Computer Modems

Modems

A modem converts a computer's digital signals into the telephone's analog signals. The word modem comes from the two steps in this process: "Modulation" and "Demodulation". Digital data from a computer is fed to a modem which converts data into an analog signal. Another modem converts these signals back into the original digital signal. Data can transmit at the rate of several thousand bits per second over ordinary telephone lines and at even higher rates over "shielded" lines. Modems operate in full or half duplex mode, depending on whether they send data together or one at a time. Below are articles on computer modems, communication hardware and modem reviews.

What is the Function of a Modem

A device, which carries out the two important tasks of modulating and demodulating the analog signals is called a modem. In this article, you will learn what is the function of a modem.

Modulation is the process of changing the form of the signal carrying the information. The demodulation process does the task of extracting information from the signals that are modulated. Analog signals can encode the digital information at the time of modulation and decode it back during demodulation to transmit the data, using devices such as a radio or a diode. Modems are classified on the basis of two criteria,

Data sent per unit time
Change in the state of the signal per unit time

They were first used in the '60s decade, for connecting computers over a network of telephone lines. The period is also known as the age of time-share computers, since the computers had to buy time in order to connect to the network by means of a modem, which had a speed of 300 bits/second. To know what is the function of a modem, read the paragraphs below.

Working Mechanism

A computer sends information in the form of digital signals. But the information over the telephone lines needs to be transmitted in the form of analog signals. To solve this problem, the modem converts the digital signals into analog signals. These analog signals are carried over the telephone lines. When these signals reach another computer, the analog signals are converted back to the digital form.

Function

In addition to converting digital signals into analog signals, the modems carry out many other tasks. They minimize the errors that occur while the transmission of signals. They also have the functionality of compressing the data sent via signals. They also do the task of regulating the information sent over a network.

Error Correction: In this process the device checks if the information they receive is undamaged. It divides the information into packets called frames. Before sending this information, it tags each of the frames with checksums. Checksum is a method of checking redundancy in the data present on the computer. The device that receives the information, verifies if the information matches with checksums, sent by the error-correcting modem. If it fails to match with the checksum, the information is sent back.
Compressing the Data: For compressing the data, it is sent together in many bits. The bits are grouped together by the device in order to compress them.
Flow Control: Different devices vary in their speed of sending signals. Thus, it creates problems in receiving the signals if either one of them is slow. In the flow control mechanism, the slower one signals the faster one to pause, by sending a 'character'. When it is ready to catch up with the faster one, a different character is sent, which in turn resumes the flow of signals.

Different Types

Modems are classified on the basis of different criteria such as the place where they are installed, the manner in which they accept information, and the way they transmit signals. Based on these criteria, they are divided into the following types.

Internal and External: The former is in the form of circuit boards, fitted in expansion slots of the motherboard. The latter is enclosed in a separate case, and not inside the system units. It is connected to the computer and the telephone line by means of two separate cables.
Intelligent and Standard: The former accepts instructions entered from the keyboard of a microcomputer. The latter responds to commands and transmits information simultaneously. It is done with the help of microprocessor chips.
Wireless and Short-Haul: The former transfers data by means of cables. Since they don't need an external power source, they are also called 'modern eliminators'. The latter does not require any kind of cable to transmit the data signals.

Modems have an important role to play in computer networking. Broadband USB ones have proven useful for laptops. With improvement in technology, they are becoming advanced and refined in their working. Facilities like satellite internet are provided by the means of satellite modems. In this age of information technology, the use of high speed internet access like the broadband is bound to grow.

Component/configuration of Computer Part-3

MOTHER BOARD/MAIN BOARD

Computer motherboards are the circuit boards that contain the essential components of the computer like RAM, ROM, hard disc and so on. A PC cannot work without the motherboard.

Computer Motherboard Types

The motherboard is the soul of your computer. This is where the most important entity, your computer's processor, is embedded. All computer peripherals ultimately connect to the motherboard. Scroll below to learn which are the different types of computer motherboards.

