what is inside your computer

What's inside your PC?

Warning! Don't open up your PC unless you really know what you're doing. There are dangerous voltages inside, especially near the power supply unit, and some components can remain live for quite a time after the power has been turned off.

Photo: Inside the case of a typical PC showing four key areas of components, described below. Photo by ArmadniGeneral courtesy of Wikimedia Commons, published under a Creative Commons License.
It all looks pretty scary and confusing inside a typical PC: circuit boards like little "cities" with the chips for buildings, rainbow tangles of wires running between them, and goodness knows what else. But work through the components slowly and logically and it all starts to make sense. Most of what you can see divides into four broad areas, which I've outlined in green, blue, red, and orange on this photo.

Power supply (green)

Based on a transformer, this converts your domestic or office power voltage (say 230/120 volts AC) into the much lower DC voltage that electronic components need (a typical hard drive might need just 5–12V). There's usually a large cooling fan on the outside of the computer case near the power socket (or a much smaller fan on a laptop, usually on one side). In this machine, there are two external fans (colored green and blue) just to the left, cooling both the power supply and the mainboard.

Mainboard (blue)

As its name suggests, this is the brain of a computer—where the real work gets done. The main processor (central processing unit) is easy to spot because there's typically a large fan sitting right on top of it to cool it down. In this photo, the processor is directly underneath the black fan with the red central spindle. Exactly what's on the mainboard varies from machine to machine. As well as the processor, there's the BIOS, memory chips, expansion slots for extra memory, flexible ribbon connections to the other circuit boards, IDE (Integrated Drive Electronics) connections to the hard drives and CD/DVD drives, and serial or parallel connections to things like the USB ports, and other ports on the computer case (often soldered onto the mainboard, especially in a laptop).

Other circuit boards (red)

Although the mainboard can (theoretically) contain all the chips a computer needs, it's quite common for PCs to have three other separate circuit boards: one to manage networking, one to process graphics, and one to deal with sound.

• The networking card (also called a Network Interface Card/Controller, NIC, or network adapter), as its name suggests, connects your computer to other machines (or things like printers) in a computer network (typically either a local area network, LAN, in a home or office or the wider Internet) using a system called Ethernet. Older computers may have a separate wireless (WLAN) card for linking to Wi-Fi; newer ones tend to have a single networking card that handles both Ethernet and Wi-Fi. Some computers have chips that do all their networking on the motherboard.
• The graphics card (also called the video card or display adapter) is the part of a computer that handles everything to do with the display. Why isn't that done by the central processing unit? In some machines, it can be, but that tends to slows down both the main processing of the machine and the graphics. Self-contained graphics cards date from the very first IBM PC, which had a standalone display adapter way back in 1981; powerful, modern-style graphics cards for 3D, high-resolution, full-color gaming rolled out from the mid-1990s, pioneered by companies such as Nvidia and ATI.
• The sound card is another self-contained circuit board based around digital-to-analog and analog-to-digital converters: it turns the digital (numeric) information the central processing unit deals with into analog (constantly varying) signals that can power loudspeakers; and converts the analog signals coming in from a microphone into digital signals the CPU can understand. As with networking and graphics, sound cards or sound chips can be integrated into the motherboard.

Drives (orange)

PCs typically have one, two, or three hard drives plus a CD/DVD reader/writer. Although some machines have only one hard drive and a single combined CD/DVD drive, most have a couple of empty expansion slots for extra drives.
PC makers tend to design and build their own motherboards, but most of the components they use are off-the-shelf and modular. So, for example, your Lenovo PC or Asus laptop might have a Toshiba hard drive, an Nvidia graphics card, a Realtek sound card, and so on. Even on the motherboard, the components may be modular and plug-and-play: "Intel Inside" means you've got an Intel processor sitting under the fan. All this means it's very easy to replace or upgrade the parts of a PC either when they wear out or grow obsolete; you don't have to throw the whole machine out. If you're interested in tinkering, there are a couple of good books listed in the "How computers work" section below that will walk you through the process.

