Which of the following is not valid pair of input devices ?

Question

Accepted Answer

The correct option is (4):
The correct option is Plotter, Mouse because this pair is the only one that violates the fundamental definition of an input device pair. An input device is any hardware component that sends data and control signals to a computer, allowing a user to interact with or feed information into the system. The Mouse is, correctly, an input device, serving as a primary pointing tool for navigating the graphical user interface. However, the Plotter is a dedicated **output device**. Its sole function is to produce large-format, high-quality, continuous-line graphic output, such as architectural blueprints or maps, by drawing on paper. Since the pair contains one input device (Mouse) and one output device (Plotter), it is the one pair that is **not** a valid pair of input devices.

The incorrect option is (1):
This is a valid pair of input devices because both the Light Pen and the Digital Camera are specifically designed to send data to the computer. The Light Pen is a pointing device that uses a photosensitive detector to select objects or draw directly on a display screen, thereby inputting positional data. Similarly, the Digital Camera is an input device that captures real-world images and videos, converting them into digital data. This digital data is then transferred into the computer's memory for storage and processing. Both devices' primary role is to convert physical or light-based information into a digital format that the computer can use.

The incorrect option is (2):
The pair Scanner, Microphone is also a valid pair of input devices. The Scanner is an input device used to convert physical documents or photographs into digital image data that the computer can interpret, essential for digitization. The Microphone functions as an acoustic input device, converting sound waves into electrical signals which are then digitized and sent into the system for recording or voice commands. Both devices are indispensable tools for capturing external data—one for visual or hard-copy information, and the other for auditory information—making them clearly identifiable as input hardware.

The incorrect option is (3):
This pair, Trackball, Joy-stick, consists entirely of input devices and is therefore a valid pairing. The Trackball is essentially an upside-down mouse, serving as an alternative pointing and positioning input device where the user rolls a ball embedded in a stationary holder to control the cursor. The Joy-stick is a specialized input device used primarily for gaming or controlling machinery, allowing the user to input direction and movement commands with precision. Since the primary function of both devices is to translate human manipulation and control into digital signals for the computer, they are both classified as input hardware.