replaced by the common bus.

 Star

Main article: Star network

In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure.

Notes

1. A point-to-point link (described above) is sometimes categorized as a special instance of the physical star topology – therefore, the simplest type of network that is based upon the physical star topology would consist of one node with a single point-to-point link to a second node, the choice of which node is the 'hub' and which node is the 'spoke' being arbitrary.^[1]
2. After the special case of the point-to-point link, as in note (1) above, the next simplest type of network that is based upon the physical star topology would consist of one central node – the 'hub' – with two separate point-to-point links to two peripheral nodes – the 'spokes'.
3. Although most networks that are based upon the physical star topology are commonly implemented using a special device such as a hub or switch as the central node (i.e., the 'hub' of the star), it is also possible to implement a network that is based upon the physical star topology using a computer or even a simple common connection point as the 'hub' or central node.^{[citation needed]}
4. Star networks may also be described as either broadcast multi-access or nonbroadcast multi-access (NBMA), depending on whether the technology of the network either automatically propagates a signal at the hub to all spokes, or only addresses individual spokes with each communication.

Extended star

A type of network topology in which a network that is based upon the physical star topology has one or more repeaters between the central node (the 'hub' of the star) and the peripheral or 'spoke' nodes, the repeaters being used to extend the maximum transmission distance of the point-to-point links between the central node and the peripheral nodes beyond that which is supported by the transmitter power of the central node or beyond that which is supported by the standard upon which the physical layer of the physical star network is based.

If the repeaters in a network that is based upon the physical extended star topology are replaced with hubs or switches, then a hybrid network topology is created that is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.

Distributed Star

A type of network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').

 Ring

Main article: Ring network

A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.^[4]

 Mesh

Fully connected

The number of connections in a full mesh = n(n - 1) / 2.

Note: The physical fully connected mesh topology is generally too costly and complex for practical networks, although the topology is used when there are only a small number of nodes to be interconnected (see Combinatorial explosion).

Partially connected

Partially connected mesh topology

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Note: In most practical networks that are based upon the partially connected mesh topology, all of the data that is transmitted between nodes in the network takes the shortest path between nodes,^{[citation needed]} except in the case of a failure or break in one of the links, in which case the data takes an alternative path to the destination. This requires that the nodes of the network possess some type of logical 'routing' algorithm to determine the correct path to use at any particular time.

 Tree

Tree network topology

This section may be confusing or unclear to readers. Please help clarify the section; suggestions may be found on the talk page. (June 2011)

The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node, while each of the second level nodes that are connected to the top level central 'root' node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central 'root' node being the only node that has no other node above it in the hierarchy (The hierarchy of the tree is symmetrical.) Each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number, being referred to as the 'branching factor' of the hierarchical tree.This tree has individual peripheral nodes.

1. A network that is based upon the physical hierarchical topology must have at least three levels in the hierarchy of the tree, since a network with a central 'root' node and only one hierarchical level below it would exhibit the physical topology of a star.
2. A network that is based upon the physical hierarchical topology and with a branching factor of 1 would be classified as a physical linear topology.
3. The branching factor, f, is independent of the total number of nodes in the network and, therefore, if the nodes in the network require ports for connection to other nodes the total number of ports per node may be kept low even though the total number of nodes is large – this makes the effect of the cost of adding ports to each node totally dependent upon the branching factor and may therefore be kept as low as required without any effect upon the total number of nodes that are possible.
4. The total number of point-to-point links in a network that is based upon the physical hierarchical topology will be one less than the total number of nodes in the network.
5. If the nodes in a network that is based upon the physical hierarchical topology are required to perform any processing upon the data that is transmitted between nodes in the network, the nodes that are at higher levels in the hierarchy will be required to perform more processing operations on behalf of other nodes than the nodes that are lower in the hierarchy. Such a type of network topology is very useful and highly recommended.

definition : Tree topology is a combination of Bus and Star topology.

Point-to-point.....

The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law.

Permanent (dedicated)

Easiest to understand, of the variations of point-to-point topology, is a point-to-point communications channel that appears, to the user, to be permanently associated with the two endpoints. A children's tin can telephone is one example of a physical dedicated channel.

Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. "Nailing down" a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio.

Switched:

Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically, and dropped when no longer needed. This is the basic mode of conventional telephony.

Topology.....

There are two basic categories of network topologies:

 1 Physical topologies     2 Logical topologies
The shape of the cabling layout used to link devices is called the physical topology of the network. This refers to the layout of cabling, the locations of nodes, and the interconnections between the nodes and the cabling.

