Read Only Memory. What are the types of ROM

Read Only Memory (ROM) is an example of nonvolatile memory.  ROM is a class of storage medium used in computers and other electronic devices. Read Only Memory (ROM), also known as firmware, is an integrated circuit programmed with specific data when it is manufactured. The instructions for starting the computer are housed on Read only memory chip.

ROM chips are used not only in computers, but in most other electronic items as well. Because data is fully incorporated at the ROM chip's manufacture, data stored can neither be erased nor replaced. This means permanent and secure data storage. However, if a mistake is made in manufacture, a ROM chip becomes unusable. The most expensive stage of ROM manufacture, therefore, is creating the template.

If a template is readily available, duplicating the ROM chip is very easy and affordable. A ROM chip is also non volatile so data stored in it is not lost when power is turned off. ROM is a  semiconductor memory that is capable of operating at electronics speed.

                                                             ROM Types : 

 PROM : Short for programmable read-only memory, a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROMs retain their contents when the computer is turned off. The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.

EPROM : Acronym for erasable programmable read-only memory, and pronounced ee-prom, EPROM is a special type of memory that retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. To write to and erase an EPROM, you need a special device called a PROM programmer or PROM burner.

EEPROM : Short form of electrically erasable programmable read-only memory. EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM.

Chapter : Memory & Input/Output Unit
• Computer Fundamental 

How can you classify Storage Devices? What are its different types elaborate?

Storage Device is a device for recording (storing) information (data). Recording can be done using virtually any form of energy.storage device is a hardware device capable of storing information. There are two storage devices used in computers; a primary storage device such as computer RAM and a secondary storage device such as a computer hard disk drive.

Primary Storage: - Primary storage is a storage location that holds memory for short periods of times while the computer is on. For example, computer RAM (random-access memory) and cache are both examples of a primary storage device. This type of storage is the fastest type of memory in your computer and is used to store data while it’s being used. For example, when you open a program data is moved from the secondary storage into the primary storage. It is also known as internal memory and main memory.

 Secondary Storage: - Secondary storage is a storage medium that holds information until it is deleted or overwritten regardless if the computer has power. For example, a floppy disk drive and hard disk drive are both good examples of secondary storage devices. As can be seen by the below picture there are three different types of storage on a computer, although primary storage is accessed much faster than secondary storage because of the price and size limitations secondary storage is used with today’s computers to store all your programs and your personal data.

It is also known as external memory and auxiliary storage. Off-line storage in Fig  could be considered secondary storage, we’ve separated these into their own category because these types of media can be easily removed from the computer and stored elsewhere.

Floppy Disk : It’s a circular disk coated with magnetic oxide and enclosed within square plastic cover (Jacket). It’s available in different size, but the most commonly used floppy is 3½. Data up to 1.44 MB can be stored in it. Data is written as tiny magnetic spots on the dish surface creating new data or a disk surface eraser data previously stored at that location. Floppies are available in 2 sizes, 3.5 inch & 5.25 inch. The 3.5 inch size floppy is mostly used. The 5.25 inch floppy is kept in a flexible cover & it’s not safe. It can store about 1.2 MB data.

Hard Disk : Hard disks are made of aluminum or other metal alloys which are coated on both sides with magnetic material. Unlike floppy disks, hark disks are not removable from the computer. To remain the storing capacity several disks are packed together & mounted on a common drive to form a disk pack. A disk is also called a platter.

Magnetic Tape: Magnetic Tape can be used to perform both functions -input and output. Magnetic Tape is a secondary storage media. Magnetic tapes are used for large computers like mainframe computers where large volume of data is stored for a longer time. In PC also you can use tapes in the form of cassettes. The cost of storing data in tapes is inexpensive. Tapes consist of magnetic materials that store data permanently. It can be 12.5 mm to 25 mm wide plastic film-type and 500 meter to 1200 meter long which is coated with magnetic material. The deck is connected to the central processor and information is fed into or read from the tape through the processor. It similar to cassette tape recorder.

Advantages of Magnetic Tape:

• Compact: A 10-inch diameter reel of tape is 2400 feet long and is able to hold 800, 1600 or 6250 characters in each inch of its length. The maximum capacity of such tape is 180 million characters. Thus data are stored much more compactly on tape.

