title: What is the difference between mapped region and unmapped region in memory space?
body: <p>I came across the following paragraph in <a href="http://www.learnme.in/malloc-c/" rel="noreferrer">an article about malloc</a>.</p>
  
  <blockquote>
    <p>The heap is a continuous (in term of virtual addresses) space of
    memory with three bounds:a starting point, a maximum limit (managed
    through sys/ressource.h’s functions getrlimit(2) and setrlimit(2)) and
    an end point called the break. The break marks the end of the mapped
    memory space, that is, the part of the virtual address space that has
    correspondence into real memory.</p>
    
    <p><a href="https://i.stack.imgur.com/DrW9C.png" rel="noreferrer"><img src="https://i.stack.imgur.com/DrW9C.png" alt="enter image description here"></a></p>
  </blockquote>
  
  <p>I would like to better understand the concept of mapped region and unmapped region.</p>