title: Global Descriptor Table
body: <p>I've been reading Intel manual about Virtual Memory (Segmentation + Paging). As I understand there is special register that holds Global Descriptor Table (GDT). GDT contains NULL Descriptor, Local Descriptor Table, TSS, and Segment Descriptor. Also almost all Operating Systems (OS) has one GDT and that gets loaded during boot time and cannot be changed (Maybe!!!). My questions are:</p>
  
  <ol>
  <li>Where all of those information stored (NULL, LDT, TSS, and Segment Descriptor)? Are they in Physical Memory, RAM or Local Hard Drive?</li>
  <li>Are Segment Descriptors the same as Code Segment (ASM: CS), Data Segment (ASM: DS), ... and if so how many of those are stored in  GDT (Is there only one CS, one DS, ...)?</li>
  <li>Does Protable Executable (PE) Loader manipulate any of these information?</li>
  </ol>