• Economical: The cost of storing characters is very less as compared to other storage devices.

• Fast: Copying of data is easier and fast.

• Long term Storage and Re-usability: Magnetic tapes can be used for long term storage and a tape can be used repeatedly with out loss of data. 

Magnetic Disk: You might have seen the gramophone record, which is circular like a disk and coated with magnetic material. Magnetic disks used in computer are made on the same principle. It rotates with very high speed inside the computer drive. Data is stored on both the surface of the disk. Magnetic disks are most popular for direct access storage device.

Each disk consists of a number of invisible concentric circles called tracks. Information is recorded on tracks of a disk surface in the form of tiny magnetic spots. The presence of a magnetic spot represents one bit and its absence represents zero bit. The information stored in a disk can be read many times without affecting the stored data. So the reading operation is non-destructive. But if you want to write a new data, then the existing data is erased from the disk and new data is recorded.

Optical Disk : Information is written to or read from an optical disk or tape using laser beam. Optical disks are not suitable memory storage units because their access time is more than that of hard disks. Their advantage is that they have very high storage capacity.

Types of optical memory are: CD –ROM, CD-R, CD-RW, DVD-ROM, DVD-R and DVD-RW. Information on a CD-ROM is written at the time of manufacture. CD-R/W of 700 MB are available. A DVD-ROM is similar to CD-ROM. It uses shorter wave length of laser beam and hence, stores more data than CD-ROM.

With every new application and software there is greater demand for memory capacity. It is the necessity to store large volume of data that has led to the development of optical disk storage medium. Optical disks can be divided into the following categories:

1. Compact Disk/ Read Only Memory (CD-ROM): CD-ROM disks are made of reflective metals. CD-ROM is written during the process of manufacturing by high power laser beam. Here the storage density is very high, storage cost is very low and access time is relatively fast. Each disk is approximately 4 1/2 inches in diameter and can hold over 600 MB of data. As the CD-ROM can be read only we cannot write or make changes into the data contained in it.

2. Write Once Read Many (WORM): The inconvenience that we can not write any thing in to a CD-ROM is avoided in WORM. A WORM allows the user to write data permanently on to the disk. Once the data is written it can never be erased without physically damaging the disk. Here data can be recorded from keyboard, video scanner, OCR equipment and other devices. The advantage of WORM is that it can store vast amount of data amounting to gigabytes (109 bytes). Any document in a WORM can be accessed very fast, say less than 30 seconds.

3. Erasable Optical Disk: These are optical disks where data can be written, erased and re-written. This also applies a laser beam to write and re-write the data. These disks may be used as alternatives to traditional disks. Erasable optical disks are based on a technology known as magnetic optical (MO). To write a data bit on to the erasable optical disk the MO drive's laser beam heats a tiny, precisely defined point on the disk's surface and magnetizes it.

Chapter : Memory & Input/Output Unit
• Computer Fundamental  

Interrupt - What is Interrupt? Types of Interrupts

                When a Process is executed by the CPU and when a user Request for another Process then this will create disturbance for the Running Process. This is also called as the Interrupt. Interrupts can be generated by User, Some Error Conditions and also by Software’s and the hardware’s. But CPU will handle all the Interrupts very carefully because when Interrupts are generated then the CPU must handle all the Interrupts Very carefully means the CPU will also Provides Response to the Various Interrupts those are generated. So that When an interrupt has Occurred then the CPU will handle by using the Fetch, decode and Execute Operations.

                                                         Types of Interrupts

Generally there are three types o Interrupts those are Occurred For Example

1)   Internal Interrupt

2)   Software Interrupt.

3)   External Interrupt.

The External Interrupt occurs when any Input and Output Device request for any Operation and the CPU will Execute that instructions first For Example When a Program is executed and when we move the Mouse on the Screen then the CPU will handle this External interrupt first and after that he will resume with his Operation.

The Internal Interrupts are those which are occurred due to Some Problem in the Execution For Example When a user performing any Operation which contains any Error and which contains any type of Error. So that Internal Interrupts are those which are occurred by the Some Operations or by Some Instructions and the Operations those are not Possible but a user is trying for that Operation. And The Software Interrupts are those which are made some call to the System for Example while we are Processing Some Instructions and when we wants to Execute one more Application Programs.

