IT Skills Chapter 3 (2020)

Q: What are the input and output devices of the computer?

Input Devices:


An input device is any hardware component that allows users to input data or instructions into the computer.

Methods of inputting data & instructions:
There are two ways to enter data and instructions into the computer as following:

  1. Indirect Input.
  2. Direct Input.
  1. Indirect input:
    In indirect input method data is entered after intermediate handling. The most used indirect input devices are keyboard and pointing devices.
  2. Direct input:
    In this method data is entered directly into the computer system from the source. Devices used for direct input are called source data-entry devices. Most used direct input devices are scanning device, microphone and digital camera.

Q. What are the usages of input devices? List few of them?

Ans. Input Devices
The devices that are used to enter data and instructions into the computer are called input devices. The input device accepts input (data and programs) in a form that the computer can use, and then sends to the processing unit.

Types of Input Devices
Generally, the input devices are divided into three types:


Pointing devices

Source data-entry devices

List of most popular and commonly used input devices is as following:

  • Keyboard
  • Mouse
  • Scanners
  • Digital Camera

Q: What is an output and the functions of an output devices? List few of them.

Ans. Output devices:

The information generated by the computer after processing data is called output. The processed data into a useful form and then translated into a form that the users can understand, it is called output. The user views output on a screen, prints it on the printer or hears it through speaker. Computers can generate several types of outputs.

Types of output:

 These are classified into two categories as:

  • Hardcopy Output
  • Softcopy Output Or Sound Output
  1. Hardcopy Output:
    The output which is permanent and is not lost when the device generating it is turned off, is called hardcopy output. The output printed on a paper is called hardcopy output.
    The printers and plotters devices are used for this purpose.
  2. Softcopy Output Or Sound Output:
    The output which is not permanent and is lost when the device generating it is turned off is called softcopy output. The output received on the display screen or in the audio or video form, is called softcopy output. This kind of output is not tangible (real) and it cannot be touched. Sound is also a type of softcopy output.
    The output displayed on the computer screen is an example of softcopy output.

A list of commonly used output devices is given below: 

  • Monitors
  • Printers
  • Plotters
  • Speakers

Q. Briefly describes the working of various pointing devices?

Following is a brief description of working of various pointing devices: 

  • The mouse is rolled over a flat surface. Rolling of the mouse moves the pointer on the computer screen.
  • The trackball is a stationary device with a ball on its top.   The ball is rotated to move the pointer on the computer screen.

  • The touchpad is a flat, pressure-sensitive device. Sliding finger on the pad moves the pointer on the computer screen.

  • The pointing stick is a device positioned on the keyboard. Pushing the stick moves pointer on the computer screen.

  • The light-pen is a light-sensitive device. It is pointed at the screen to identify its position and moves pointer on the computer screen.

  • The touch screen is a touch-sensitive display. User interacts with the computer by touching areas of the screen. The pen-based system is used as a normal pen. However, writing with this system appears directly on the computer screen.

What are biometric devices?

Biometrics is the measurement and statistical analysis of people’s unique physical-and behavioral characteristics and the devices used to identify these biometric is called biometric devices.


A user identifying themselves to a computer or building by their fingerprint or voice is considered a biometrics identification. When compared to a password, this type of system is much more difficult to fake since it is unique for every person. Other common methods of a biometrics scan are a person’s face, Vein recognition, Fingerprints, ear, voice, hand, iris, and retina.


These devices are input devices as they input data into the computer about the biometrics. To Identify the unique patterns of biometric they come in many different sizes and shapes. The most well known is fingerprint these days. These systems are very reliable and more secure compared to passwords and keys because it is extremely difficult to fake these biometric features of a person since every person has unique biometric features.


  1. Fingerprint is being used by NADRA for CNIC data.
  2. Fingerprint sensors are also being added into smartphone as security.
  3. Fingerprint is being used by GSM companies by database of NADRA.
  4. Face Recognition & fingerprint is being used by companies to identify employee and automatic attendance system records when the employee arrived at company and when the employee left.
  5. School and Universities are also starting the biometric attendance with which students will be automatically be identified by face recognition and fingerprint. If the student is absent or skipping classes, this system automatically informs parents & management.
  6. Some companies use authorized person face recognition to unlock and open doors.

Student Note:
This answer has been given in details you can skip some point from all heading except definition. Definition is important.

Q.        Explain Refresh Rate, Resolution and Dot Pitch with reference of Computer Monitor & Video Card?            (2019-A, 2018.A)

Or       Describe various characteristics of display screens.

