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Chapter - 4 : Input Unit

Updated: Apr 24

Subject: Computer Fundamentals | ▒



Input Unit


An input unit is one of the functional units of a computer system that accepts the list of instructions and data from the outside world, converts them into computer acceptable format (binary form), and supplies the converted data and instructions to the computer system for further processing.


Most commonly used input units are as follows:


1. Punched Card

  • Punched Card is one of the earliest used I/O media.

  • The standard punched card, originally invented by Herman Hollerith, was first used for vital statistics tabulation by the New York City Board of Health and several states.

  • It is a piece of stiff paper with a standard dimension of 19.3cm X 9.5cm X 0.018cm.

  • It is divided into 12 rows and 80 columns. Only one character can be recorded in each column. Thus, a total of 80 characters on a single punched card can be recorded.

  • In a punched card, a hole represents 1 and no hole represents 0.



2. Keyboard

  • The keyboard is the piece of computer hardware used to input text, characters, and other commands into a computer or similar devices.

  • Layout: Most keyboards are of the QWERTY type. Many different keyboard layouts are also available around the world like DVORAK and JCUKEN.

  • Connectivity: Wireless keyboards are communicating with the computer via Bluetooth or an RF Receiver. Wired keyboards connect to the motherboard via a USB cable, using the USB type A connector. Older keyboards connect via a PS/2 connection.

  • Different types of keys available in a computer keyboard:

(a) Alphabetic Keys: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

(b) Numeric Keys: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

(c) Special Character Keys: All the symbolic characters are known as special character keys.

(d) Function Keys: F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12.

(e) Special Function Keys: ENTER, Spacebar, Backspace, Delete, Tab, etc.

(f) Modifier Keys: SHIFT, ALT, CTRL.

(g) Navigation Keys: ← ↑ ↓ →



3. Mouse

  • A mouse is a pointing and clicking device (hand control) that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, which allows a smooth control of the graphical user interface.

  • The computer mouse as we know it today was invented and developed by Douglas Engelbart with the assistance of Bill English during the 1960s and was patented on November 17, 1970.

  • The computer mouse was first time used in 1976 by Apple Computers.

  • Different types of mouse used in a computer are as follows:

  1. Wireless Mouse

  2. G-Stick Mouse

  3. Optical Mouse

  4. Trackball Mouse

  5. Mechanical Mouse or Ball Mouse

  • Connectivity: Wired mouse use a thin electrical cord terminating in a standard connector like USB, PS/2, or serial ports. Wireless mouse can communicate with a computer system via Bluetooth, RF (Radio Frequency), or IR (Infrared).



4. Scanner

  • A scanner is a device that optically scans images, printed text, handwritten documents, or an object and converts it to a digital image.

  • Scanners communicate to their host computer using one of the following physical interfaces, listing roughly from slow to fast:

  1. Parallel Port

  2. GPIB (General Purpose Interface Bus)

  3. SCSI (Small Computer System Interface)

  4. USB (Universal Serial Bus)

  5. FireWire

  6. Proprietary Interfaces


  • Types of scanners:

  1. Drum Scanner

  2. Flatbed Scanner

  3. CCD Scanner

  4. CIS Scanner

  5. Film Scanner

  6. Roller Scanner

  7. 3D Scanner

  8. Planetary Scanner

  9. Hand Scanner

  10. Smartphone Scanner Apps


5. Microphone

  • A microphone is a device that translates sound vibrations in the air into electronic signals or scribes them to a recording medium. In other terms, the microphone allows us to input audio into a computer.

  • A microphone gives you the facility to transmit your voice when connected to a computer network or to record your voice so that you can use it in your presentation, as a message to answer the incoming calls (just like you do in an answering machine), etc.

6. Digital Camera

  • A digital camera is a hardware device that captures and stores photographic images in digital form. The digital image so formed can be stored in the computer.

  • It can capture images of high resolution, enough for large prints.

  • It is lighter in weight than its competitors like a film camera. And also memory cards are smaller in size and can store more images than a dozen rolls of film.

  • Captured photographs can be viewed immediately on the camera itself.

  • Many digital cameras offer built-in filters and editing options. You can also edit the images on the computer with the help of photo editing software.

7. Touchpad

  • A touchpad is a device that lays on the desktop and responds to the pressure.

  • A touchpad is a pointing-and-clicking device featuring a tactile sensor, a specialized surface that can translate the motion and position of a user's fingers to a relative position on the operating system that is made output to the screen.

  • It is also known as a trackpad.

  • It is a common feature of laptop computers.

  • It is also used as a substitute for a mouse where desk space is less.

8. Light Pens

  • A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT display.

  • It allows the user to point to a displayed object or draw on the screen in a similar way to a touchscreen but with greater positional accuracy.

  • It can work with any CRT-based monitor, but not with LCD screens, projectors, or other display devices.

9. Joystick

  • A joystick is an input device consisting of a stick that pivots on a base and reports its angle and direction to the device it is controlling.

  • It is often used to control video games and for controlling machines such as cranes, wheelchairs, etc.

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