Storage Devices

                   As we know that the Main Memory Stores the data in a Temporary Manner means all the data will be loss when the Power switched off. And all the data will be loss when the power goes switched off.

So that we uses the Secondary Storage devices those are used for Storing the data in a Permanent Manner means all the Data will remain Stored whether the Power is Switched on or Switched off means the Power Will never effect on the System. For storing the data in a Permanent Manner we uses the Magnetic Storage Devices. There are also Some Advantages of Secondary Storage Devices.

1) Non-Volatile Storage Devices: The Non-Volatile Storage Devices are Non-Volatile in the nature means them never loss their data when the Power goes switched off. So that data which is Stored into the Non-Volatile Storage Devices will never be Loosed When the Power Switched off.

2) Mass Storage: The Capacity of these Devices is very high means we can Store the Huge Amount of data into the Secondary Storage Devices. We can Store data into the Secondary Storage Devices in the form of Giga Bytes and Tera Bytes.

3) Cost Effective: The Cost of Secondary Storage Devices is very lower in compare to the Main Memory So that they are also called as the more cost effective and they are very small and couldn’t easily damage. And the data can’t be easily loss from these Disks.

4) Reusability: As Memory Contains the Data in the Temporary as well as Permanent Manner. But the Secondary Storage Devices are always Reusable means they can be erased and stored any Time. Means we can add or Remove the Contents from these Disks when we Requires.

There are Many Types of Storage Devices those are based on the Sequential and Random Access Means the data which is Stored into the Secondary Storage devices can be Read either from the First Location which is also known as the Sequential Access or Sequential Manner and the Data can be Read from these Disks and also from any Locations. So if any Disk provides this Utility then this is called as the Direct Access Mechanism. There are Many Storage Devices those are either based on the SASD or Some are DASD.

Various types of Secondary Storage Devices are as Followings: -

1) Magnetic Tapes: The Magnetic Tapes is the Type of Secondary Storage Device and this Device is used for taking back up of data and this Tape contains some magnetic fields and the Magnetic Tapes are used Accessing the data into the Sequential Form and the Tape Also Contains a Ribbon which is coated on the Single Side of the Tape and also contains a head which reads the data which is Recorded on to the Tape. And when we are reading the information from the disk then we can also read backward information means we can also back the Tape for Reading the Previous information. And For inserting the Tape into the System we also Requires Some Tape Drives Which Contains Tape and which is Responsible for Reading the contents from the Tapes.

They can Store huge Amount of data into the Tape Drive , But the Main Limitation of the Tape Drive is that we cant Access the Data from the Disks directly means if we wants to 100th Record from the Tape then we must have to move all the Previous i.e. 99th Records first. And the Tapes are also easily damaged due to the Human Errors.

2) Magnetic Disks : - This is also called as the hard disk and this is made from the thin metal platter which is coated on the both sides of the magnetic Disks. And the there are Many Plates or Platters into a single Hard Disk and all the Plates are Made from the Magnetic Materials and all the Disks are Rotate from the 700 to 3600 rpm means Rotation per Minute and the Hard Disk also Contains a head which is used for both Reading and Writing the Data from the Hard Disks.

The Plate of Disk is Divided into the Tracks and sectors and the collection of Tracks makes a Cylinder means all the Tracks of the Disk which a Consecutive Areas makes a Cylinder.

The Disk is first divided into the Number of Tracks and the Tracks are further divided into the sectors and the Number of Tracks Makes a Cylinder. All the data is Stored into the disk by using Some Sectors and each sectors belongs to a Tracks. The Data is accessed from the Disk by using the heads, all the heads have Some Arm those are used for Reading the Data from the Particular Tracks and sector. When the Disk Rotates very high Speed then the Head also Moves, For Reading the data from the Disk the ARM touches with the Particular Track and read the data from that Location.

For Locating a Particular data from the Disk the head Moves Around the Disk very Fastly and data which a user wants to Access must have an Address So that Arm of the head just use that Address Means the Number of Cylinder, Number of Track and Number of Sectors from which user wants to read the data. With the Help of these Read and Write heads we can also Read the Data from the Disk and we can also Stores some data onto the Disk. Some Time Considerations are also used when we are accessing or storing the data onto the hard disk.

1)  Seek Time: - The Total Time which is Taken to Move on the Desired track is known as the seek Time. And time is always measured by using the Milliseconds.