A computer motherboard is nothing but the circuit board or the circuit which controls the entire functioning of the computer. All the components that make up your computer are connected to the motherboard. The computer processor, which is the most important component of your computer, is mounted on the motherboard. All other components like the keyboard, monitor, mouse, hard drives, etc., are all connected to the motherboard through cables.

Why is it important to know the different computer motherboard types? Well, if you are planning to assemble a desktop computer, then this is the most important question that needs to be answered. Computer processors are motherboard specific and so are the computer cabinets. So it is very important that you know the different types of motherboards before you start with the assembly process.

Types of Computer Motherboards

There are different ways to classify motherboards, which are:

Classification Based on Assembly

Integrated Processors

Video, graphics, sound... such facilities involve components. Peripheral device slots, serial parallel ports and input output ports are other physical components or parts that are involved in the working of a computer. When such components are provided for by the motherboard, i.e. they are built into the motherboard, the motherboard is called integrated.

For example, to make a computer capable of connecting to networks, a network card is integrated onto the motherboard itself. So you do not need to buy a network card. This sort of motherboard allows for better air flow within the computer's case. Integrated motherboards cost less to make but their downside is that, if even one component on the motherboard fails, the entire board might have to be replaced. Repairing or replacing this sort of motherboard, is expensive.

Non-integrated Processors

With non-integrated motherboards, electronic components and parts are fitted individually and as needed. Input output ports, connectors, RAM etc. are fixed to the motherboard using expansion slots. So you can add one or more components as needed. This allows for greater customization and freedom in designing a PC. Gamers, for example, could fix a high-end graphics card of their choice, using the expansion slot, instead of settling for an average video card on an integrated motherboard.

But customizing a motherboard can get expensive and this is the problem with non-integrated motherboards; the initial cost is high as components need to be bought and fixed. Plus, there should be enough expansion slots to accommodate the multiple components. However, if a single component fails, then only it has to be replaced or repaired, which is a cheaper operation as opposed to replacing the entire motherboard.

Classification Based on Processor

This way of differentiating computer motherboards is based on motherboard socket types. The CPUs that are available in the current market, are compatible only with specific motherboards.

Socket A Motherboards

These motherboards are meant for AMD and Durons processors. The Socket A motherboard is also known as Socket 464 motherboard. The CPU socket in the motherboard has 462 pins and it comes in a PGA (Pin Grid Array) packaging. The bus speed of this type of motherboard is 100 to 200 MHz.

Socket 370 Motherboards

Meant for Intel Pentium III and Celeron processor, this motherboard comes for CPUs with 370 pins. It can also support VIA Cyrix III and VIA C3 processors. The bus speed for this type of motherboard is 66 to 133 MHz and it also comes in a PGA package.

Socket 378 Motherboards

This is meant for Pentium 4 processors. It also comes in a PGA package and has 478 pins. The bus speed is 100 to 200 MHz. This motherboard can also support Intel Pentium 4EE and Intel Pentium M processor. This type of motherboard is also known as Socket N motherboard.

Socket T Motherboards

Also known as LGA 775, this motherboard is meant for Intel Core 2 Duo, Intel Core 2 Quad and Intel Xeon processor. Of course, this motherboard can also support other Intel processors such as Celeron, Pentium 4, Pentium D, Celeron D and Pentium XE processor. Its specifications include 775 pins and a very high bus speed of 1600 MHz. It also comes in a PGA package.

Socket 939 Motherboards

The Socket 939 is meant mainly for the AMD family. It can support AMD processors like the Athlon 64, Athlon 64 FX, Athlon 64 X2 and Opetron. It has 939 pins and can have a bus speed from 200 to 1000 MHz. Just like the types described above, it also comes in a PGA package.

Socket AM3 Motherboards

Socket AM3 is among the most recently developed motherboards. Introduced in 2009, this motherboard is meant for AMD Phenom II and AMD Athlon II processors. It has 941 pins and a bus speed range of 200 to 3200 MHz. The packaging for Socket AM3 motherboard is PGA.