External connectors ("ports")

You can connect your computer to peripherals (external gadgets like inkjet printers, webcams, and flash memory sticks) either with a wired connection (a serial or parallel cable) or with wireless (typically Bluetooth or Wi-Fi). Years ago, computers and peripherals used a mind-boggling collection of different connectors for linking to one another. These days, virtually all PCs use a standard way of connecting together called USB (universal serial bus). USB is meant to be "plug and play": whatever you plug into your computer works more or less out of the box, though you might have to wait while your machine downloads a driver (an extra piece of software that tells it how to use that particular piece of hardware).

Photo: USB ports on computers are very robust, but they do break from time to time, especially after years of use. If you have a laptop with a PCMCIA slot, you can simply slide in a USB adapter card like this to create two brand new USB ports (or to add two more ports if you're running short).
Apart from making it easy to swap data, USB also provides power to things like external hard drives. The two outer pins of a USB plug are +5 volt and ground power connectors, while the inner pins carry the data. When you plug your phone into a USB port on a bus or a train, you're just using the outer pins to charge the battery.
USB gives you much more connectivity than old-fashioned serial computer ports. It's designed so you can connect it in many different ways, either with one peripheral plugged into each of your USB sockets or using USB hubs (where one USB plug gives you access to a whole series of USB sockets, which can themselves have more hubs and sockets plugged into them). In theory, you can have 127 different USB devices attached to one computer.

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what is network topologies explain its types,explain star topology,ring topology,bus topology, mesh topology, hybrid mesh topology

Network topology and its types:

Definition 1:

The physical arrangement of connected devices in a network is called network topology;

Definition 1:

The way in which computer and other devices are connected is called network topology.

Types of network topology:

·        Star topology

·        Ring topology

·        Bus topology

·        Mesh topology

·        Hybrid topology

Star topology:

In the computer networking world the most common used topology in LAN is the star topology.

All the computer in star topology are connected to central devices like hub, switch or router using the twisted pair cables.

In star topology, the sending computer sends the data to hub. the hub sends data to receiving computer. Each computer in star network communicates with a central hub.

Star topology can be implemented in home, offices, or even in a building .

Advantages of star topology:

·        It is easy to install and maintain the network.

·        Adding or removing computers can be done without disturbing the network.

·        Easy to detect faults.

·        Failure of computer or link does not effect the whole network.

Disadvantages of star topology:

·        Failure of central hub suffers the entire network.

·        It requires large number of cables to connect computers.

·        It is more expensive.

Ring topology:

Each computer is connected to the next computer while the last one is connected to the first one and making ring.

Messages that are transmitted travel around the ring until they reach the destination computer.

In ring topology,  every computer is connected to next computer .each computer receives message from the previous computer and transmits it to the next computer. the message flows in one direction.

Advantages of ring topology:

·        It is less expensive than star topology.

·        Every computer has equal access to the network.

·        Perform better than a star network under heavy network load.

·        There is no need of server to control the connectivity between computers.

Disadvantages of ring topology:

·        Failure of one node brings the whole network down

·        Error detection and network administration becomes difficult.

·        Moves, adds and changes of devices can effects the network

·        Network is highly dependent on wire which connects different devices.

Bus topology:

Bus topology is that in which all the nodes (computer as well as servers) are connect to the single cable(called bus).

This central cable is the backbone of the network and is known as bus.

Every workstation communicates with the other devices through this BUS. signal from the source is broadcasted and it travels to all workstations connected to bus cable. although the message is broadcasted but only the intended recipient ,whose MAC address or IP  address matches. accepts it. if the MAC/IP address of machine doesn’t matches with the intended address, machine discards the signal.

A collision can occur in bus topology if two computer transmit data at the same time .

Advantages of BUS topology:

·        It is very easy and simple to use.

·        It requires short amount of cables

·        More computer can easily be connected without disturbing the network .

·        If one node fails, it does not effect the whole network.

Disadvantages of bus topology:

·        Entire network goes down if main cable fails.

·        Difficult to detect problem if the entire network shuts down.

·        Not suitable for network with heavy load.

Mesh topology:

Mesh means net in this topology, every computer is directly connected to every other computer ,multiple links exist among network computers, in mesh network message sent can take any of server possible paths form sources to destination this topology is very expensive as it requires more connection mesh network is come only used in very less networks

Advantages of mesh topology:

·        Due to multiple links mesh network can work very fine even under heavy load.