2)  Latency Time. : The time required to Bring the Particular Track to the Desired Location Means the Total Time to bring the Correct the Sector for Reading or for the read and Write head. This is also called as the Average Time.

3)  Data Transfer Time: The Total Time which is required for Reading and Writing the data into the Disk is known as the Data transfer Time.

When we are Taking About the Magnetic Tapes then we can say that the Storage Capacity of the disk is Measure in the Form of Mega Bytes and when are talking about the Hard Disk then the Measurement will be in the Form of Giga Bytes. Means the Capacity of t the Hard Disk will be Read by using the Giga Bytes. The Magnetic Tapes are Sequential Access Device and the Hard Disk is the Direct Access Device means the data of this Disk will be Read from Any Location and the Data can be Read from the Disk by using the Read Write Heads. But hard Disks are Costlier than the Simple Magnetic Tapes. But the capacity of the Hard Disk is very high in compare to the Tapes.

3) Floppy Diskette: Floppy disk is a kind of storage device that can be used to  carried around? The Floppy Disk is also a Secondary Storage device which is used for storing the data in a Permanent Manner. The floppy is made up of Rigid Mylar Plastic and also contains a Magnetic black disk inside the Plastic Cover. The Floppy Disk also Stores all the Data into the Form of Tracks and Sectors and the floppy Disk provides both Reading and Writing the data into the Disk. The Floppy Disk is also called as Reusable Disk means the Floppy Disk Provides us the Facility to Read and Writes the Data into disk as and When Necessary and Also Many Times. We can Read and Write the data from the Disk.

The Main Advantage of the Floppy Disk is that the Data can be Stored many Times but the Main Limitation of the floppy Disk is that floppy Disk have a Small capacity and the Floppy Disk also doesn’t have Reliability means the Data Stored into the Disk may not be used for Long Time because the floppy Disk is very Sensitive Thing when we Move the Head of the Disk Again and Again then the floppy disk gets Damaged. So that we can say that Floppy Disk is not a Reliable thing. And I the Other side the Cost of floppy Disk is also high means with the Comparison of the Other Storage Media’s Floppy Disk have some more cost.

But the Main Advantage of the Floppy Disk is that floppy Disk is used for Moving the data from one Computer to Another With the Advent of the Floppy Disk we can Store the Data Into the Floppy Disk and after that we can Easily Remove that Disk from the System and Also Put the Disk into the Another System for Taking the Data.

But we can not Start or Run the System without the Hard Disk So that floppy Disk is used to Transfer the Files from one System into the. There are Two Types of floppy Disk Available first is the 3.5 and second is the 5.2. But for inserting the Floppy Disk into the System we must have to use the Floppy Disk Drive in the System.

For Reading the data from the Disk there are also Some Read and Write heads those are too used. And the Head will touch the Surface of the floppy Disk So that this will lead to the Damage of the Disk So Quickly because when the Head Directly Touch the Surface of the Disk, then this will lead to the Scratches on the Disk and also cause Damage of the Disk. And the Drive can take only one Disk Means we can insert only one Floppy Disk at a Time into the Floppy Drive. The capacity of the floppy Disk is 1.44 MB. So that we can Floppy Disks as rare as Possible.

Floppy Disk Contains a Notch which Specify Whether the data will be Read or Write Means to Say if we wants to Protect our data then we can set the Notch of the Floppy Disk as a Read Only.

4) Optical Disks: The Optical Disks are also called as the CD-ROM’s means Compact Disk Read Only Memory which is also used for Storing the data into the Disk and this is called as the Optical Disk because the CD-ROM ‘s are made up of the Golden or Aluminum Material and the data is Stored on the Disk in the Form of the Tracks and Sectors. The Whole Disk is Divided into the Number of Tracks and the Single Track is Divided into the Number of Sectors and the Data is Stored into the Sectors and the Disk is Divided into the Sectors as the first Track Contains the Sectors in the huge Size and the Other Tracks contains the Sectors in a Small Manner. So that as the Disk grows the Disk is Divided into the Small Number of Tracks and the Sectors.

