Essential Concept: Output is data from the computer in a form that is readable by people or useful to people. Without output, there would be no point in having a computer at all. Output devices convert processed data into human-readable or machine-readable formats that we can use and understand.
Key Definition: Output refers to the results of computer processing that are presented to users in various forms like text, images, sound, or control signals. Output devices are the hardware components that deliver these results.
Three Categories of Output
Human-Readable Output
Output designed for people to see and understand, such as:
- Text on a computer screen
- Printed documents
- Audio from speakers
- Images on displays
Purpose: To communicate information directly to human users in formats we can easily interpret.
Machine-Readable Output
Output designed to be input directly into another computer or machine, such as:
- Barcodes printed by computers
- QR codes
- Magnetic stripe data
- RFID signals
Purpose: To enable communication between machines without human intervention.
Control Signal Output
Output that controls machines and other devices, such as:
- Signals to industrial robots
- Control of manufacturing processes
- Home automation systems
- Vehicle computer controls
Purpose: To automate processes and control physical systems based on computer decisions.
Hard Copy
Definition: Printed output on physical media like paper
Examples: Printed documents, photographs, receipts
Advantages: Permanent, portable, doesn’t require power to view
Soft Copy
Definition: Electronic version of a document
Examples: Files on memory sticks, email attachments, on-screen documents
Advantages: Easy to edit, share electronically, searchable, environmentally friendly
Visual Display Units (VDUs / Monitors)
The image on a VDU is made up of thousands of tiny dots of light called pixels (picture elements). Each pixel can be controlled independently to create images, text, and video.
Pixel Demonstration: How pixels form images
Each square represents one pixel. When viewed from a distance, these pixels form recognizable shapes.
Low Resolution
Fewer, larger pixels
Image appears blocky or pixelated
Example: 640 × 480 pixels
High Resolution
More, smaller pixels
Image appears sharp and clear
Example: 1920 × 1080 pixels
Types of VDU Technology
| Technology | How It Works | Advantages | Disadvantages | Common Uses |
|---|---|---|---|---|
| LCD (Liquid Crystal Display) | Uses liquid crystals between polarized filters, with backlighting | Thin, lightweight, energy efficient | Limited viewing angles, backlight can fail | Laptops, desktop monitors, TVs |
| LED (Light Emitting Diode) | Uses LEDs for backlighting (LED-backlit LCD) or as individual pixels (OLED) | Better contrast, thinner, more energy efficient than LCD | More expensive, potential burn-in (OLED) | High-end monitors, smartphones, TVs |
| CRT (Cathode Ray Tube) | Electron beam scans phosphor-coated screen to create image | Excellent color reproduction, no native resolution | Bulky, heavy, high power consumption | Rarely used today (obsolete) |
| OLED (Organic LED) | Each pixel emits its own light (no backlight needed) | Perfect blacks, high contrast, thin, flexible | Expensive, shorter lifespan, potential burn-in | Premium smartphones, high-end TVs |
VDU Selection Tip: When choosing a monitor, consider: (1) Resolution (higher is better for detail), (2) Size (larger is easier to see but takes more space), (3) Refresh rate (important for gaming), (4) Panel type (IPS for color accuracy, TN for fast response), and (5) Connectivity (HDMI, DisplayPort, USB-C).
Printers: Creating Hard Copy Output
Printer Categories: Printers are broadly classified into two main categories based on how they create images on paper: Impact Printers and Non-Impact Printers. Impact printers physically strike the paper, while non-impact printers create images without physical contact.
Impact Printers
Impact printers have a print head that strikes an inked ribbon against the paper, similar to a typewriter. They typically print one character at a time and are known for being able to produce multiple copies using carbon paper.
Dot Matrix Printers: The most common type of impact printer. They use a grid of tiny pins (typically 9 or 24 pins) that strike an inked ribbon against paper to form characters and images from patterns of dots. The print head moves across the paper while the pins fire in specific sequences to create characters.
Key Characteristics of Dot Matrix Printers:
- Mechanism: Physical pins strike ribbon against paper
- Print Quality: Relatively low resolution (measured in characters per inch – CPI)
- Speed: Slow compared to modern printers (measured in characters per second – CPS)
- Noise Level: Very noisy due to mechanical impact
- Carbon Copies: Can produce multiple copies using carbonless paper
- Cost: Low operating cost, ribbons are inexpensive
Modern Use: Still used for invoices, receipts, and multipart forms where carbon copies are needed, as well as in environments requiring continuous feed paper.