·        Troubleshooting of mesh network is easy as compare to other network.

·        On this network it is easy to add new computer without disturbing other computer

·      Disadvantages  of mesh top0logy:

·        Cable cost is too high due to multiple links

·        It is very difficult to maintain this network due to large number of computer

Hybrid mesh:

In hybrid mesh total links are less than in (n-1)/2 for ”n” computers each computer is not directly connected with each other computer in the network, if for example the total number of computers “n” is 6 in 3 or 9 links instead of 15 then such a network will be a hybrid mesh.

Advantages:

·        Mesh network has high fault tolerance due to multiple links

·        Due to multiple links mesh network can work fine even under severe loads

·        Troubleshooting of mesh network is easy as compared to other network.

Disadvantages:

·        Cable cost is too high due to multiple links this cable cost may even be more than a star network in case of true mesh network among a large number of computers.

·        It is also very difficult to maintain a true mesh for a large number of computers

explain client server, peer to peer and hybrid networking models

Networking models:

Operating system or data communication software that makes the network client server or peer to peer network is called network models.

There are three network models:

·        Client-server model.

·        Peer-to-peer model.

·        Hybrid network model.

Client server model:

ü In a client server arrangement network services are located on the central  computer called a server.

ü The typical LAN is a client server network.

ü The server is the main computer to control the all entire network.

ü The server responds to the request of clients for file, print and other services.

ü The desktop computer function as client and one or special software function as servers.

ü In this model the network administrator  controls the server where as the clients computers are used by users.

ü Each user has its own rights which are allowed by administrator.

ü Window NT window 2000, UNIX & LINUX are used in these models.

ü It is the most secure and safe model for the protection of data and information.

Peer-to-peer model.

ü In this network model the networked computers act as equal partners or peers.

ü As peer each computer can act as a client or server.

ü In this model all computers working are equal.

ü At one time computer A may make a request for a file from computer B which then provides the file to computer A. in this case computer A function as client, while B function as the server.

ü At later time computer A and B can reverse the rules.

ü Window 95,window 98 are used in peer-to-peer network as a operating system.

ü In this model no network administrator is required .

ü As in this network there is no central computer so this model is less secure.

Hybrid network model:

ü The word hybrid means mixture of two opposite qualities in one and same thing.

ü Now when both the client server and peer to peer networking feature exist in a network then such a network will be called hybrid model.

ü The advantages of client server model cancel the disadvantages of peer to peer network whereas the advantages of peer to peer may cancel the disadvantages of client server model.

ü The only disadvantage is that network administrator whose services are still required due to the presence of client server characteristics.

what is cache memory explain its three levels

Cache memory:

It is very fast memory located in between processor and RAM. The CPU uses cache memory to store instruction and data that are repeatedly required to run programs, improving overall system speed .when an information is required by the processor, first it will look up in cache memory, and if it is not available in the cache then it will fetch if from the RAM.

Purpose of cache memory:

The main purpose of cache memory is to eliminate the speed difference between processor register and main memory.

Levels of cache memory:

·        L1 (level 1 cache)

·        L2 (level 2 cache)

·         L3 (level 3 cache)

L1 cache:

L1 cache is built into the actual processor core. A processor core is a processing unit which read instruction to perform specific actions.

It is a part of high speed memory which operate at high speed as CPU. It is very expensive and can store very limited data i.e., 8 to 128 kbytes . it holds data that processor needs to execute instructions.

L2 cache:

L2 cache pulls information from RAM , which is then accessed by the l1 cache. It is bigger in size and slow er in speed then l1 cache. it can store up to 16 mb data and instruction.

The basic purpose of l2 cache is to regularly read somewhat large quantities of data from RAM which is then available in l1 cache.

L3 cache:

L3 cache is a specialized memory that worked hand in hand with l1 and l2 cache to improve computer performance. It is  the largest cache and faster than ram but slower than l1 and  l2 cache.l3 cache has typically been built into the motherboard while l1 an l2 cache are built into processor .processor firs look for instruction  in l1 cache, and then it checks l2 and l3 cache respectively.