Ans. The display screens also known as CRTs, Monitors, or   simply screens are characterized according to their size   color, resolution, and video display adapter card.


 The size of the screen is measured diagonally from one corner to the other corner of the screen. Monitors come in different sizes, from small screen built into palmtops and laptop to extra-large monitors used for special purposes. The common sizes are 15, 17 19, 21 and 22 inches.  Color:   

            There are two types of display screens:


Screens display, information using a single foreground color and one background color.


  Screens display information in color. RGB stands for Red, Green and Blue. These screens use a combination of these colors to display color images on the screen. These RGB displays can create 256 colors and several thousand variations on them by blending shades of Red, Green, and Blue.


 The resolution is measured by the number of columns of pixels or dots and the number of rows of pixels a monitor can display. A screen with a resolution, for example, can display 640 columns and 480 rows of pixels. Resolution is a measure of sharpness and clarity of image displayed on the monitor. The number of dot or pixels per inch determines resolution or the sharpness of the image. A monitor with a higher resolution displays a greater number of pixels, which provides a smoother and clearer image.

Dot Pitch:   

The distance between one pixel on the screen and its next nearest pixel is known as dot pitch. The smaller the distance between the pixel, the sharper the displayed image. To minimize eye fatigue, a monitor with a dot pitch of 0.28 millimeters, or smaller   should be used.

 Refresh Rate:

  The images are drawn on the screen as an electron beam moves back and forth across the back of the screen and causes   pixels on the screen to glow. These’ pixels, however, glow for only a fraction of a second before beginning to -fade. The monitor thus   redraws the picture many times per second, so the image does not fade. This is called refreshing. If the screen is not refreshed rapidly, the screen appears to   flicker. The speed with which the monitor redraws images on the screen is called the refresh rate. A monitor’s refresh rate should be fast enough to maintain a constant. Refresh rate is measured by the number of times per second the screen is redrawn, called hertz. A high-quality monitor should provide a refresh rate of at least 75 hertz. This means the image on the screens redraws itself 75 times in one second.

Q: Define speaker?

Ans.  A computer speaker is an output hardware device that connects to a computer to generate sound.

Function of a Speaker:
Function of the speaker is to output data that the computer sends to it in audio-sounds. The signal used to produce the sound that comes from a computer speaker is created by the computer’s sound card.

Further explanation:
The computer sends a signal through its sound card to the speaker to produce sound. Computer sends digital signal (in the form of 0s and 1s) which speaker cannot understand directly so the sound card converts the signal to analog signal which then speaker uses to produce sound. Sound card is necessary for a computer to work with any speaker. (Now a days sound cards come build-in motherboard so you won’t require a separate sound card).

Speakers Structure:
Speakers are made up of a cone, an iron coil, a magnet, and housing (case). When the speaker receives electrical input from a device, it sends the current through the iron coil causing it to move back and forth. This motion then vibrates the outer cone, generating sound waves heard by our ears.

1.    For voice chatting & video conferencing

2.    For hearing sound data.

3.    For hearing recordings etc

Q. What is VDA? Explain different types of VDA?

Ans. Video Display Adapters:
To display graphics on a display screen it must have a Video Display Adapter attached with the computer. It is known as a video graphics card. Video graphic card is a circuit board that determines the resolution, number of colors, and speed with which images appear on the display screen.

Types of Graphic Card:
So far, there are three types of graphics cards introduced:

  1. VGA: Video Graphics Array, support 16-256 colors, depending on, screen I resolution. At 320 x 200 pixels, it will’ support 16 colors and at 640 x 480 pixels, 256 colors. It is called 4-bit color.
  • SVGA: Super Video Graphics Array, support 256 Colors at higher, resolution than VGA. It has two   graphics modes: 800 x 600 pixels and 1024 x 768   pixels It is called 8-bit color.
  • XGA: Extended Graphics Array, supports up to   16.7 million colors at a resolution of 1024 x 768 pixels. Depending on the video display adapter memory chip, XGA will support 256, 65536, or 16,777,216 colors. It is called 24-bit color or True color.

Student Note:

  1. Currently there are many more types but this book and syllabus hasn’t been update for many years. HDMI, Display port & DVI are new current main standards.
    The newest is mini display port and C port (USB C Port).
  • The difference in color represent that heading or paragraph can come as a separate short question.

Q: What are Mobile Devices?

Ans: In the computer world, the term mobile device refers to any electronic device that can be easily moved from one location to another. Over time, this category has expanded to include cell phones, laptops, smartphones, smartwatches and many other portable devices.