The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunications circuits.

The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. A network's logical topology is not necessarily the same as its physical topology. For example, the original twisted pair Ethernet using repeater hubs was a logical bus topology with a physical star topology layout. Token Ring is a logical ring topology, but is wired a physical star from the Media Access Unit.

The logical classification of network topologies generally follows the same classifications as those in the physical classifications of network topologies but describes the path that the data takes between nodes being used as opposed to the actual physical connections between nodes. The logical topologies are generally determined by network protocols as opposed to being determined by the physical layout of cables, wires, and network devices or by the flow of the electrical signals, although in many cases the paths that the electrical signals take between nodes may closely match the logical flow of data, hence the convention of using the terms logical topology and signal topology interchangeably.

Logical topologies are often closely associated with Media Access Control methods and protocols. Logical topologies are able to be dynamically reconfigured by special types of equipment such as routers and switches.

The study of network topology recognizes eight basic topologies:^[5]

• Point-to-point
• Bus
• Star
• Ring or circular
• Mesh
• Tree
• Hybrid
• Daisy chain

Network topology ..............

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer or biological network.Network topologies may be physical or logical.Physical topology refers to the physical design of a network including the devices, location and cable installation.

 Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.


Topology can be understood as the shape or structure of a network. This shape does not necessarily correspond to the actual physical design of the devices on the computer network. The computers on a home network can be arranged in a circle but it does not necessarily mean that it represents a ring topology.

Any particular network topology is determined only by the graphical mapping of the configuration of physical and/or logical connections between nodes. The study of network topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types may differ in two networks and yet their topologies may be identical.

A local area network (LAN) is one example of a network that exhibits both a physical topology and a logical topology. Any given node in the LAN has one or more links to one or more nodes in the network and the mapping of these links and nodes in a graph results in a geometric shape that may be used to describe the physical topology of the network.

Likewise, the mapping of the data flow between the nodes in the network determines the logical topology of the network. The physical and logical topologies may or may not be identical in any particular network.

Maintain your PC ~.~"

The tools

With Windows XP, Microsoft has done two things to make it easier to maintain a PC. It's easier to find the tools to do it with, and "Help" for using them is much better. There are two easy ways to find the tools. I recommend using "Help & Support" the first time you use the tools. The Windows Explorer route will be quicker after that.

From Windows Explorer

Open a Windows Explorer window. Right-click the "disk" (hard drive) you want to maintain. Choose "Properties". The properties dialog-box will open at the "General" tab. Click the "Disk Cleanup" button to get the "Disk Cleanup" tool.

With the properties dialog-box still open, click the "Tools" tab. You'll see the "Error-checking" and "Defragmention tools" right there.

From Help & Support

Click "Start", then "Help & Support". Enter "disk" and click the green arrow. You'll find "Using Disk Cleanup", "Using Disk Defragmenter" and "Detecting and repairing disk errors" in the left hand "Search Results" pane. Each of them will tell you how to access and use the corresponding tool.

 

1. Back up your files (and system)

The maintenance tools you're going to use are going to do some very "heavy lifting". You never know what's going to get dropped. Do yourself a big favor. Back up your critical files, and preferrably, back up your entire system first.

2. Clean up your hard drive

Start your maintenance work with Disk Cleanup. It will make error checking and defragmenting go better and faster, because there's less junk for the tools to deal with. You might want to go further and do some basic cleanup before you start the rest of your maintenance. PC World has two good articles on this topic. [one] [two]
Deleting program files is an error that neophytes often make. Programs should always be uninstalled, which is quite different. To uninstall use: "Start" > "Control Panel" > "Add and Remove Programs". Find the program in the list and delete it. After you've done that, some files may remain in the program's folder, which is usually in C:\Program Files\Name (name of the program you just installed). It's OK to delete the files and folder now.

3. Detect and repair disk errors

Disk error checking was called ScanDisk in Windows 98. It's a good idea to check for errors about once a month to keep your system running well. The tool can find and fix errors in the file allocation table, the file system structure (lost clusters, crosslinked files) and the directory tree structure. It can also detect and isolate sectors that have gone bad because of damage to the surface of your disk.
When you click "Start" the tool will tell you, "The disk check could not be performed... Do you want to schedule this disk check to occur the next time you restart the computer? Click "Yes".
If you begin to see defective sectors in the report, especially a growing number, you may want to replace your hard drive before it crashes and dies. At the very least bad sectors should motivate you to be very disciplined about backing up your work.