Socket H Motherboards

The Socket H or LGA 1156 is meant for Intel Core i3, Intel Core i5 and Intel Core i7processors. It has 1156 pins and comes in LGA (Large Grid Array) packaging.

Classification Based on Dimension

The dimensions of a motherboard, also known as the form factor, is another way of distinguishing between different motherboard types.

ATX Motherboards

The ATX (Advanced Technology Extended) motherboard has a length of 12 inches and a width of 7.5 inches. The I/O ports and USB ports meant for the motherboard are integrated directly in it. The bus speed in ATX motherboard is 100 MHz. This board is mainly meant for Intel processors.

Full AT Motherboards

This was the first type of motherboard, which was 12 inches wide and 11 inches long. This motherboard suffered from a lot of problems, like cumbersome access to components and overheating.

Baby AT Motherboards

With a dimension of 10 by 8.5 inches, this motherboard is meant for classic Pentium processors. The DIN keyboard connector at the top right corner of this motherboard, makes recognizing this motherboard a relatively simple task.

How to Determine a Motherboard Type?

Normally, the documentation that accompanies the motherboard, is the best way for determining your computer's motherboard. If in case you do not have access to those documents, you can go to the System Devices tab located in the Device Manager and try to find your motherboard type. You can also run msinfo32 to find information about the installed hardware. There are various other third party programs too, which you can use for determining the motherboard. You can also simply open the cabinet of your CPU and look for a label on the computer's motherboard. It is usually present in the upper left or right corner of the motherboard. Another way of finding out the motherboard is, if you can locate the FCC (Federal Communications Commissions) identification number of the motherboard and perform a search on the type of motherboard using the same.

The type of motherboard used for your computer is also used for determining various other factors. For example, DDR SDRAM is the fastest of all the different types of RAM and only Socket A motherboards can be used for the same. Similarly, SDRAM is compatible with Socket 370 and RD RAM with socket 478. Similarly, the type of motherboard determines various other factors too.

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Computer Memory

COMPUTER MEMORY

Computer memory is a physical electronic device that is used to store applications and data, temporarily or permanently, as required by a computer and/or its user. Here is more on the different types of computer memory...

TYPES OF COMPUTER MEMORY

1. Primary Memory

i)   RAM

ii)  ROM

2. Secondary Memory

i)    Punching Devices
ii)   Magnetic Tape
iii)  Floppy Disk
iv)  Optical Discs (CD/DVD)
v)   Hard Disk Drives
vi)  Flash Drives

1. PRIMARY MEMORY

Primary Memory (also called main memory), is used for immediate access of data by the processor. While primary memory storage demonstrates faster processing ability, it is costly and hence is not largely used for data storage. Most computer systems around the world use primary memory only for bootstrapping and related purposes, and use secondary memory devices for personal data storage purpose.

Primary Memory can be divided into two types - Random Access Memory (RAM) and Read Only Memory (ROM). RAM retains its contents as long as the power supply is on. A RAM chip is used as primary memory in most computers today. However, older computers (in the '80s) used ROM devices (floppy disks, magnetic tapes, paper clips or punches; but more prominently floppy disks) as primary memory mechanism.

i)  RAM (RANDOM ACCESS MEMORY)

RAM is a memory scheme within the computer system responsible for storing data on a temporary basis, so that it can be promptly accessed by the processor as and when needed. It is volatile in nature, which means that data will be erased once supply to the storage device is turned off. RAM stores data randomly and the processor accesses these data randomly from the RAM storage. The information stored in the RAM is typically loaded from the computer's hard disk, and includes data related to the operating system and certain applications. When the system is switched off, the RAM loses all stored information. The data remains stored on secondary storage though, and can be retained when the system is running again. Some of the earliest computers used delay-line format of computer storage. Most modern computers use an embedded RAM circuitry on the motherboard which reads data in bursts. So, modern RAM devices are not random memory devices as such; they are burst memory access devices, but the term RAM has stuck in everyday usage.

There are primarily two forms of RAM: Static RAM (SRAM) and Dynamic RAM (DRAM).