CD-ROM Contains the data Which is truly Read able means we cant edit the contents of the CD-ROM Means once Data has been Written into the CD , we can be able to Change the Contents of the Disk and the Data which is Stored on the Disk can be Any Time Read by the user. The CD-ROM provides us the Large Capacity in compare to the Floppy Disks and the CDROM can Store the Data from 650 MB to 800 MB means the data can be Store up to this Space.

There are Many Disks that cant be Erased once Written So they are also called as the WORM Disks Means the Write Once and Read Many Mane a user can just Write the data only one Time and then after that he can use that Disk Many Times but a user cant Edit or Change those Contents after they are Written into the File. So that these Disks are not Reusable. So that  these Types of Optical Disks are also called as the CD-ROM and also Some Times they are known as the CD-R Means the Read Only Disks because the data which is Written into these Types of Disks is never to be Erased.

Now these Days there are also Some CDs Available those are also called as the CD-RW or Read Writable Disks. As the Name Suggest these Disks Provides the feature to the user to Read and Write the Contents from the Disk as they feel Necessary So that the CD-RW are now Most Popular because a user can any Time Remove the Contents from the Disk and also he can store the new Contents into the Disk.

The CD-R and CD-RW both have Same Capacity and both these can be used for Transferring the Files from one System to another but the Main difference is that the cost. The CD-RW has Some More Cost in compare to the Simple CD or in Compare to the CD-R.

Winchester Disk

Another term for hard disk drive. The term Winchester comes from an early type of disk drive developed by IBM that had 30MB of fixed storage and 30MB of removable storage; so its inventors called it a Winchester in honor of its 30/30 rifle. Although modern disk drives are faster and hold more data, the basic technology is the same, so Winchester has become synonymous with hard.

Magnetic Drum

A direct-access, or random-access, storage device. A magnetic drum, also referred to as drum, is a metal cylinder coated with magnetic iron-oxide material on which data and programs can be stored. Magnetic drums were once used as a primary storage device but have since been implemented as auxiliary storage devices.

The tracks on a magnetic drum are assigned to channels located around the circumference of the drum, forming adjacent circular bands that wind around the drum. A single drum can have up to 200 tracks. As the drum rotates at a speed of up to 3,000 rpm, the device's read/write heads deposit magnetized spots on the drum during the write operation and sense these spots during a read operation. This action is similar to that of a magnetic tape or disk drive.

Unlike some disk packs, the magnetic drum cannot be physically removed. The drum is permanently mounted in the device. Magnetic drums are able to retrieve data at a quicker rate than tape or disk devices but are not able to store as much data as either of them.

Chapter : Memory & Input/Output Unit
• Computer Fundamental 

What is CISC and RISC? Explain RISC in detail

                           

                       CISC (Complex Instruction Set Computer) : It was developed by Intel. CISC is a type of design for the computers. CISC based computer will have shorter programs which are made up of symbolic machine language.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                     A Complex Instruction Set Computer (CISC) supplies a large number of complex instructions at the assembly language level. During the early years, memory was slow and expensive and the programming was done in assembly language. Since memory was slow and instructions could by retrieved up to 10 times faster from a local ROM than from main memory, programmers tried to put as many instructions as possible in a microcode. 

RISC (Reduced Instruction Set Computer) : RISC is a type of microprocessor that has a relatively limited number of instructions. It is designed to perform a smaller number of types of computer instructions so that it can operate at a higher speed (perform more million instructions per second, or millions of instructions per second). Earlier, computers used only 20% of the instructions. Making the other 80% unnecessary. One advantage of reduced instruction set computers is that they can execute their instructions very fast because the instructions are so simple.

RISC chips require fewer transistors, which makes them cheaper to design and produce. In a RISC machine, the instruction set contains simple, basic instructions, from which more complex instructions can be composed. Each instruction is of the same length, so that it may be fetched in a single operation. Most instructions complete in one machine cycle, which allows the processor to handle several instructions at the same time. This pipelining is a key technique used to speed up RISC machines.

  

Advantages :

i) Speed : Since a simplified instruction set allows for a pipelined, superscalar design RISC processors often achieve 2 to 4 times the performance of CISC processor using comparable semiconductor technology and the same clock rates.

ii) Simpler Hardware : Because the instruction set of a RISC processor is so simple, it uses up much less chip space; extra functions, such as memory management units or floating point arithmetic units, can also be placed on the same chip. Smaller chips allow a semiconductor manufacturer to place more parts on a single silicon wafer, which can lower the per-chip cost dramatically.

iii) Shorter Design Cycle : Since RISC processors are simpler than corresponding CISC processors, they can be designed more quickly, and can take advantage of other technological developments sooner than corresponding CISC designs, leading to greater leaps in performance between generations.