4. Defragment your hard drive

You should defragment your hard drive on a regular basis -- every three months is good -- to keep your system running well. In the course of normal usage, files are constantly changed and written or rewritten to the hard drive. The file system tries to pack the files tightly. It breaks them into pieces to fit where it finds space for them. Over time these pieces get scattered all over the drive. It begins to take a lot of head movement (and thus time) to read and write files. As a result, your computer's performance suffers, and worse yet, it's easier for errors to creep in.

Before you defrag

• Clean out any junk files that you don't need. Empty the recycle bin, delete the contents of C:\Temp\ and C:\Windows\Temp, and delete your temporary internet files ["Tools" > "Internet Options" > "Delete files..."]. You might want to use Disk Cleanup to clean out more junk.
• If you have a virus program, turn off "auto-protect" or close the program. Otherwise it will very likely interfere with Disk Defragmenter.
• Disable your screensaver Right click the Desktop > select "Properties" > click the "Screen Saver" tab > select "none" > and click "OK".
• You may need to disable, or exit other programs too. (Use the "3-fingered salute" -- Ctrl+Alt+Delete -- to shut down unnecessary programs.)
• It's a good idea to check your disk for errors just before you defrag. The defrag tool will look for disk errors but it can't fix them itself. If there are errors, you'll end up using the error checking tool, and trying defrag again.

Do not run defrag if there's a chance that electrical power will be interrupted -- for example, during a thunderstorm, or when construction could cause an outage. Defrag will be unable to complete what it was in the middle of and your hard drive will probably be scrambled.
Don't use the automatic mode to defrag a laptop. Some day you're going to forget to plug it in, defrag will start, the battery will run down, and you'll lose all your data and get to reinstall everything.

5. Good housekeeping

Cleaning your PC is part of the maintenance job. Computers aren't big enough for dust bunnies, but they collect a lot more fuzz than you might imagine. It can eventually cause overheating, which is a nemesis for anything electronic. The page on cleaning your PC will help you with this and other "housekeeping" chores.

 

Computer Topics !!!

Get to know your PC

You need to be uninhibited if you want to learn more about using your PC. That's how kids learn to use them so quickly.
"Right-click" is one safe way to explore your PC. Right-click on anything and everything. Right-click means click an object with the right mouse button -- for example, this text -- try it and see what you get.

It's not going to hurt anything. It merely opens a context menu, which is simply a list of options appropriate for the object you right-clicked. Try clicking more objects up at the top of your browser.
Nothing happens until you "left-click" one of the menu options. If you're in doubt about clicking any of them, just left-click anywhere outside the menu and it will close. It's always safe to click "Properties", which gives you access to lots of information and settings.

Have a look around when "Properties" opens. There's always a "Cancel" button that will bail you out of "Properties" with no changes and no damage done. If you do make changes it could adversely affect your computer if you don't know what you're doing.

Start your computers.

Microsoft calls it "starting" your computer, but it's still "boot" to me. Don't confuse "starting" with the "Start" menu. Starting is turning on, starting , or booting your computer. The "bootstrap" method of loading the operating system into computer memory was invented about the same time electronic computers were invented.

I remember loading the first 17 "words" by hand to start one of the first computers I used. Each word was 2 bytes, or 16 bits. You had to set 16 switches and press the 17th to load each word. Using those 17 words (not switches), the computer was able to load another 1000 or so words on its own. They were on a strip of paper tape with holes punched in it -- much like a miniature player piano roll. Primed with those 1000 words, the computer was then able to load the rest of the operating system from a cassette tape.
It took me about 3 minutes to manually boot that old computer. Windows is loaded in a similar way. [more | more yet ] Too bad the process still takes so long, but there is a way to avoid booting your computer every day. The concept has been updated for Windows Vista.

Computing

The basic principles of general purpose computers have not changed since they were first conceived by Charles Babbage sometime before 1833. (His design was not actually built until sometime around 1990 -- yes those dates are correct.)

Computer principles don't change because they are as fundamental as mathematics, which of course don't change either. We're now close to the 60th anniversary of the first electronic computer, which was based on Babbage's original design. The big difference is they are powered by electricity, not steam.
Computer principles are embodied in the primary elements of a computer: input device(s), store (memory), processor, instructions and output device(s). In the beginning there were no hard drives, keyboards or monitors, much less mice. But they fundamentally worked in the same way.
Computer operation is straightforward -- data goes in (input) -- operations on the data are performed, results are stored (intermediate and final) -- the results come out (output). All of this is under the control of instructions (program), which are just another form of data.
For example -- [(2+4) divided by 3]. First the two numbers <2> and <4> are go in. They are added together and the temporary results are stored. The number <3> is then goes in. Next the temporary results <6> are divided by <3> and the results <2> come out. And it's all done in less than a millionth of a second.