Static RAM: The most expensive of the lot, SRAM uses bistable latching circuitry to store one bit each, and hence is faster than its counterpart. Its high price prevents it from being widely used in everyday computing machines, but many modern machines use SRAM as the processor's cache register.

Dynamic RAM: Widely used in modern computers as primary memory, DRAM is slower than SRAM, but is inexpensive due to its one transistor-one capacitor paired assembly of memory storage.

ii)  ROM (READ ONLY MEMORY)

Unlike RAM, ROM is a permanent form of storage. ROM stays active regardless of whether power supply to it is turned on or off. In spite of this, ROM was used (in rare cases is still used) as the primary device for most computers back in the '80s. This was because ROM devices do not allow data stored on them to be modified. As the name itself suggests, data can only be accessed and read by the user, not overwritten, upgraded, or modified. This made it an ideal choice as bootable devices for old computers, programmable interpreters, and portable OS files carrier. The system programs stored on a ROM device could never be altered and hence, stayed secure for use.

The ROM memory used in modern computers is pre-programmed by the circuit manufacturer and cannot be altered by the user. The main reason why ROMs are not widely used in modern computer systems is because of the masking and error-retrieval costs. These processes are very expensive, and virtually negate the inexpensive manufacturing involved.

2. SECONDARY MEMORY

Secondary memory is available on mass storage devices for permanent data storage. Data stored on a secondary device is retained even when it is not supplied any power. This data can be transported in most cases, and looks and appears the same on any machine, irrespective of where the data was first copied onto the secondary storage device.

Unlike primary memory, secondary memory is not directly accessible by the computer. When a computer needs to run or execute an application stored in secondary memory, it first brings it to primary memory storage for a while, to control and carry out its execution. Once execution of the application is done, the processor releases the application and restores its control and memory data with the secondary memory device.

Popular secondary memory devices include hard disk drives, flash drives (pen drives, memory cards etc.), and zip drives. A couple of decades ago, as the 'personal computer' (PC) revolution was gathering storm, especially in America, floppy disks had acquired almost a cult status amongst PC users. Eventually, floppy disks were phased out by a better technology - a contemporary form of the optical drive called the Compact Disc or CD. CDs came with better speed and larger storage alternatives as compared to floppies. DVDs eventually took over the mantle from CDs, courtesy their ability to store almost 4 times more data. Although DVDs are still widely used, the preferred devices of secondary storage nowadays are portable hard disk drives or flash drives.

i)  PUNCH DEVICES

The essential data storage techniques of the '50s and '60s, punch tapes and punch cards have become passé since the advent of newer data storage formats.

Punch Tapes: A 0.1 mm thick paper strip was used to store data in the form of punched holes. A keyboard was used to punch the desired alphabet onto the tape. This alphabet was represented on the tape by a certain number and a select pattern of holes. A separate tape machine was used to send and receive these tapes for distance communication purposes. For computing purposes, stored data on the tapes would be read by the processing unit's inbuilt decoding machine.

Punch Cards: Primarily used in textile and handloom industries, punch cards stored instructions of operation for machines. Early digital computers made punch cards popular as data storage assemblies. Their working is pretty much similar to that of punch tapes, except for the fact that instead of paper strips, this technique uses cards about 3¼ inches × 7⅜ inches in size. Around the 1920s and 1930s, IBM hit upon a series of card innovations which enabled pre-punched data verification cards and cards with the ability to read alphabets, numbers, and signs (symbols) on a single multipurpose card.

ii)  Magnetic Tape

Magnetic tape as a recording technique was invented in 1928. This formed the basis for magnetic digital information storage. This form of data storage gained immense popularity in the '70s, when magnetic tapes were wound around 10.6-inch reels. The device used for the read-write operations on these tapes is called a tape drive. Until the early 1980s, magnetic tape drives were huge external devices. With the introduction of IBM's 3480 family of magnetic tape cartridges, most magnetic tape storage assembly went inside the central processing unit.