Non-Impact Printers
Inkjet Printers
How they work: Spray microscopic droplets of ink onto paper through tiny nozzles
Speed: Moderate (pages per minute)
Quality: Excellent for color photos, good for text
Cost: Low initial cost, higher ink cost per page
Best for: Home use, photo printing, small businesses
Disadvantages: Ink can smudge when wet, cartridges can dry out if not used regularly
Laser Printers
How they work: Use laser to create static charge pattern on drum, attract toner (powdered ink), then fuse to paper with heat
Speed: Fast (many pages per minute)
Quality: Excellent for text and graphics, very sharp edges
Cost: Higher initial cost, lower per-page cost
Best for: Offices, high-volume printing, environments requiring many text documents
Advantages over inkjet: Faster printing speed, lower cost per page for high volume, better text quality, prints are immediately dry, more durable output
Thermal Printers
How they work: Use heated pins or elements to create images on specially coated heat-sensitive paper that changes color when heated
Speed: Fast and quiet operation
Quality: Good for text, limited graphics capability
Cost: Low initial cost, but special thermal paper is required
Best for: Receipts, labels, barcodes, fax machines, point-of-sale systems
Disadvantages: Output fades over time (especially in heat/sunlight), requires special paper, cannot produce color
Key difference from dot matrix: Thermal printers are completely silent (no impact mechanism) and use heat instead of physical striking to create images
Printer Comparison: Dot matrix printers are impact printers that physically strike paper, making them noisy but able to produce carbon copies. Thermal printers are non-impact printers that use heat on special paper, making them silent but with output that can fade. Laser printers use toner and heat fusion for high-quality, durable output ideal for office environments.
Exam Focus: Remember these key printer selection criteria: (1) Speed (pages per minute), (2) Quality (dots per inch – DPI), (3) Cost (initial vs. ongoing), (4) Color capability, (5) Special features (duplex printing, network connectivity). Be prepared to compare different printer types and justify selection for specific scenarios.
Specialized Output Devices
Plotters
A plotter works by moving a pen across a page to create precise technical drawings.
- Precision: More accurate than regular printers for technical drawings
- Media: Can handle large paper sizes (A0, A1) and various materials
- Movement: Pen moves in both X and Y axes to draw continuous lines
- Modern versions: Often use inkjet or electrostatic technology instead of pens
Applications: Architectural plans, engineering drawings, maps, circuit diagrams, CAD (Computer-Aided Design) output
3D Printers
Three-dimensional or 3D printing creates solid objects by adding thin layers of material on top of each other (additive manufacturing).
- A 3D digital model is created using CAD software or 3D scanning
- The model is “sliced” into thin horizontal layers by special software
- The 3D printer builds the object layer by layer, fusing material as it goes
- Common materials include plastic filament, resin, or metal powder
Applications: Prototyping, custom parts, medical implants, architectural models, educational tools, aerospace components
Revolutionary aspect: Digital files can be sent anywhere in the world and printed locally
Audio Output Devices
Speakers
Function: Convert electrical signals into sound waves for multiple listeners
Components: Amplifier, driver(s), enclosure
Types: Stereo (2 speakers), surround sound (5.1, 7.1), soundbars, Bluetooth
Best for: Group listening, movies, music, presentations
Headphones
Function: Personal audio output that covers both ears
Types: Over-ear, on-ear, noise-cancelling, wireless
Advantages: Private listening, blocks external noise, better sound isolation
Best for: Individual listening, noisy environments, audio editing
Earphones/Earbuds
Function: Small speakers that fit in or just outside the ear canal
Types: Wired, wireless (Bluetooth), true wireless (no connecting wire)
Advantages: Portable, lightweight, allows awareness of surroundings
Best for: Mobile use, calls, situations where you need to hear ambient sounds
Audio Quality Factors: When evaluating audio output, consider: (1) Frequency response (range of sounds), (2) Impedance (power requirements), (3) Sensitivity (loudness), (4) Distortion (clarity at high volume), and (5) Connectivity (wired vs. wireless).
Choosing the Right Output Device
| Scenario/Need | Recommended Output Device(s) | Key Considerations |
|---|---|---|
| Office document processing (high volume) | Laser printer, large monitor | Speed, text quality, cost per page, reliability for heavy use |
| Retail receipts and invoices | Thermal printer or dot matrix printer | Speed, quiet operation (thermal) or carbon copy capability (dot matrix), durability |
| Graphic design/photo editing | High-resolution monitor, color-accurate inkjet printer | Color accuracy, resolution, color gamut, calibration |
| Architectural/engineering work | Large format plotter, high-resolution monitor | Precision, large format capability, detail accuracy |
| Home entertainment | HD/4K TV or monitor, speakers or soundbar | Resolution, screen size, sound quality, connectivity |
| Prototyping/product design | 3D printer, high-resolution monitor | Material options, precision, build volume, software compatibility |
| Mobile computing | Lightweight monitor/tablet, portable speaker, headphones | Portability, battery life, connectivity, durability |
Quiz: Test Your Understanding
Examples:
Hard copy: Printed document, photograph
Soft copy: PDF file, email attachment, on-screen document
Key difference: Hard copies are permanent and portable without devices, while soft copies are easily editable and shareable electronically.
