Is a monitor an input or output device?

If you plan on becoming a software developer it’s important to understand whether a computer monitor is an input or an output device. With the introduction of touchscreen computer monitors, it can be difficult to understand what type of device you are actually using.

A computer monitor is an output device because it receives information from a computer’s central processing unit but doesn’t ever send information back to it. Input devices on the other hand send information to the central processing unit but do not receive any information. 

There are obviously exceptions to the above, such as touchscreen monitors, that we will explore later in this article. 

Let’s take a closer look at why a monitor is an input device and not an output device.

Is a monitor an input device?

A computer monitor Is not an input device, it is actually an output device. A computer monitor is an output device because your computer sends information to it rather than receiving information from it.

As you can see from the diagram below a computer processor sends instructions and data to an output device.  A printer is another output device that receives information from the central processing unit. It is sent electronic information which it then converts into physical copies by printing the information on paper.

Output device data flow

In the case of a computer monitor, it is sent data that it then outputs in visual form. The data it is sent can range from movies on Netflix, to simply displaying the clicking and opening a folder. 

A simple way to remember that a monitor is an output device is to just think of how the data flows. A joystick or a mouse sends your computer information. However, your computer monitor only ever receives data from the processing unit. As a user, you don’t have to do anything for your monitor to begin outputting information.  On the other hand, if you don’t move your mouse or joystick, nothing will happen.

Let’s break down the typical flow of information to your monitor.

You will likely open your laptop or move your mouse, then the mouse will send information to the processor as a set of instructions. These instructions tell the computer that you want it to wake up so you can use it. The processor then sends information to relevant output and storage devices. In this case, it would require the hard drive to start and the computer monitor to turn on. As a user, you receive this feedback via the display turning on and showing your desktop

Why a monitor is an output device 

A computer monitor is an output device because it takes information from the computer processor and then outputs something visual. A computer monitor will only ever receive information from your computer, it does not send information back to the processor as a set of instructions to be handled.

 The diagram below shows the data flow between an input device like a mouse and your computer. As you can see an input device sends your computer a set of instructions that it needs to process. In the case of a mouse, it tracks your movement and then updates your computer with this information. It then decodes this information. From here the computer updates your monitor with this information which you see by a change in position of the cursor.

Input device data flow

Your monitor’s job as an output device is to process the information it receives from your computer. Its purpose is not to send information to your computer, this is the job of an input device like a keyboard

As well as input and output devices your computer also has storage devices like a hard drive. However, as an output device, all your monitor has to do is to correctly display the files that are held on a hard drive.

In short, a computer monitor is an output device because:

  • It only receives data from the processor.
  • It doesn’t send information to the processor.
  • Changes to your monitor do not directly impact your computer or other input devices.
  • It decodes data and represents it visually

Is a touchscreen monitor an input or output device?

A touchscreen monitor is both an input device and an output device. The touch element of the monitor is the input and the display element of the monitor is the output. Touchscreen monitors are becoming increasingly popular and the market is set to be worth $100 billion by 2027.

A touchscreen monitor effectively combines three different devices: a keyboard, a mouse, and a monitor. However, most touchscreen monitors are split into two distinct parts you have the touch layer and the display layer. The touch layer Captures your movements either via a pen or your fingers. like a typical monitor, which is an output device, the display element of a touchscreen monitor outputs things visually

Computer data flow

Using the diagram below as reference we can begin to explain how a touchscreen monitor works. The contact layer of the screen picks up your finger movement and acts as an input device and then sends this information to your computer’s processor. From here the instructions are computed and then output via the touchscreen monitor’s display element.

A touch screen monitor effectively has two different devices working as one, which is how it can both send and receive data from the processor. A normal monitor is not able to do this because it does not have a touch layer to capture your finger movement as an input.

It is correct to say that a touchscreen monitor is both an input and an output device. However as explained in the breakdown above, when we dive a little deeper it is two distinct elements of a touch screen monitor that allow it to act in this way

Can a monitor be used as an input device?

A typical LCD or CRT monitor cannot be used as an input device. However, a touchscreen monitor can be used as an input and an output device. A standard computer monitor does not have a touch or input layer to act as an input device, therefore it can only ever be used as an output device.

The two most common types of monitor are liquid crystal display (LCD)  play and cathode ray tube (CRT). These monitors do not come with a touch panel and standard, that is why a monitor can not be used as an input device.

However, advances in technology have changed things slightly.

In modern smartphones and monitors, a touch panel sits over the top of the display and is responsible for recording the touches of a user and sending them to the computer. It is unlikely that you will ever find a touchscreen cathode ray tube monitor. Newer touchscreen monitors all have LCD or  OLED screens.

It is these touch panels that allow a monitor to act as both an input and an output device. Without a touch panel, a monitor can never be used as an input device, only as an output device.

Conclusion

A monitor is an output device because it typically only ever receives data from your computer and then outputs it. Unlike input devices which send data to your computer’s process to be decoded and sent to other parts of the system.

Typical monitors only ever act as output devices to display your favorite movies and computer software. However, touch screen monitors are both input and output devices. Their touch panels act as inputs that track your finger movements, while the LCD or OLED screen act as a traditional output device.

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