Computer Compenents

Computer Components

Computers come in all types and sizes. There are primarily two main sizes of computers. They are:

• Portable
• Desktop

The portable computer comes in various sizes and are referred to as laptops, notebooks, and hand-held computers. These generally denote different sizes, the laptop being the largest, and the hand-held is the smallest size. This document will mainly talk about the desktop computer although portable computer issues are also discussed in various areas.

Computer Components:

Computers are made of the following basic components:

1. Case with hardware inside:
   
   
   1. Power Supply - The power supply comes with the case, but this component is mentioned separately since there are various types of power supplies. The one you should get depends on the requirements of your system. This will be discussed in more detail later
      
   2. Motherboard - This is where the core components of your computer reside which are listed below. Also the support cards for video, sound, networking and more are mounted into this board.
      
      
      1. Microprocessor - This is the brain of your computer. It performs commands and instructions and controls the operation of the computer.
      2. Memory - The RAM in your system is mounted on the motherboard. This is memory that must be powered on to retain its contents.
      3. Drive controllers - The drive controllers control the interface of your system to your hard drives. The controllers let your hard drives work by controlling their operation. On most systems, they are included on the motherboard, however you may add additional controllers for faster or other types of drives.
   3. Hard disk drive(s) - This is where your files are permanently stored on your computer. Also, normally, your operating system is installed here.
      
   4. CD-ROM drive(s) - This is normally a read only drive where files are permanently stored. There are now read/write CD-ROM drives that use special software to allow users to read from and write to these drives.
      
   5. Floppy drive(s) - A floppy is a small disk storage device that today typically has about 1.4 Megabytes of memory capacity.
      
   6. Other possible file storage devices include DVD devices, Tape backup devices, and some others.
2. Monitor - This device which operates like a TV set lets the user see how the computer is responding to their commands.
   
3. Keyboard - This is where the user enters text commands into the computer.
   
4. Mouse - A point and click interface for entering commands which works well in graphical environments.

These various parts will be discussed in the following sections.

Computer Of Classification

Types of Computers
1. Analog Computers

Analog computers are used to process continuous data. Analog computers represent variables by physical quantities. Thus any computer which solve problem by translating physical conditions such as flow, temperature, pressure, angular position or voltage into related mechanical or electrical related circuits as an analog for the physical phenomenon being investigated in general it is a computer which uses an analog quantity and produces analog values as output. Thus an analog computer measures continuously. Analog computers are very much speedy. They produce their results very fast. But their results are approximately correct. All the analog computers are special purpose computers.
2. Digital Computers

Digital computer represents physical quantities with the help of digits or numbers. These numbers are used to perform Arithmetic calculations and also make logical decision to reach a conclusion, depending on, the data they receive from the user.
3. Hybrid Computers

Various specifically designed computers are with both digital and analog characteristics combining the advantages of analog and digital computers when working as a system. Hybrid computers are being used extensively in process control system where it is necessary to have a close representation with the physical world.

The hybrid system provides the good precision that can be attained with analog computers and the greater control that is possible with digital computers, plus the ability to accept the input data in either form.

Classification of Computers According to Size
1. Super Computers

Large scientific and research laboratories as well as the government organizations have extra ordinary demand for processing data which required tremendous processing speed, memory and other services which may not be provided with any other category to meet their needs. Therefore very large computers used are called Super Computers. These computers are extremely expensive and the speed is measured in billions of instructions per seconds.
2. Main Frame Computers

The most expensive, largest and the most quickest or speedy computer are called mainframe computers. These computers are used in large companies, factories, organizations etc. the mainframe computers are the most expensive computers, they cost more than 20 million rupees. In this computers 150 users are able to work on one C.P.U. The mainframes are able to process 1 to 8 bits at a time. They have several hundreds of megabytes of primary storage and operate at a speed measured in nano second.
3. Mini Computers

Mini computers are smaller than mainframes, both in size and other facilities such as speed, storage capacity and other services. They are versatile that they can be fitted where ever they are needed. Their speeds are rated between one and fifty million instructions per second (MIPS). They have primary storage in hundred to three hundred megabytes range with direct access storage device.
4. Micro Computers

These are the smallest range of computers. They were introduced in the early 70’s having less storing space and processing speed. Micro computers of todays are equivalent to the mini computers of yesterday in terms of performing and processing. They are also called “computer of a chip” because its entire circuitry is contained in one tiny chip. The micro computers have a wide range of applications including uses as portable computer that can be plugged into any wall.
5. Laptop Computers

The smallest computer in size has been developed. This type of small computers look like an office brief case and called "LAPTOP" computer. The laptops are also termed as "PORTABLE COMPUTERS." Due to the small size and light weight, they become popular among the computer users. The businessmen found laptop very useful, during traveling and when they are far away frm their desktop computers. A typical laptop computer has all the facilities available in microcomputer. The smallest laptops are called "PALMTOP".

