Computer Input Devices – Groups, Categories & Typing Devices

Input Devices Overview

  • Definition: Pieces of equipment that allow data or instructions to be entered into a computer system.

  • Purpose/Significance: Serve as the primary bridge between the external world (users or sensing environments) and the computer’s internal processing units.

  • Contextual Connection: In prior lectures on the basic computer model, we saw that every computational cycle begins with input, followed by processing, storage, and output. Input devices therefore initiate the entire information-processing pipeline.

Classification of Input Devices

1. By Operational Group (Two Main Groups)

Group

Core Idea

User Involvement

Typical Use-Cases

Ethical/Practical Notes

Automated (sometimes labeled "automatic")

Device captures data without direct real-time human action.

None during capture\text{None during capture}

Sensors in IoT, barcode scanners on a conveyor belt, smart meters.

Raises data privacy questions (e.g. automated surveillance).

Manual (transcript appears as “Monical”)

Requires explicit human input actions to transmit data.

High\text{High}

Standard keyboards, mouse clicks, touch screen taps.

Emphasizes usability, accessibility (e.g. Braille keyboards).

2. By Functional Category (Five Main Categories)

Only Category 1 is explicitly listed in the current transcript. The lecture promises four additional categories (not yet visible on Page 1).

Category 1 – Typing Devices

Typing devices translate discrete human gestures (keystrokes or finger touches) into digital signals.

  • Standard (QWERTY) Keyboard
    • Most widespread alphanumeric input device.
    • Key matrix encoding sends scan codes that the CPU’s keyboard controller decodes.
    • Practical note: Rate-limiting (a.k.a. “debouncing”) prevents unintended double entries.
    • Ethical angle: Keyboard logging (key-loggers) threatens user privacy.

  • Braille Keyboard
    • Specially arranged keys representing the six-dot Braille cell.
    • Enables visually impaired users to type in Braille patterns that map to ASCII/Unicode.
    • Connection to accessibility design principles discussed in earlier classes (Universal Design, WCAG).

  • Touch Screen
    • A combined input–output surface: registers touches while simultaneously displaying feedback.
    • Technology stack:
    ◦ Resistive (pressure-based),
    ◦ Capacitive (electrostatic),
    ◦ Infra-red or Surface Acoustic Wave (SAW).
    • Hypothetical scenario: In a museum kiosk, a touch screen acts as a manual input device while also showing automated prompts tuned to user demographics.

  • “Garclard” Keyboard
    • Appears in transcript; likely a misspelling or brand-specific name (e.g. “Garboard”?)
    • Could refer to a gaming-centric or projection keyboard.
    • Lecturers often cite such niche devices to illustrate market segmentation.

Numerical / Technical Tidbits

  • A typical USB keyboard sends packets at 125 Hz polling rate (every 8 ms8\,\text{ms}).

  • Capacitive touch screens sample at 60−120 Hz60{-}120\,\text{Hz}; gaming phones may push 240 Hz240\,\text{Hz}.

  • Debounce algorithms may impose ≈5−20 ms\approx 5{-}20\,\text{ms} delays to filter key-bounce noise.

Anticipated Next Steps (based on five-category promise)

Although Page 1 only includes Category 1, the lecture outline suggests upcoming discussion of:

  1. Pointing Devices (mouse, trackpad).

  2. Scanning/Sensing Devices (barcode, OCR).

  3. Audio/Voice Input (microphone, voice assistants).

  4. Biometric/Optical Devices (fingerprint, camera).

Students should prepare by revisiting earlier readings on human-computer interaction and ergonomics to appreciate why diverse input modalities matter.