Transferring data at around 7,200 characters/second, magnetic tapes store data in sequential order, which also can be accessed only in a sequential order. The magnetic tape's storage density and feasibility offered it a ready-made advantage against punched storage techniques. Even through the '90s, as floppy disks and compact discs were taking over the market, magnetic tapes held a fan-like following among large corporations for large-scale data storage. By the turn of the century, as solid state data storage took over, magnetic tapes lost hold with them too.

iii)  Hard Disk

The hard disk is also called fixed disk. It consists of one or more metal plates that are coated with magnetizable material. The plates of the disk are fixed permanently in the drive. Term hard disk is also called permanent disk and non-volatile disk.

A magnetic disk on which you can store computer data. The term hard is used to distinguish it from a soft, or floppy, disk. Hard disks hold more data and are faster than floppy disks. A hard disk, for example, can store anywhere from 10 to more than 100 gigabytes.
A single hard disk usually consists of several platters. Each platter requires two read/write heads, one for each side. All the read/write heads are attached to a single access arm so that they cannot move independently. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder. For example, a typical 84 megabyte hard disk for a PC might have two platters (four sides) and 1,053 cylinders.

iv)  Floppy Disk

Floppy diskette is also called simple a diskette or a disk. It is a small flexible plastic disk that is coating with magnetizable material. It was invented by IMB in early 1960s. Nowadays, floppy disks are available in the two sizes 5.25 inch diameter disk and 3.5 inch diameter disk.

Floppies come in three basic sizes:
8-inch:The first floppy disk design, invented by IBM in the late 1960s and used in the early 1970s as first a read-only format and then as a read-write format. The typical desktop/laptop computer does not use the 8-inch floppy disk.
5��-inch: The common size for PCs made before 1987 and the predecessor to the 8-inch floppy disk. This type of floppy is generally capable of storing between 100K and 1.2MB (megabytes) of data. The most common sizes are 360K and 1.2MB.
3��-inch: Floppy is something of a misnomer for these disks, as they are encased in a rigid envelope. Despite their small size, microfloppies have a larger storage capacity than their cousins -- from 400K to 1.4MB of data. The most common sizes for PCs are 720K (double-density) and 1.44MB (high-density). Macintosh's support disks of 400K, 800K, and 1.2MB.

 

v)   Optical Drives CD/DVD

Philips and Sony collaborated in the '70s on a project to create a new digital audio disc. This collaboration brought together the optical disc drive technologies both the companies were earlier separately working on. Launched in 1982-83, the Compact Disc (CD) eventually went on from being an audio disc to a data storage device.

computer-memory
The DVD, (originally Digital Video Disc, but later amended to Digital Versatile Disc) format was based on the CD format, and was developed together by Philips, Sony, Toshiba, and Panasonic around the early '90s. It was launched in 1995 and became an instant success by the virtue of being same size as a CD yet offering almost 4 times its memory space. While data storage isn't forfended, DVDs are mostly used for audio and video recording/storage/playback purposes.

In the late '90s, the popularity of CDs took a major three-way hit. While the launch of DVD had already put it out of favor with video enthusiasts, its audio and data storage purposes also waned in lieu of advancing technology. Affordable portable hard disk drives and flash drives drove CDs out as a preferred form of data storage. On the other hand, the easy availability of MP3 players and the legendary rise of Apple's iPod, practically drove audio CDs out of the market. The DVD too has found successors in the form of HD DVD and Blu-ray discs, and is in the gradual process of being phased out from regular use.

 

 vi)  Flash Drives

A flash drive is a data storage device that uses flash memory for storage purposes. Typical in design, flash drives are light-weight and small in design; and are hence easily portable. Flash drives operate from the power supplied by a computer's USB port (the port in which they are plugged in). The data on it can be erased and re-programmed as per the user's requirements. It only has a specific number of erase and write cycles that it can withstand, after which it creates a tendency to lose out on the stored information. Memory cards and USB flash drives are some modes of this type of memory storage. Low cost, minimal power consumption, and portable features make flash drives extremely desirable and popular in modern times.

The concept of computer memory has evolved since the first electronic computer (ENIAC) was set up in 1946 with a primitive read only pre-stored programming mechanism. ENIAC used function tables for storing instructions. Its maximum storage capacity was 600 two-hundred digit decimal instructions. The way data is stored today and the volumes in which it can be stored today is like a million miles ahead of that.

