A monitor (Visual Display Unit or VDU) is an output device that displays text, images, videos, and graphics generated by a computer. It allows users to see their work visually on a screen, making it the primary interface between the computer and the user.
Quick Summary
- Monitors convert electronic signals from computers into visible images
- Common types include CRT, LCD, LED, and OLED monitors
- Resolution determines image clarity (measured in pixels like 1920×1080)
- Refresh rate (measured in Hz) affects how smooth motion appears
- Modern monitors connect via HDMI, DisplayPort, or VGA cables
What is a Monitor?
The monitor is the screen you look at when using a computer. Just like a television screen, it shows pictures, text, and videos. Without a monitor, you cannot see what the computer is doing. When you type on the keyboard or move the mouse, the monitor displays the results immediately.
Monitors are called Visual Display Units (VDU) because they make computer information visible to your eyes. The computer processes information as electrical signals, but humans cannot understand electrical signals. The monitor changes these signals into images we can see and understand.
How Monitors Work
Inside the computer, the graphics card sends video signals to the monitor through a cable. These signals contain instructions about what to display. The monitor receives these signals and uses tiny dots called pixels to create images. Each pixel can show different colours by mixing red, green, and blue light in various amounts.
Modern monitors use millions of pixels arranged in rows and columns. When you watch a video on YouTube or type in Microsoft Word, millions of these pixels work together to create the images you see. The more pixels a monitor has, the sharper and clearer the picture appears.
Types of Monitors Based on Display Technology
1. CRT Monitors (Cathode Ray Tube)
CRT monitors were the first type of computer monitors. They look like old television sets with a bulky back. Inside the monitor, an electron gun shoots beams at a fluorescent screen to create images. These monitors were common in Nigerian schools and cyber cafes from the 1980s to early 2000s.
Advantages: CRT monitors were cheap and showed accurate colours. They worked well for graphic design. They also had no delay when displaying fast-moving images.
Disadvantages: They were very heavy and used a lot of electricity. They took up much desk space and produced heat. The screens were curved, not flat. They are now outdated and hard to find in Nigerian markets.
2. LCD Monitors (Liquid Crystal Display)
LCD monitors use liquid crystals and a backlight to create images. They are flat and thin, unlike CRT monitors. Most schools, offices, and homes in Nigeria now use LCD monitors. They became popular around 2005 to 2010.
Advantages: LCD monitors are lightweight and use less electricity than CRT. They produce less heat and take up less desk space. They have flat screens that reduce eye strain. They are affordable and widely available in Computer Village, Lagos and other Nigerian tech markets.
Disadvantages: Viewing angles can be limited – colours may change when you look from the side. Response time is slower than CRT, which can cause blur in fast video games. The backlight can fail over time, making the screen dim.
3. LED Monitors (Light-Emitting Diode)
LED monitors are actually LCD monitors that use LED lights instead of fluorescent tubes for backlighting. They are the most common type in Nigeria today. When you buy a “monitor” at any computer shop in Nigeria, you are likely getting an LED monitor.
Advantages: LED monitors use even less power than regular LCD monitors. They are thinner and lighter. The LED backlight lasts longer than fluorescent backlight. They produce brighter, more vivid colours. They are environmentally friendly because they contain no mercury.
Disadvantages: They cost more than regular LCD monitors. Cheaper LED monitors may have uneven backlighting (some areas appear brighter). When LEDs fail, replacing them can be expensive.
4. OLED Monitors (Organic Light-Emitting Diode)
OLED monitors are the newest technology. Each pixel produces its own light, so no backlight is needed. These monitors are rare in Nigeria and very expensive. You might see them in high-end electronics shops in Lagos or Abuja.
Advantages: OLED monitors show perfect black colours because pixels can turn completely off. They have excellent colour accuracy and wide viewing angles. They are very thin and flexible. Response time is extremely fast.
Disadvantages: They are very expensive. OLED pixels can “burn in” if the same image stays on screen too long. They have shorter lifespan than LED monitors. Limited availability in Nigerian markets.
Types of Monitors Based on Colour Display
1. Monochrome Monitors
Monochrome means “one colour”. These monitors display only one colour against a black background. Common colours were green, amber (orange), or white. Old computers in Nigerian government offices in the 1990s often used green monochrome monitors.