What are Impact and Non-Impact Printers ?

                      

                         A printer is an output device that prints characters, symbols, and perhaps graphics on paper. The printed output is generally referred to as hardcopy because it is in relatively permanent form. Softcopy refers to temporary images such as those displayed on a monitor. Printers are categorized according to whether or not the image produced is formed by physical contact of the print mechanism with the paper. Impact printers have contact; nonimpact printers do not.

Impact printers

An impact printer has mechanisms resembling those of a typewriter. It forms characters or images by striking a mechanism such as a print hammer or wheel against an inked ribbon, leaving an image on paper. Impact printers are dying out; however, you may still come in contact with a dot-matrix printer. A dot-matrix printer contains a print head of small pins that strike an inked ribbon, forming characters or images. Print heads are available with 9, 18, or 24 pins; the 24-pin head offers the best print quality.

Dot-matrix printers permit a choice between output of draft quality; a coarser-looking 72 dots per inch vertically, which may be acceptable for drafts of papers and reports, and near-letter-quality, a crisper-looking 144 dots per inch vertically, which is more suitable for a finished product to be shown to other people.

Dot-Matrix Printers

Dot-matrix printers print about 40-300 characters per second (cps) and can print some graphics, although the reproduction quality is poor. Color ribbons are available for limited use of color. Dot-matrix printers are noisy, inexpensive, and they can print through multipart forms, creating several copies of a page at the same time, 

Daisy-Wheel Printer

A type of printer that produces letter-quality type.daisy-wheel is a serial printer A daisy-wheel printer works on the same principle as a ball-head typewriter. The daisy wheel is a disk made of plastic or metal on which characters stand out in relief along the outer edge. To print a character, the printer rotates the disk until the desired letter is facing the paper. Then a hammer strikes the disk, forcing the character to hit an ink ribbon, leaving an impression of the character on the paper. You can change the daisy wheel to print different fonts.

Daisy-wheel printers cannot print graphics, and in general they are noisy and slow, printing from 10 to about 75 characters per second. As the price of laser and ink-jet printers has declined, and the quality of dot-matrix printers has improved, daisy-wheel printers have become obsolete.

Drum Printer

An impact printer in which a complete set of characters for each print position on a line is on a continuously rotating drum behind an inked ribbon, with paper in front of the ribbon; identical characters are printed simultaneously at all required positions on a line, on the fly, by signal-controlled hammers.

Chain Printer

It is the character printer. The print element in a chain printer is a metallic band or chain containing the embossed characters that rotates horizontally in front of paper. A complete chain consists of the five sections; each section consists of 48 characters. As the print chain rotates, properly timed print hammers strike the paper along with linked ribbon, against the proper character on the chain as it passes. Chain printer are one of the fastest impact printers that can produce up to 400 to 2500 characters per second. Chain Printer also called band printers, contain characters on a rotation band. Speeds of up to 3000 lines a minute may be possible with these machines.

Line Printer

A high-speed printer capable of printing an entire line at one time. A fast line printer can print as many as 3,000 lines per minute. The disadvantages of line printers are that they cannot print graphics, the print quality is low, and they are very noisy.

Other Impact Printer Are

1. wire matrix printer - an impact printer in which each character is represented by a pattern of dots made by wires
2. wang image printer devices an output composed of a series of dots

Nonimpact Printers

Nonimpact printers, used almost everywhere now, are faster and quieter than impact printers because they have fewer moving parts. Nonimpact printers form characters and images without direct physical contact between the printing mechanism and the paper.

Two types of nonimpact printers often used with microcomputers are laser printers and ink-jet printers.

Laser Printer:

Like a dot-matrix printer, a laser printer creates images with dots. However, as in a photocopying machine, these images are created on a drum, treated with a magnetically charged ink-like toner (powder), and then transferred from drum to paper.
- There are good reasons why laser printers are so popular. They produce sharp, crisp images of both text and graphics, providing resolutions from 300 dpi up to 1200 dpi, which is near-typeset quality (NTQ). They are quiet and fast. They can print 4-32 text-only pages per minute for individual microcomputers, and more than 120 pages per minute for mainframes. (Pages with more graphics print more slowly.) They can print in many fonts (type styles and sizes). The more expensive models can print in different colors.