Read more: Classification of Computers | Types of Computer http://www.friendsmania.in/forum/showthread.php?t=25530#ixzz23b5jOodH

Computer History And Generation

Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices.

The history of computer development is often referred to in reference to the different generations of computing devices. Each of the five generation of computers is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices. Learn about each generation and the developments that led to the current devices that we use today.

Related Webopedia Definitions: computer, magnetic drums, binary, integrated circuit,  semiconductor, nanotechnology

First Generation (1940-1956) Vacuum Tubes

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The first computers used vacuum tubes for circuitry and magnetic drums formemory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.

First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

Second Generation (1956-1963) Transistors

Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.

Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.

The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated Circuits

The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitorsand interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Fourth Generation (1971-Present) Microprocessors

The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip.

In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handhelddevices.

Fifth Generation (Present and Beyond) Artificial Intelligence

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

DID YOU KNOW...?

An integrated circuit (IC) is a small electronic device made out of a semiconductor material. The first integrated circuit was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor.

What Is Computer Network

A computer network is a group of computers connected to each other electronically. This means that the computers can "talk" to each other and that every computer in the network can send information to the others. Usually, this means that the speed of the connection is fast - faster than a normal connection to the Internet. Some basic types of computer networks include:

• A local area network (often called a LAN) connects two or more computers, and may be called a corporate network in an office or business setting.
• An "internetwork", sometimes called a Wide Area Network (because of the widedistance between networks) connects two or more smaller networks together. The largest internetwork is called the Internet.

Computers can be part of several different networks. Networks can also be parts of bigger networks. The local area network in a small business is usually connected to the corporate network of the larger company. Any connected machine at any level of the organization may be able to access the Internet, for example to demonstrate computers in the store, display its catalogue through a web server, or convert received orders into shipping instructions.

Microsoft Windows, Linux and most other operating systems use TCP/IP for networking. Apple Macintosh computers used Appletalk in the past, but it uses TCP/IP now.

To set up a network an appropriate media is required. This can be wired or wireless. Twisted-pair, co-axial or fiber-optic are examples of cable and infra-red, blue-tooth, radio-wave, micro-wave etc. are wireless media used for networking. When you are working with a mere LAN, computers, media and peripherals are sufficient. But when you are working with a wider range you have use some additional devices like bridge, gateway or router to connect different small or large networks. And obviously a protocol must be maintained.

To set up a network you have to select an appropriate topology to arrange the hardware devices using the media. Topologies generally used are bus-topology, ring-topology, star-topology, tree-topology, object-oriented topology etc. Among these star-topology and tree-topology are most popular nowadays.^[source?]

Contents   [hide]  1 Network models and their importance 2 OSI model 2.1 Layer 1 2.1.1 Baseband 2.1.2 Modulated transmission 2.2 Layer 2 2.3 Layer 3 2.3.1 IP address 2.4 Layer 4 2.5 Layers 5-7 3 Networking terms 3.1 Latency 3.2 Capacity (bandwidth) 3.3 Broadcast 4 References

[change]Network models and their importance

Example of communication in network model

The network communication technology as one complet would be very difficult to implement. To simplify it, we must implement various layered network models such as ISO/OSI. All network models are based on the same principle. The upper layer uses services of the lower one and provides services for the upper one. The specific layer can only communicate with the same layer on the destination device.

[change]OSI model

OSI (Open Systems Interconnection) is a 7-layer network model specified by ISO (International Organization for Standardization) norm and is widely used all around the world. The concept of a seven-layer model was provided by the work of Charles Bachman^[1], Honeywell information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN and CYCLADES networks and the work in IFIP WG6.1.