These devices are less powerful compared to their desktop or tower counterparts such as Desktop computers.
These devices are powerful enough to perform everyday tasks but they can not perform any high processing tasks such as to process data or store data of a complete country.
These devices are used for checking emails, communicating with others such as calling and video calling etc., or to get education from online sources.


The most common examples of mobile devices today are Smart Phone, Smart Watches, tablet computer & Laptop computer.

All the above images are examples of mobile device or mobile computer devices.

Mobile device history:

Laptops became one of the first mobile computing devices by eliminating the wires between the computer and its peripherals, by integrating them into one unit. The first laptop or portable computer was the IBM 5100, released in September 1975.

Today, mobile device usually refers to any hand-held computer capable of running apps that can connect to the Internet wirelessly. However, even by todays more scrupulous standards, the category keeps expanding with new inventions. As is true in any branch of computing, our mobile devices continue to offer more advanced functions while reducing size and weight.

Q: Describe CRT Monitors?

CRT Monitors:
A CRT monitor is a TV-screen-like device. This type of   monitor uses a cathode ray tube (CRT) to display images.

The screen of the monitor is coated with tiny dots of phosphor. The phosphor dots glow when they are electrically charged. An electronic beam generated by the CRT charges these dots.

A CRT consists of one or more guns which fire a beam of   electrons on the surface of the screen. The beam of electrons repeatedly falls on the surface of screen from top to bottom, dot by dot and line by line. Each beam-fall takes only a fraction of a second.

A stream of bits defining the image of output is sent from   the computer (from the CPU) to the graphic card from where it translates the signal & sends to CRT’s electron gun, where the bits are converted to electrons. The inside of the front of the CRT screen is coated with phosphor. When a beam of electrons from the electron gun hits the dots of phosphor, it lights up the selected pixels and an image of output is generated on the screen.

CRT in color displays consists of three guns, one each for red, green and blue color. These guns generate red, green and blue light on the screen. The combination of these three colors makes the full color spectrum and displays a color picture. These types of monitors are also called the RGB monitors.

Q.   Describe Flat-Panel Displays Screens.

Flat Panel Display:

A flat-panel display is a lightweight, thin screen. There are two types of flat panel displays. These are Liquid Crystal Display (LCD) and Gas Plasma Display.

Liquid Crystal Display (LCD) uses a liquid crystal display (LCD) to create an image on the screen. A liquid crystal display has special molecules deposited between sheets of glass. When an electric current pass through them, the molecules twist, causing some light waves to be blocked and allowing others to pass through. This creates the desired images on the screen.

Advantages and uses of Flat Panels:
LCD displays require less power and take up less space than the traditional CRT monitors. They are commonly used in portable computers, digital watches and calculators.

Gas Plasma Monitor:
Gas plasma monitor gas plasma technology. In this technology, a layer of gas is used in LCD monitor, when voltage is applied the gas which makes the required pixels to glow & form the image on the screen.

Gas plasma monitors offer larger screen sizes and higher display quality than LCD display screen. They are also much more expensive.

Difference in LCD Monitors and CRT Monitors
The main differences between CRT and LCD monitors are as follows:

CRT Monitors:

  1. They Cathode Rays Tube to display output on screen.
  2. They are very heavy compared to LCD Monitors.
  3. They required more energy such LCD monitors (such as 100w – 1800w depending on size)
  4. They cannot be used with less voltage systems directly such battery hence they are very high amount of voltages. They require high voltage transformer in them to power them.
  5. They were less expensive then LCD Monitors.
  6. They are very old and no longer being produced.

LCD Monitors:

  1. It uses Liquid Crystal Technology to display the output on screen
  2. Weights less then CRT Monitors.
  3. It is portable compared to CRT Monitors.
  4. It consumes less energy than CRT Monitors. (such as 30w to 120w).
  5. It requires less voltages to operate. (such as 3v to 48v).
  6. It was more expensive than CRT Monitors.
  7. Now a days these are widely used and known.

Q. What is active matrix LCD and passive matrix LCD?


(i) Active-matrix LCDs:
Active-matrix LCDs depend on thin film transistors (TFT). Basically, TFTs are tiny switching transistors and capacitors. They are arranged in a matrix on a glass substrate. To address a pixel the proper row is switched on, and then a charge is sent down to the correct column. Since all the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor can hold the charge until the next refresh cycle. And if we carefully control the amount of voltage supplied to a crystal, we can make it untwist only enough to allow some light through.
By doing this in very exact, very small increments, LCDs can create a gray scale. Most displays today offer 256 levels of brightness per pixel.