Characteristics: They provided excellent text display with sharp letters. They used very little electricity. They were cheap to buy and maintain. Good for typing and simple data entry. Cannot display pictures, videos, or coloured graphics.
2. Colour Graphics Adapter (CGA) Monitors
CGA monitors were early colour monitors from the 1980s. They could display up to 16 colours at low resolution (320×200 pixels). The quality was poor compared to modern standards.
Characteristics: They could show basic graphics and colours. Resolution was very low, making images look blocky. Limited colour palette of only 16 colours. Text was harder to read than on monochrome monitors. Suitable only for simple games and basic graphics.
3. Video Graphics Array (VGA) Monitors
VGA monitors improved on CGA with 256 colours and higher resolution (640×480 pixels). They became standard in the 1990s. Many old computers in Nigerian schools still use VGA connections.
Characteristics: Much better image quality than CGA. Could display 256 colours simultaneously. Standard resolution of 640×480 pixels. Good for office work and simple graphics. The VGA cable (blue 15-pin connector) is still used today.
4. Super Video Graphics Array (SVGA) Monitors
SVGA monitors were a major improvement, supporting millions of colours and higher resolutions. Modern monitors are all SVGA-compatible or better.
Characteristics: Display resolutions from 800×600 up to 1920×1080 (Full HD) and beyond. Support for 16 million colours (24-bit colour depth). Photo-quality images with detailed graphics. Excellent for watching videos, graphic design, and gaming. Standard for all modern computers.
Monitor Specifications You Should Know
| Specification | What It Means | Common Values |
|---|---|---|
| Resolution | Number of pixels on screen (width × height) | 1366×768 (HD), 1920×1080 (Full HD), 2560×1440 (2K), 3840×2160 (4K) |
| Refresh Rate | How many times per second the screen updates | 60Hz (standard), 75Hz, 120Hz, 144Hz (gaming) |
| Response Time | How quickly pixels change colour (measured in milliseconds) | 1ms (fast, for gaming), 5ms (normal), 10ms (slow) |
| Screen Size | Diagonal measurement of screen in inches | 19″, 21″, 24″, 27″, 32″ |
| Aspect Ratio | Ratio of width to height | 16:9 (widescreen), 16:10, 4:3 (old square monitors) |
| Brightness | How bright the screen can get (measured in cd/m²) | 250-350 cd/m² (typical), 400+ cd/m² (bright) |
| Contrast Ratio | Difference between darkest black and brightest white | 1000:1 (standard), 3000:1 (good), 100,000:1 (OLED) |
Monitor Connectors and Cables
VGA (Video Graphics Array): Blue connector with 15 pins arranged in three rows. Carries analog signals. Common on older monitors and projectors in Nigerian schools. Maximum resolution typically 1920×1080 but image quality decreases at high resolutions.
DVI (Digital Visual Interface): White connector with many pins. Carries digital signals for clearer images. Less common in Nigeria now, being replaced by HDMI. Comes in DVI-D (digital only) and DVI-I (digital and analog) versions.
HDMI (High-Definition Multimedia Interface): Small rectangular connector. Carries both video and audio signals. Most common on new monitors, TVs, and laptops sold in Nigeria. Supports Full HD, 4K, and even 8K resolution. Version HDMI 2.0 and above support high refresh rates.
DisplayPort: Similar to HDMI but with one beveled corner. Preferred for gaming monitors and high-refresh-rate displays. Can connect multiple monitors using one cable (daisy-chaining). Less common than HDMI in Nigerian markets but increasingly available.
USB-C: Small oval connector found on new laptops. Can carry video, audio, data, and power through one cable. Becoming more common on modern monitors. Convenient for connecting MacBooks and new Windows laptops.
Common WAEC/NECO Exam Mistakes
- Confusing monitor types: Students write that LED monitors are completely different from LCD monitors. Remember, LED monitors ARE LCD monitors with LED backlighting.
- Wrong resolution values: Students confuse screen size (measured in inches) with resolution (measured in pixels). A 24-inch monitor can have different resolutions like 1920×1080 or 2560×1440.
