Chapter 40 Flashcards Preview

Computer Architecture and Assembly Language Programming > Chapter 40 > Flashcards

Flashcards in Chapter 40 Deck (9)
Loading flashcards...
1
Q

What is GDT

A

GDT is an array-formatted table of descriptors where each descriptor is an 8byte entry

2
Q

What is GDTR

A

The base and limit of GDT is stored in a 48bit register called the GDTR

3
Q

What is LGDT

A

It’s a special instruction of GDTR register

4
Q

What is null descriptor

A

The first entry of the GDT must always be zero. It is called the null descriptor.

5
Q

What is limit of GDT

A

8191 + null descriptor

6
Q

Which bit defines the limit of GDT

A

G

7
Q

What is DPL

A

descriptor privilege level

8
Q

What is role of B (big) bit

A

B (big) bit tells that if this data segment is used as stack SP or ESP.

9
Q

What is Gate A20

A

Its a work around in which, BIOS call will simply enable it to open the whole memory for us.