- Laser printers have built-in RAM chips to store documents output from the computer. If you are working in desktop publishing and printing complicated documents with color and many graphics, you will need a printer with a lot of RAM. Laser printers also have their own ROM chips to store fonts and their own small dedicated processor. To be able to manage graphics and complex page design, a laser printer works with a page description language, a type of software that has become a standard for printing graphics on laser printers. A PDL (page description language) is software that describes the shape and position of letters and graphics to the printer. PostScript, from Adobe Systems, is one common type of page description language; HPGL, Hewlett-Packard Graphic Language, is another.

Ink-jet printer:

Like laser and dot-matrix printers, ink-jet printers also form images with little dots. Ink-jet printers spray small, electrically charged droplets of ink from four nozzles through holes in a matrix at high speed onto paper.

- Ink-jet printers can print in color and are quieter and much less expensive than a color laser printer. However, they are slower and print in a somewhat lower resolution (300-720 dpi) than laser printers. Some new, expensive ink-jet printers print up 1200 or 1400 dpi. High resolution output requires the use of special coated paper, which costs more regular paper. And, if you are printing color graphics at a high resolution on an ink-jet printer, it may take 10 minutes or more for a single page finish printing.

- A variation on ink-jet technology is the bubble-jet printer, which use miniature heating elements to force specially formulated inks through print heads with 128 tiny nozzles. The multiple nozzles print fine images at high speeds. This technology is commonly used in portable printers.

plotter

A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers. It is now commonplace to refer to such wide-format printers as "plotters,"

plotter is a device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolor plotters use different-colored pens to draw different colors.

In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.

Chapter : Memory & Input/Output Unit
• Computer Fundamental  

Printer and different types of Printers

What is a Printer and what are the different types of Printers?

 

Printers are Output devices used to prepare permanent Output devices on paper. Printers can be divided into two main categories :

 

Impact Printers : In this hammers or pins strike against a ribbon and paper to print the text. This mechanism is known as electro-mechanical mechanism. They are of two types.

(i) Character Printer

(ii) Line Printer

 

Character Printer : It prints only one character at a time. It has relatively slower speed. Eg. Of them are Dot matrix printers.

 

Dot Matrix Printer : It prints characters as combination of dots. Dot matrix printers are the most popular among serial printers. These have a matrix of pins on the print head of the printer which form the character. The computer memory sends one character at a time to be printed by the printer. There is a carbon between the pins & the paper. The words get printed on the paper when the pin strikes the carbon. There are generally 24 pins.

 

Laser Printer is a type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure.

This is also the way copy machines work. Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all. One uses an array of LEDs to expose the drum and the other uses LCDs. Once the drum is charged, however, they both operate like a real laser printer. One of the chief characteristics of laser printers is their resolution – how many dots per inch (dpi) they lay down.

The available resolutions range from 300 dpi at the low end to 1,200 dpi at the high end. In addition to text, laser printers are very adept at printing graphics, so you need significant amounts of memory in the printer to print high-resolution graphics. To print a full-page graphic at 300 dpi, for example, you need at least 1 MB (megabyte) of printer RAM. For a 600 dpi graphic, you need at least 4 MB RAM.

Because laser printers are non-impact printers, they are much quieter than dotmatrix or daisy-wheel printers. They are also relatively fast, although not as fast as some dot-matrix or daisy-wheel printers. The speed of laser printers ranges from about 4 to 20 pages of text per minute (ppm). A typical rate of 6ppm is equivalent to about 40 characters per second (cps).

 

Non-Impact Printers : There printers use non-Impact technology such as ink-jet or laser technology. There printers provide better quality of O/P at higher speed. These printers are of two types :

 

Ink-Jet Printer : It prints characters by spraying patterns of ink on the paper from a nozzle or jet. It prints from nozzles having very fine holes, from which a specially made ink is pumped out to create various letters and shapes. The ink comes out of the nozzle in a form of vapors. After passing through a reflecting plate, it forms the desired letter/shape at the desired place.

 

 

Chapter : Memory & Input/Output Unit
• Computer Fundamental