The confusing thing about a PC is the multiplicity of input devices, memories, instruction sets, processors and output devices -- most of which are themselves used for multiple functions and tasks in turn. The keyboard, mouse, CD drives, modems and cameras are all input devices. Speakers, printers, the monitor, and modems (again) are common output devices.
Memory is used not only for data and results, but also for instructions. That's where it really gets confusing. The processor can't perform an instruction unless both the current data and the current instruction are in memory.

PCs work with much more data than memory can hold. That's why hard drives were invented. They "store" the data of the past (results), the data of the future (input), and instructions not currently being used. The processor goes to the hard drive to "fetch" data and instructions it needs next, and to "store" results it has completed.

Files

There are two primary types of files used by computers: instruction files and data files. Instruction files are either system (i.e., Windows) or program files. They instruct the processor to store input data, perform operations on the data, and output the results.
Data files may be in the form of documents, object files, data tables, output data or system data. Sound files and image files are examples of object files. Font files are an example of data table files. The "Registry" is the prime example of Windows system data.
All these file types -- data, system, and program -- are mixed together on the hard drive. They are segregated by location (folders) to a large extent, but it's somewhat of a mess. If you want to use a computer effectively, it's a big help to keep the files organized on your computer.
Windows Explorer is your window into the files on your computer. It gives you the big picture, yet you can zoom in and get things done quickly. There are some things you can't do any other way in fact.
Opening a file is a simple example of the efficiency of Windows Explorer. If you navigate to a file with Windows Explorer, a simple "double-click" will open the right program, which will then open the file. The other way is to open the program and then use it's less convenient navigation to open the file.

Backup

Backup is a chore, and people don't like to do chores. You're not likely take backup seriously until you've lost something irreplaceable -- maybe after it's happened twice. A wise person learns from the mistakes of other people though. Our backup pages should help you design and follow a backup strategy that fits your situation.

Computer myths

The most common PC myths are Windows myths. One of the most common is about how Windows uses memory. They persist because they seem logical. Most are relatively harmless, but they cause people to waste time, energy and money.

The virus myth: "You get a computer virus when you download a file to your hard drive". Truth is, not really. Yes, it's like a land mine -- harmless if left alone, but deadly if activated. If you open or install the infected file, the virus will be activated. But it can't do any harm until then.

The preview pane in Outlook Express (or Outlook) provides the grain of truth that perpetuates the download myth. Simply viewing an email in the preview pane can activate malevolent content (a virus or worm). Downloading the message caused no harm -- it's the preview pane that uncorks the content.

Do You Know hOw to maNage oUr pC ? ^_^

If you rarely go online, observe at least basic security precautions and occasionally install new programs, your computer will probably not give you any real trouble.
It's also possible to use your computer very heavily, install and uninstall all sorts of programs, go online extensively, and still avoid real trouble. That is, if you do most of the right things most of the time. (None of us are perfect, eh?)

1. Get serious about online security

How long do you think it takes before an unprotected computer is succesfully attacked? Experiments have shown that it's usually less than 15 minutes (when using a broadband connection).

These days, new PCs come with the Windows Firewall turned on. That's good, but there are many sophisticated attacks that you need to defend against too. You need a comprehensive online defense system to protect your PC over the long term.

2. Get serious about regular backups

Backup is a personal thing. Most of us have "stuff on our computer" that we'd hate to lose -- photos, correspondence, family trees, business records -- things like that. Many of us also invest considerable effort getting our computers set up just the way we like them. We'd hate to lose all that work too. Your backup strategy should depend on what you have at risk and what you're willing to lose.

Backup is insurance. Yes, it costs something -- time, effort and perhaps a little money to get the insurance. It also takes discipline, but backup is the only way to make sure you won't lose the things that are most important to you. The question is not if something will go wrong, but when will it go wrong. Backup can be insurance against little mistakes, and against disaster.

First, do some analysis to decide what you want to back up. Then put the right process and tools in place so that you can do it effectively.

3. At least get interested in housekeeping

The performance of your PC will gradually decline, or it can even become inoperable without some basic maintenance. There's also some basic cleanup you can do that even a new computer can benefit from.
After that general pruning, there are five things -- eliminate spyware, delete unused files, scan your hard drive for errors, defragment your hard drive, and some physical housekeeping -- that you should do once in a while to keep your computer healthy.