Is a plotter an input or output device?

A plotter is an important peripheral device that was the go-to technology to print architectural drawings and graphics, so understanding if a plotter is an input or output device is crucial. 

A plotter is a computer output device that can print graphics, architectural designs, engineering plans, and other large designs. It receives commands from the computer and then outputs line drawings on paper using automated pens. 

They have largely been replaced by large-format inkjet printers that are able to print in intricate detail. However, they remain an important part of computing history.

Let’s explore why a plotter is an output device and the specifics of what the device actually does. 

What are input and output devices?

To better understand why a plotter is an output device and not an input device, let’s look at the difference between the two. A computer is typically made up of four parts inputs, outputs, the processor, and the storage. 

The central processing unit, or CPU, is the brain of your computer and performs complex computations. Whereas your hard drive and flash drives form the storage components of a computer and keep hold of files.

Input and output devices are different.

Input Devices

Input devices send data to the CPU. A joystick and scanner are good examples of input devices. A joystick tracks your movements and then sends this to the CPU, a scanner creates a digital copy of your documents and sends it to the processor in a digital format. 

The core function of every input device is to send data to the CPU to be actioned, whereas output devices primarily receive data then perform an action.

Output Devices

Output devices, like a monitor, receive data from the CPU which they then decode and use to output something. A monitor receives data and then outputs it in a visual format, whereas something like a plotter outputs the information it receives onto paper. 

What is a plotter?


A plotter is a large output device similar in nature to a printer that is used to print graphics, architectural plans, and other intricate designs. They were the first type of printer that could print with color and had the ability to render graphics and other big drawings. Unlike a printer, a plotter uses automated pens to print and can also output point-to-point lines.

The advancement in inkjet printing technology has nearly eliminated plotters from the market. Instead, people now use wide-format printers which are capable of producing incredibly detailed designs. However, three decades ago plotters were leaps and bounds heads of traditional printing methods and cost significantly more to make. 

Despite their waning popularity, there are still a few advantages to using plotters which include:

  • Plotters can work on large sheets of paper and still maintain high resolution.
  • They can print on a variety of different materials including plywood, sheet steel, cardboard, aluminum, and plastic.
  • Plotters allow the same pattern to be drawn thousands of times without any image degradation.

Is a plotter an input or output device?

A plotter is an output device that prints full-size graphics and complex architectural designs onto paper. It converts coordinates into plots and old-style plotters actually used to plot with individual pens. 

Plotters were able to print in color long before the household inkjet printers we have all come to love. Essentially a plotter outputs large documents using a bank of pens to create the graphic or design. 

The reason a plotter is an output device is because of the flow of information. Like other output devices, a plotter receives instructions and data from the central processor. It then outputs this data onto large-format documents. It doesn’t send information or instructions to the processor in the same way input devices like a keyboard or mouse would. 

Plotter technology has come a long way since the early pen plotters of the 1950s. Despite still sharing a namesake they are now very different devices. Gone is the rudimentary marking of single lines on a paper. Modern plotters are essentially high-end inkjet printers capable of outputting incredibly large documents. It makes them perfect for graphic design work or architectural prints. In the past, inkjet and laser technology were not advanced enough to print in enough detail, that is why plotters were so popular. The quality didn’t diminish as the size grey.

Nowadays wide-format printers are used instead of plotters but they often mistakenly go by the same name. However, plotters tend to only accept vector formats like SVG, DWG, AI, and CDR. Normal printers use BMP, PNG, PDF, JPG, and TIFF formats.

Why a plotter an output device?

plotter data flow
Plotter data flow

A plotter is an output device because instructions always flow from the computer to the plotter which outputs them as printed designs. In contrast, input devices send instructions and data to the processor which then sends them onto the right part of the system. 

Output devices like a plotter receive information and then act on it, whereas input devices track activity then send information onwards. 

Using the diagram above we can track the data flow of a plotter. A user would click a document to print using the mouse. The mouse would track these movements and clicks and then send them onto the CPU. When the relevant file has been clicked the processor would send instructions to your hard drive to retrieve the document from storage. It would then be opened and displayed on your monitor. When you click to print the document further instructions are sent to the plotter to output the document.

As you can see at no point does information flow back to the processor or any input devices from the plotter. It only ever receives instructions which it must act upon. Plenty of our devices send small communications back and forth to the CPU, even if they are output peripherals. However, for simplicity, we should always aim to categorize a component by its primary focus. In the case of a plotter, it functions as an output device that produces intricate drawings and designs.