Input & Output (<kbd>, <samp>, <output>)

When To Use 

• The <kbd> element denotes user input like keyboard buttons ("Ctrl + C") or voice commands. ¹
• The <samp> element in HTML is used to contain text that represents sample or quoted output from a computer program. ²
• The <output> element is used to represent an output of a calculation by the website. ⁴

Rules

• These <dbd> and <samp> elements does not seem to have any impact on assistive technologies. Therefore you may use them if you see fit, but they will not impact the accessibility of your website.
• The <output> element is meant for dynamic calculations in contrast to the <samp> element which only represents static output. ⁴
• The <output> element is often times implemented by user agents as a aria-live region. This means that changes inside the element are automatically announced by screen readers. ³

Sources 

1. MDN: <kbd>: The Keyboard Input element by Mozilla contributors is licensed under CC-BY-SA 2.5
2. MDN: <samp>: The Sample Output element by Mozilla contributors is licensed under CC-BY-SA 2.5
3. MDN: <output>: The Output element by Mozilla contributors is licensed under CC-BY-SA 2.5
4. HTML Spec: 4.10.12 The output element is licensed under Creative Commons Attribution 4.0 International License