- Listing instead of explaining: When asked to “explain characteristics”, students just write “good text display” without saying WHY or HOW. Always explain what the characteristic means and give an example.
- Confusing VDU with CPU: Some students think VDU (Visual Display Unit) is the computer’s brain. The CPU is the brain; VDU is just another name for monitor.
- Wrong cable descriptions: Students describe VGA as digital when it is analog. HDMI and DVI are digital; VGA is analog.
- Forgetting Nigerian context: When giving examples, use Nigerian examples (Computer Village, cyber cafes, WAEC CBT centers) instead of foreign examples.
Practice Questions
Multiple Choice Questions
- Which of the following is NOT an advantage of LCD monitors over CRT monitors?
- a) They are lighter in weight
- b) They use less electricity
- c) They have faster response time ✓
- d) They take up less desk space
Answer: C. CRT monitors actually have faster response time than LCD monitors. LCD monitors are better in weight, power consumption, and space, but CRT was faster at changing images.
- A monitor that can display 16 million colours at a resolution of 1024×768 is classified as:
- a) Monochrome monitor
- b) CGA monitor
- c) VGA monitor
- d) SVGA monitor ✓
Answer: D. SVGA monitors support millions of colours and resolutions higher than 640×480. This specification describes SVGA capability.
- Which connector carries both video and audio signals?
- a) VGA
- b) HDMI ✓
- c) DVI
- d) All of the above
Answer: B. HDMI carries both video and audio through one cable. VGA carries only video (analog), DVI carries only video (digital). You need separate audio cables with VGA and DVI.
- The smallest unit that makes up a monitor’s display is called:
- a) Byte
- b) Pixel ✓
- c) Bit
- d) Character
Answer: B. A pixel (picture element) is the smallest dot on a screen. Millions of pixels work together to create the images you see on a monitor.
Essay/Theory Questions
- State FIVE differences between CRT monitors and LCD monitors. (10 marks)
Mark allocation: 2 marks per difference, must state both sides clearly
Examiner’s tip: Use a comparison format. For each point, say what CRT does AND what LCD does differently. Example: “CRT monitors are bulky and heavy while LCD monitors are thin and lightweight.”
- Explain FOUR factors you should consider when buying a monitor for graphic design work. (8 marks)
Mark allocation: 2 marks per factor (1 mark for naming, 1 mark for explanation)
Examiner’s tip: Don’t just list “resolution, size, colour”. Explain WHY each factor matters for graphic design specifically. Example: “High resolution (at least 1920×1080) is important because designers need to see fine details in images and work with multiple windows.”
- (a) What is a Visual Display Unit (VDU)? (2 marks)
(b) Describe THREE types of monitors based on colour display. (9 marks)
(c) State TWO advantages of LED monitors over LCD monitors. (4 marks)Total: 15 marks
Examiner’s tip: For part (b), “describe” means give details about characteristics, not just names. For each monitor type, mention colour capability, resolution, and at least one use. Part (c) asks to “state” so brief points are acceptable, but still give complete sentences.
Memory Aids
Monitor Technology Evolution (Chronological):
C-L-L-O = CRT → LCD → LED → OLED
(Like saying “See Leo” – helps remember the order monitors developed)
VGA Cable Colour:
VGA = Very Good Analogue = BLUE connector
(VGA cables are always blue in Nigerian computer shops)
Resolution Levels:
HD-FH-2K-4K = HD (1366×768) → Full HD (1920×1080) → 2K (2560×1440) → 4K (3840×2160)
(Each roughly doubles the pixel count)
HDMI vs DisplayPort:
H-D = Home-Display
HDMI for Home entertainment (TVs, general use)
DisplayPort for Display professionals (gaming, design)
(Both work for everything, but this shows common usage)
Related Topics
- Input and Output Devices: Learn about other output devices like printers and speakers, and input devices like keyboard and mouse
- Computer Hardware Components: Understand how the graphics card sends signals to the monitor
- Storage Devices: Know where the images and videos displayed on monitors are stored
- Computer Software: Learn about graphics software that creates the images shown on monitors
- Digital and Analog Signals: Understand the difference between VGA (analog) and HDMI/DVI (digital) signals