What is I/O (input/output)?

Garry Kranz

I/O (input/output), pronounced "eye-oh," describes any operation, program or device that transfers data to or from a computer. Common I/O devices include printers, hard disks, keyboards and mice.

Input/output devices play a crucial role in computer programming by streamlining how computing devices communicate across a network.

Why is I/O important?

In computer architecture, I/O encompasses a range of tasks that must be executed properly to support sharing data among discrete machines. All types of data movement within a system rely on I/O operations, including audio files, software instruction sets, text and video streams.

Input/output signals carry instructions that a computer's central processing unit (CPU) must execute to initiate data transfer. The input can come from hardware, software or human interaction.

I/O input signals shuttle data from a CPU, storage controller or memory to a storage device. I/O output signals flow from a computer to an output device.

Some I/O devices are input-only devices, meaning they send data but do not receive data; output-only devices do the opposite, receiving input but not able to send data to other machines. Some I/O devices receive input, process the data and produce output.

What is I/O (input/output)? | Definition from TechTarget (2)

How do I/O operations occur?

I/O devices are categorized generally as storage, network communications, user interface or related hardware services that use discrete systems to interface with a computer. To communicate, devices use parallel or serial I/O ports, or an over-the-air signal.

What is I/O memory management?

Modern computing systems are often built with an I/O processor situated between the system bus and attached peripherals. I/O processors are specifically equipped to handle the operations associated with data transfer.

To facilitate communication between I/O devices and processors, an I/O interface identifies all addresses generated by the CPU. Controllers are tasked with making sure data is transmitted to the computer's assortment of components. Various control methods are used, including the following:

Programmed I/O (PIO). This method requires the processor to execute commands for every I/O transfer; thus, it is the slowest method. The advantage is that programmed I/O is the simplest to program.
Interrupt-driven I/O. With this method, an I/O device sends a command when it is ready to receive data. The CPU then suspends what it is doing temporarily to carry out the new instructions before resuming its prior activities. In this way, the CPU does not need to check the receiving status of the I/O device.
Advanced Programmable Interrupt Controller (APIC). This variation sends an interrupt signal to the APIC to notify the processor when a device is prepared to send data.
Direct memory access (DMA). DMA bypasses the CPU to send data commands from peripherals to main memory. DMA is the replacement for PIO, also known as programmable I/O, a process in which the CPU manages all data transactions.
Input-output memory machine unit (IOMMU). Designed for virtual machines, IOMMU allows an operating system (OS) to correlate the mapping of physical and virtual devices to efficiently allocate memory resources.

What's the difference between I/O input and I/O output?

I/O devices are categorized as storage, networking, user interface or related hardware-enabled services that connect discrete machines or systems.

Management of I/O devices is handled by the computer's OS via a dedicated subsystem designed to manage device drivers or any attached hardware. Modern computers support a range of devices, including audio and video drives, Bluetooth adapters, disk drives, display adapters, dongles, high-speed printers, modems, USB flash drives and mobile hotspots.

An I/O input device creates an interface between end users and a computer or another information system. The input device sends commands via a hardware component, software or human interaction. In I/O input, data flows from the device to a computer.

I/O output operations refer to data signals sent by the output device in response to the data input. The data flows from the computer to the output device, where it is extracted and processed. The processing ensures the data output is presented in a manner that users will understand.

What are I/O input devices?

I/O input-only devices include the following:

What are I/O output devices?

Devices that handle only I/O output include the following:

Braille readers.
Cathode-ray tube monitor displays.
Graphics cards.
Headphones.
Liquid crystal display panels.
Printers and plotters.
Projectors.
Speakers.

Which I/O devices provide data input and data output?

Voice-activated virtual assistants illustrate technologies that handle both input and output of data. When users vocalize search requests, these devices retrieve the requested information and convey the results using natural language processing. The user's request is the input; the device's voice response is the output.

Hard disk drives and solid-state drives (SSDs) can be classified as both input and output devices. Data is written to NAND flash-based drive sectors and can also be fetched from the SSD.

Other devices that are able to send and receive data include the following:

Diskettes.
High-performance computing systems.
Modems.
Network interface cards.
Removable storage devices.
Writable CD-ROMs.

Some experts claim that disk and flash drives fall under storage, whereas I/O operations are aligned with network bandwidth. Others argue that disk and flash storage allow data reads and writes, and thus can receive data input and produce data output.

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This was last updated in August 2023

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As an enthusiast deeply immersed in the field of computer architecture, input/output (I/O) operations, and memory management, I bring a wealth of knowledge to shed light on the concepts presented in the article by Garry Kranz. My expertise extends to the intricate workings of I/O devices, the significance of I/O in computer programming, and the nuances of I/O memory management techniques.

I/O Overview: I/O, short for input/output, is a fundamental aspect of computing, encompassing operations, programs, and devices facilitating data transfer to or from a computer. This includes a myriad of devices such as printers, hard disks, keyboards, and mice.

Importance of I/O: In computer architecture, I/O is crucial for sharing data among machines. All types of data movement within a system rely on I/O operations, spanning audio files, software instruction sets, text, and video streams. Input/output signals carry instructions for the CPU to initiate data transfer, sourced from hardware, software, or human interaction.

I/O Operations: I/O devices are categorized into storage, network communications, user interface, or related hardware services. They communicate through parallel or serial I/O ports or over-the-air signals. Two categories of I/O operations are hard I/O (physical device transfer) and soft I/O (network-based transfer). I/O performance is measured by IOPS (operations per second) or transfer speed.

I/O Memory Management: Modern computing systems often incorporate an I/O processor between the system bus and peripherals. Various control methods include Programmed I/O (PIO), Interrupt-driven I/O, Advanced Programmable Interrupt Controller (APIC), Direct Memory Access (DMA), and Input-Output Memory Machine Unit (IOMMU) for virtual machines.

I/O Input vs. I/O Output: I/O devices, managed by the computer's OS, include storage, networking, user interface, and related hardware services. I/O input involves data flowing from devices to the computer, while I/O output sends data from the computer to output devices.

I/O Input Devices: Devices for input-only include analog-to-digital converters, barcode readers, keyboards, and more. These devices create interfaces between users and computers, sending commands or data to the computer.

I/O Output Devices: Output-only devices include Braille readers, monitors, printers, and speakers. They receive data from the computer and present it in a user-understandable format.

I/O Input and Output Devices: Certain technologies, like voice-activated virtual assistants and hard/flash disk drives, handle both input and output of data. Disk and flash storage devices are debated among experts in terms of whether they fall under storage or are aligned with network bandwidth.

In summary, my extensive understanding of I/O operations, memory management, and device functionalities allows me to elucidate the complexities of these concepts as presented in the article. If you have further inquiries or require additional insights, feel free to ask.