Input and Output Devices (The Difference)



download (3)Computer Input and Output Devices

The process of getting information into and out of computers is called Input/Output or just I/O.

Devices used for Input/Output are called I/O devices.

INPUT DEVICES:

These are used to feed information into computer.

Keyboard:

 

  • It is the most common input device.
  • It has many keys on it so that’s why it is called keyboard.
  • It is just like a typewriter.
  • A standard keyboard has following special keys.

Function Keys:

These are from F1 to F12. These have special functions in each program.

CTRL and ALT Keys:

CTRL (Control)

ALT (Alternate)

These are always used with other keys to issue commands.

BACKSPACE Keys:

Deletes the immediate left character of the cursor.

Four Arrow Keys:

Used for changing direction.

PageUp and PageDown Keys:

Move the cursor one page up or down.

Home Key:

Move the cursor to the left of the screen or beginning of the document.

End Key:

Move the cursor to the right of the screen or end of the document.

Esc Key:

Esc (Escape)

Use to exit from your currently selected option.

Numeric Keys:

These keys are from 0 to 9.

Alphabetic Keys:

These are A to Z or a to z.

Mouse:

  • It is a pointing device.
  • By using mouse we can perform required task in a quick time.
  • It has a rubber ball in its base and two or three buttons on it.
  • It is normally used for

Picking some option Pointing some option Drawing

Microphone:

  • Microphones are used to record speech.
  • It makes communication (Voice chatting and Phone calls) very easy.
  • Microphones are also used in speech recognition (Voice Recognition) programs.
  • In speech recognition programs user can dictate to the computer instead of typing.

Video Cameras:

  • Used to capture images of any type.
  • After that video camera will be attach with computer and store images in computer.

Scanners:

  • Also used to capture images but only from paper.
  • Accuracy is much better than video camera.
  • Scanners are widely used to get Drawings, Diagrams and Photographs into computer systems for required task.

OUTPUT DEVICES:

These devices are used to return back data.

Monitor:

  • It is the most common output device.
  • Shape of monitor is just like a T.V set.
  • Function of monitor is to display output on its screen.
  • Any picture is made up of small dots called Pixels.
  • Two technologies used in monitor are Cathode Ray Tube (CRT)

Liquid Crystal Display (LCD) or Flat Screens

Cathode Ray Tube (CRT):

  • Most computer monitors are based on CRT.
  • A beam of electrons emitted by electron gun makes an image on screen.
  • In case of color monitor there are three electron guns one for each color that are RED, GREEN and BLUE (RGB).
  • In monochrome monitors displays text as either green on black background or white on black background. The foreground and background colors can be reversed by software.

Flat Screens or Liquid Crystal Display (LCD):

  • Liquid crystal displays (LCD) are flat screen.
  • Flat screen monitors having no electron gun.
  • Image will made up with the help of liquid.
  • This technology is very expensive.

PRINTERS:

  • Printers are used to produce hard copy of output.
  • Printers can print text and graphics.
  • Printers are available in both color and black & white.
  • The port of printer is called LPT1.
  • Main difference in printers depends on Quality of output

Ability to print graphics Printing speed

Character Printers:

  • Print one character at a time
  • It has slow speed.
  • It can print 30 to 300 characters per second (cps).
  • It has low cost.
  • It makes a lot of noise while printing.

Two types are

Dot Matrix Printer

Daisy Wheel Printer

Dot Matrix Printers:

  • It has normally 9 or 24 pins in the form of a matrix.
  • Pins hits the printer ribbon so that our required character will be print on paper.

Daisy Wheel Printers:

  • Print head of this printer is a circular wheel about 3-inches in diameter with arms.
  • Character shapes are made at the outer end of arms.
  • To print a character daisy wheel rotates so that required character is positioned in front of printer ribbon. Now arm will hot by a hammer and strikes the ribbon leaving an impression on paper.
  • Print quality is better than dot matrix.