Impact Printers:
• Work by physically striking ink ribbon against paper
• Example: Dot matrix printer
• Advantages: Can create carbon copies, low operating cost
• Disadvantages: Noisy, slow, poor graphics quality
Non-Impact Printers:
• Create images without physical contact with paper
• Examples: Laser printer, inkjet printer, thermal printer
• Advantages: Quiet, faster, better quality, color capability
• Disadvantages: Higher initial cost, can’t make carbon copies
Modern preference: Non-impact printers are far more common today due to their superior quality and versatility.
1. Speed: Laser printers are faster (more pages per minute)
2. Cost-effectiveness: Lower cost per page for high-volume printing
3. Text quality: Superior for text documents and business graphics
4. Durability: Prints are immediately dry and resistant to smudging
5. Reliability: More durable for heavy use
6. Networkability: Easier to connect to office networks
7. Maintenance: Less frequent cartridge replacement
Inkjet printers are better for photo printing and low-volume home use but less economical for high-volume office environments.
1. Impact Printers: Work by physically striking an inked ribbon against paper
• Example: Dot matrix printer
• Mechanism: Print head with pins hits ribbon
• Characteristics: Noisy, can make carbon copies, lower quality
2. Non-Impact Printers: Create images without physical contact with paper
• Examples: Laser, inkjet, thermal printers
• Mechanism: Various (laser/toner, ink spraying, heat application)
• Characteristics: Quiet, higher quality, faster, cannot make carbon copies
Key difference: The fundamental distinction is whether the printer mechanism makes physical contact with the paper (impact) or creates images through other means like heat, ink spraying, or toner application (non-impact).
How 3D printing differs from traditional printing:
1. Dimensionality: 3D prints three-dimensional objects; traditional prints two-dimensional images on flat surfaces
2. Process: 3D uses additive manufacturing (building layer by layer); traditional is essentially 2D deposition of ink
3. Output: 3D creates physical objects; traditional creates images/text on paper
4. Materials: 3D uses plastic, resin, metal; traditional uses ink or toner
5. Applications: 3D for prototypes, parts, models; traditional for documents, photos
Applications of 3D printing:
1. Prototyping: Rapid creation of product prototypes for testing
2. Medical: Custom prosthetics, dental implants, surgical guides
3. Manufacturing: Custom parts, tools, low-volume production
4. Education: Teaching aids, models, STEM projects
5. Aerospace: Lightweight components for aircraft and spacecraft
Key Difference: Dot matrix printers are impact printers that physically strike an inked ribbon against paper using pins, making them quite noisy. Thermal printers are non-impact printers that use heated elements to create images on special heat-sensitive paper, operating silently.
Additional Differences:
• Mechanism: Dot matrix uses physical impact; thermal uses heat application
• Paper: Dot matrix uses regular paper; thermal requires special heat-sensitive paper
• Noise: Dot matrix is very noisy; thermal is completely silent
• Output longevity: Dot matrix output is permanent; thermal output can fade over time
• Carbon copies: Dot matrix can produce them; thermal cannot
Similarity: Both are often used for receipts and transaction records in business environments.
🎯 Key Concepts to Remember
- Output: Processed data presented in usable form
- Two main printer categories: Impact (physical striking) and Non-impact (no physical contact)
- Impact printer example: Dot matrix printer – noisy, makes carbon copies
- Non-impact examples: Laser, inkjet, thermal printers
- Laser vs. Inkjet: Laser is faster, better for text, lower cost per page for high volume
- Thermal printers: Silent, use heat-sensitive paper, output can fade
- Hard vs. Soft copy: Physical vs. electronic output
- VDU resolution: More pixels = clearer image
- Specialized output: Plotters for technical drawings, 3D printers for objects
- Audio output: Speakers (group), headphones (private), earphones (portable)
- Selection criteria: Consider purpose, volume, quality, cost, and environment
Exam Strategy: When answering output device questions, remember to: (1) Identify the correct device type, (2) Explain how it works simply, (3) List appropriate applications, (4) Compare advantages/disadvantages when relevant, and (5) Relate to real-world examples. For printer questions, always start by identifying whether it’s impact or non-impact technology.