title: Which library/code is responsible for rendering the terminal in retro computers?
body: <p>For example as you type, which library is telling the computer screen to display the respective ascii character and to move the cursor accordingly?</p>
  
  <p>Imagine something like the old school computers (with no GUI) running DOS or Basic... what/which library is responsible for the UI?</p>
  
  <p>Links to source code would be great for understanding how said library(ies) works.</p>
  
  <p><a href="https://i.stack.imgur.com/VZApc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VZApc.png" alt="enter image description here"></a></p>