Passive-matrix LCDs:
Passive-matrix LCDs use a simple grid to supply the Charge to a particular pixel on the display. Creating the grid is quite a process! It starts with two glass layers called substrates, One substrate is given columns and the other is given rows made from a transparent conductive material. This is usually indium-tin oxide. The rows or columns are connected to integrated circuits that control when a charge is sent down a certain column or row. The liquid crystal material is sandwiched between the two glass substrates, and a polarizing film is added to the outer side of each substrate. To turn on a pixel, the integrated circuit sends a charge down that correct column of one substrate arid a ground activated on the correct row of the other. The row and column intersect at the designated pixel, and that delivers the voltage to untwist the liquid crystals at that pixel.

The simplicity of the passive-matrix system is beautiful, but it has significant drawbacks, notably slow response time and imprecise voltage control. Response time refers to the LCD’s ability to refresh the image displayed. The easiest way to observe slow response time in a passive-matrix LCD is to move the mouse pointer quickly from one side of the screen to the other. You will notice a series of “ghosts” following the pointer. Imprecise voltage control hinders the passive matrix’s ability to influence only one pixel at a time. When voltage is applied to untwist one pixel, the pixels around it also partially untwist, which makes images appear fuzzy and lacking in contrast. 

Q. What is difference Between Active-matrix display and passive-matrix?

Ans. Liquid crystal display (LCD) uses a liquid compound to present information on a display device.

LCD monitors-and LCD screens typically produce color using either active-matrix or passive-matrix technology.

(i) Active-matrix display:

An active-matrix display, also known as a TFT (thin-film transistor) display, uses a separate transistor to apply charges to each liquid crystal cell and thus displays high quality color that is viewable from all angles.

(ii) Passive-matrix display:

A passive-matrix display uses fewer transistors hence requires less power and is less expensive than an active-matrix display. The color on a passive-matrix display often is not as bright as an active matrix display. Users view images on a passive-matrix display best when working directly in front of it.


  • Active Matrix Displays:Active Matrix display are also known as TFT (Thin File Transistors) displays.They use less transistors then Passive matrix display.They produce high quality color output result which is viewable from all angles.They use more power than passive matrix displays.They are expensive then passive matrix displays.
  • Passive Matric Display:They use less transistors then Active matrix displaysThey are cheaper then Active matrix.They have high latency and take more time to refresh the image.They use less power than passive matrix. They output result quality is lower then active matrix and not clearly viewable from all angles.

Q: What is Bluetooth?



Bluetooth is a computing and telecommunications industry specification that describes how devices can communicate wirelessly with each other. Devices that use Bluetooth include computers, a computer keyboard and mouse, personal digital assistants, smartphones, handset, Bluetooth earphone, wireless headphones and many more devices.
Bluetooth is an RF technology that operates at 2.4 GHz & has an effective range Of 32—feet (10 meters) (this range varies On the power class), It can have transfer rate from 100kbps to 250mbs, its speed depends on the version and the distance.

How is Bluetooth used?

Example of how Bluetooth could be used is:
The ability to connect a computer to a smartphone or headphone without any wires or special connectors is the best example.

Uses of Bluetooth:
Below are few other examples of how Bluetooth can be used.

 Bluetooth headphones that can connect to any Bluetooth audio supported device.

Bluetooth keyboard and mouse can work as wireless keyboard and mouse.

Bluetooth speaker can connect to any Bluetooth audio device transmitting device.

Bluetooth car stereo system can make hands-free calls in the car.

Bluetooth watch or Bluetooth health monitor can transmit data over Bluetooth to other devices.

Bluetooth lock that can allow you to remotely lock and unlock a door.


Bluetooth is input and output device since it can input data from any Bluetooth input device such as Bluetooth camera and it can also output data through any Bluetooth output device. Such as Bluetooth printer.

Define Handset?

Ans: A single unit used for telephone calling which contain only small receiver speaker at the top, Microphone for voice transmitting and a dial pad with paid buttons or push buttons also called hand-held cellphone.

It was a portable, wireless phone and cordless phone, similar to a smartphone without all the smart features. Its design was that of the part of a desk telephone that is wire connected to telephone but to receive any calls it will be held to the ear and mouth containing the speaker (receiver) and microphone (transmitter) called telephone receiver. Headset had that look without the wire.

The handsets in some early phones contained only the speaker, such as this  at the turn of the 20th century. The microphone was in the base unit.

Just for reference for new generation that may not know how old telephones looked. These are some pictures:

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