Memory management has become an important concept in every computer programmer's textbook. Corporations and computer scientists keep researching for newer, simpler, easier, and cost-effective methods of memory storage that can hold larger and larger capacity of data than what is currently possible. Computer memory and its evolution is a constant process, much like the rest of technology. It has changed multifold over the last few decades; expect it to change multifold in the decades to come.

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Component of computer Part-2

Component/configuration of computer

Central Processing Unit/CPU

Central Processing Unit (CPU) is the main part of the computer system. It control various components of computer system and perform all operations on data according to programe instructions.

CPU consist of two parts

i)   Control Unit/CU
ii)   Arithmetic & Logical Unit/ALU

Control Unit/CU

i)  Control Unit control the functions of computer. It controls input output device functions and complete all process.

Arithmetic & Logical Unit/ALU

ii) All mathematical calculation (+, -, /, X) can make comparisons like less then (<) greater then (>) and equal (=) etc.

CD-ROM

CD-ROM stand for Compact Disk Read Only Memory. The data on a CD-ROM can only be read cannot be delete or change and write.

       It is the most commonly used type of optical storage. It has the storage capacity of up to 650MB. It is used for storing large amounts of data and application program.

DVD-ROM

DVD-ROM stand for Digital Video Disk Read Only Memory. The working of DVD is similar to that of the CD-ROM. A DVD uses laser and its storage capacity is seven times than CD-ROM. DVD can store up to 4GB of data.

CD/DVD Burner/ Writer

It write on CD/DVD
There are two types discs
          i)  Writable Disk
         ii)  Re-Writable Disk

 Watch video to see how do CDS work?

Component of computer Part-1

Component/Configuration of computer

Mouse

Mouse is an input device. It is used to control movement of a pointer on the screen. It has two or three button on its top and a ball inside is body.

            Mouse is mainly used in graphic application. It is play games on the computer. The mouse is a required input device in all versions of Ms Windows. The latest mouse devices have more useful technology. Laser and wireless technology.

Types of Mouse

i)   PS2 Mouse

ii)  Serial Mouse

iii) USB Mouse (USB Stand for Universal Serial Bus)

Keyboard

          Keyboard is the most commonly used input device. It is used to enter data and program instructions into the computer.

          The keyboard like a typewriter with alphabetic characters A to Z and numeric key digits 0 to 9 and many other keys with special functions.

Types of Keyboard

i)   PS2 Keyboard

ii)  USB Keyboard

Monitor

          Monitor show all work and results on the screen from the computer. It also called (VDU) VDU stand for Visual display Unit.

           The monitor/VDU is the most commonly used output device and look like a TV screen.

 Types of computer's Monitor

 i)   CRT Monitor  (CRT stand for Cathode Ray Tube)

ii)   LCD Monitor  (LCD stand for Liquid Crystal Display)

CRT Monitor

LCD Monitor

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Types of Computer

Different types of computer

Micro/Personal Computer

This is smallest computer in size. Its speed is slowest. It is a single user. It use in Homes, Offices, Banks, Market etc. It is cheapest in cost. 

Mini Computer

These are larger in size then micro/personal computer. but smaller then main frame computer. Its speed is faster then micro/personal computer. It is multiuser computers. It is costly in price and using in business, Banks, Large markets and etc.

Mainframe Computer

There are larger in size then mini computer. its speed is faster then mini computer. It is costly in price and produced much heat. it is use in large organization, stock exchange and etc.

Super Computer

These are larger in size then all computers types. then are the fastest in speed. They also produced much heat and most expensive computer in cost.

        They are use in weather for casting, economic for costing and weapon designing and etc.

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Input & Output Devices

Input Devices

The devices that are used to enter data and instructions into the computer system are called input devices. For e.g

        Keyboard, Mouse, Digital Scanner, Camera etc.

Output Devices

These devices that are used to receive data and instructions from the computer system are called output devices output devices for e.g.

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