Output Devices

Hello students, welcome to Kwickprep. A computer can calculate a million results, but what use are they if we cannot see, hear or hold them? That is the job of output devices. Today we will learn about screens, projectors, printers, speakers and even motors that move things.

First, the meaning. An output device takes the processed results out of the computer. It turns binary signals, the zeros and ones, into pictures, sound, paper or movement. A soft copy is output you see or hear, like a result on the screen. A hard copy is permanent physical output, like a printed marksheet.

Output devices are grouped by the kind of output. Visual output appears on a monitor or a projector. Printed output comes from a printer, like a school fee receipt. Sound comes out of speakers and headphones. And movement comes from actuators, like the motor in a robot arm.

The monitor is the most common output device. It is also called a display or a screen. Every picture on it is made of tiny dots called pixels. Resolution is the number of pixels across and down, like nineteen twenty by ten eighty, and more pixels give a sharper picture. Most monitors are L C D screens lit by L E Ds. Many phones use O L E D, where each pixel makes its own light.

Next, the projector. A projector shows the computer's output on a large wall or white screen. It is useful when many people must see at once, like in classrooms, meetings and cinema halls. Its brightness is measured in lumens, and a brighter projector works better in a room with light.

Now, printers, starting with inkjet. An inkjet printer sprays tiny drops of liquid ink through very small nozzles onto the paper. It is best for colour photos and home printing. The printer itself is cheap to buy. But the ink cartridges are costly, so each page costs more.

A laser printer works in a different way. A laser draws the page as static charge on a drum, powder called toner sticks to it, and heat fuses the toner onto paper. It is best for printing fast text quickly, as in offices and schools. The printer costs more to buy. But the cost per page is low, because toner lasts a long time.

A three D printer makes a real solid object, not a picture. First, the object is designed as a three dimensional model on a computer. Then the printer melts plastic thread and builds the object one thin layer at a time. This is called additive manufacturing, and it is used for models, spare parts and even medical implants.

Pause and predict for two cases. A school prints five hundred black and white notices every week. A family prints a few colour photos each month. Which printer suits each one? The school needs a laser printer, because it is fast and cheap per page. The family is happy with an inkjet, because it prints good colour and costs less to buy.

Now, sound output. Speakers turn electrical signals into sound waves that we hear. The computer stores sound as digital numbers, so a sound card first converts it to an analogue signal, a smooth wave. Headphones do the same job, but only one person can hear.

The last output device makes things move. An actuator is an output device that turns a signal from the computer into physical action. Motors, pumps, valves and buzzers are all actuators. They are often part of a control system, where a sensor gives input and the actuator gives output. We find them in robots, smart homes and automatic farm systems.

Here is an automatic plant watering system. First, a moisture sensor reads how wet the soil is. The computer asks, is the soil too dry? If yes, it sends a signal to turn the pump motor on. If no, the pump motor stays off. Then it waits and checks again.

Let us revise what we learned today. Output devices bring the results out of the computer. Monitors and projectors give visual output made of pixels. Inkjet, laser and three D printers give hard copy output. Speakers give sound, and actuators give movement. Find one actuator in your home today, and name the sensor that controls it.