Data unit	Layer	Function
Data	Application	Network process to application
	Presentation	Encryption, decryption and data converting
	Session	Managing sessions between applications
Segments	Transport	End-to-end connection and reliability
Packets (datagrams)	Network	Path determination and logical addressing
Frame	Data link	Physical addressing
Bit	Physical	Signal and binnary transmission

[change]Layer 1

Digital modulation:
16-QAM with example constellation points.

Analog modulation:
FM - frequency
AM - amplitude

The physical layer defines electrical and physical specifications for devices. It also specifies modulated and baseband transmission.

[change]Baseband

Baseband is transmission of digital data in their raw form (1001 1101 1010 0011). This allows very fast and reliable communication over short distances; however, due to the realistic electrical properties of used media, the range of baseband transmission is very limited and decreases with increasing speed. Baseband technology is frequently used on LAN.

• UTP cable – max 100 m on 100 Mb/s speed without repeater
• Optical fiber – max 1 km on 100 Mb/s speed without repeater

Typical technology: Ethernet

[change]Modulated transmission

In telecommunications, modulation is the process of conveying a message signal, for example adigital bit stream or an analog audio signal, inside another signal that can be physically transmitted. The device that provides modulation of the baseband signal is called a modulator, and the device that provides demodulation of the modulated signal back to baseband is called a demodulator. Today, the modulator and demodulator are integrated into one device calledModem (modulator-demodulator). Frequently used on WAN, WLAN, WWAN.
Typical technology: WI-FI, ADSL, cable TV connection (CATV)

[change]Layer 2

The data link layer provides the functional and procedural means to transfer data betweennetwork entities and to detect and possibly correct errors that may occur in the physical layer.

[change]Layer 3

The network layer provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network using the IP address.

[change]IP address

An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. At present there are two versions of protocols in use – IPv4 andIPv6.

• IPv4 uses 32-bit addressing which limits address space up to 4294967296 (2³²) possible unique addresses.

Example: IP-192.168.0.1 mask-255.255.255.0 means that the network address is 192.168.0.0 and the device address is 192.168.0.1

• IPv6 uses 128-bit addressing which limits address space up to 2¹²⁸ possible addresses. It is deemed sufficient for the foreseeable future. Full IPv6 support is still in the implementation phase.

[change]Layer 4

The transport layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI.

• TCP (transmission control protocol) provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer. TCP is used for applications that strictly require reliable transfer (e-mail, WWW, file transfer (FTP), ...)
• UDP (user datagram protocol) uses a simple transmission model without implicit handshaking dialogues for providing reliability, ordering, or data integrity. UDP is used in applications where we require reduced latency over reliability (stream videos, VOIP, online games,...)

[change]Layers 5-7

Commonly united into one layer in simplified network models, its main purpose is to interact with applications, encrypting and establishing dedicated connections if necessary.

[change]Networking terms

[change]Latency

Latency, incorrectly called ping, is a value that measures how much time packets need to travel to their destination. It is measured in miliseconds (ms). The tool that measures latency is called ping, commonly using special ICMP packets which are smaller than standard data packets so they do not weight the network by their presence.

• Immediate latency is measured every X seconds and immediately displayed. Its value constantly changes due to the natural properties of packet-switching network technology. High latency peaks have negative effects on most network applications which can adapt to average latency by allocating corresponding size of memory as buffer. High latency peaks lead to emptying of this buffer and to temporary freezing of applications. This freezing is commonly called lag.
• Average latency is the sum of immediate latency measured Y times every X seconds divided by Y. Average latency is used to estimate size of the buffer, mainly because it does not change so often. Buffer enables some applications such as stream videos to run smoothly even with high average latency, but it cannot protect us from high latency peaks.

ADSL frequency plan.
Upstream + downstream = network bandwidth

[change]Capacity (bandwidth)

Capacity is a measure of transfer capacity of a network and is measured in bits per second (bps or b/s), today commonly Mbps or Mb/s. It shows us how many data units are transferred each second. At present, the average bandwidth is far higher than is necessary and it is not a limiting factor in most cases.

• Uplink is how much bandwidth is used for transferring data from user to server (usually lower for end users).
• Downlink is how much bandwidth is used for transferring data from server to user (usually higher for end users).

[change]Broadcast

Broadcast is a special transmission that is not addressed to a single device but to all devices in specific network. It is mostly used to automatically issue IP addresses to devices by a DHCP server and to create an ARP table that maps the network and speeds up the traffic.

[change]References

1. ↑ [1] at www.computerhistory.org.