Line Printers:

  • Print one complete line at a time.
  • Speed is faster than character printers.
  • Can print 200 lines per minute (LPM).
  • Types are Chain Printers &Drum Printers

Chain Printers

  • They use a rapidly moving chain.
  • Characters are linked with chain.
  • Required characters will be placed in front of paper then strike of hammer make impression on paper.

Drum Printers

  • Characters are engraved along the drum.
  • Drum rotates and required characters will be print on paper by strike of hammer.
  • Character and line printers are also called impact printers.

Non-impact Printers:

  • These are high speed and expensive printers.
  • Types are
  •   Laser Printers
  •  Inkjet Printers

Laser Printers:

  • Print one page at a time.
  • Can print 8 pages per minute.
  • Print quality is good.
  • Laser light, Roller and Toner (ink) are responsible for printing.

Inkjet Printers:

  • Print one page at a time
  • Printing is possible due to spray of ink.

PLOTTERS:

  • Just like printers but used to print large images such as Maps, Graphs, Charts.
  • Two types are
  • Flatbed Plotters
  • Drum Plotters

Flatbed Plotter:

  • Paper will fix over the flatbed table.
  • Pen-holding technology is used for printing.
  • Very slow method of printing.

Drum Plotters:

  • Paper will place on drum, which rotates the paperback and front.
  • Pen-holding technology is used for printing.

MEMORY:

  • It is used to store large amount of data.
  • Magnetic Tape and Magnetic Disk are very popular devices for storage.
  • Memory can be temporary or permanent.

MEMORY TERMINOLOGIES:

Memory Cell:

It is an electrical circuit used to store a single bit (0 or 1).

Memory Word:

  • Group of bits that represents information or data.
  • Word size ranges from 4 to 64 bits.

Byte:

Combination of 8 bits is called Byte.

Memory Capacity:

Way of specifying, how many bits can be stored in memory.

Explanation:

Suppose that we have memory size which can store 4096-20 bits words. This represents total capacity of 81,920 bits. This can be written as 4096×20.

Here,

4096= Number of words 20= Word Size

Units of Memory:

Unit of memory is byte. The larger units are Kilo Byte (KB), Mega Byte (MB), Giga Byte (GB) and Tera Byte (TB).

 

1Byte=8 bits
1Kilo Bytes=1024Bytes
1Mega Bytes=1024Kilo Bytes
1Giga Bytes=1024Mega Bytes

Address:

  • A location of words in memory is called address.
  • Each word has unique address.
  • Memory addresses are specified in binary numbers.

Read Operation

Read operation is used to fetch data from memory.

Write Operation:

Write operation is used to store data in memory.

Access Time:

It is the amount of time required to perform Read operation.

Cycle Time:

It is the amount of time required to perform Read or Write operation and then return to its original state ready for next operation.

Random Access Memory (RAM):

  • Data will read randomly.
  • Access time is same for any address.
  • It is a temporary memory.

Sequential Access Memory

  • Access time is not constant.
  • Access time is longer than random access time.
  • If we want to read 5th record then we must read first 4 records.
  • Example is Magnetic Tape.

Read/Write Memory (RWM):

Memory that can be read from or written into.

Read-Only Memory (ROM):

  • It is a permanent memory.
  • Data can read only.
  • Instructions are written at the time of creation/manufacturing.

Static Memory Devices:

Stored data will remain permanent as long as power is supplied.

Dynamic Memory Devices:

Stored data will not remain permanent even with power applied.

INFORMATION SYSTEM DEVELOPMENT (ISD):

Information systems are design for those people who have very little knowledge of information technology. The five phases of information system development are

System Analysis System Design

System Analysis:

Three task of this phase are

  • Defining the problem
  • Analyze current system
  • Selecting the best solution

System Design:

Analysis will convert into Charts and making User Manuals.

System Development:

  • Writing computer programs.
  • Testing and debugging programs.

System Implementation:

  • Install developed system on computers.
  • Training of operators and users.

System Maintenance:

After implementation if any error occurs then it will remove in this phase.

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