CODEWITHSUNDEEP
memory-managementx86-16biosreal-modembr
Nerios
Nerios

Reputation: 33

memory allocation in real mode in the MBR

In a MBR, the following code in the preboot environment allocates a buffer of 10Kb by subtracting 10h from the total amount available :

seg000:7C1D sub word ptr ds:413h, 10h

seg000:7C22 mov ax, ds:413h

seg000:7C25 shl ax, 6

seg000:7C28 mov ds:buffer_segm, ax

I don't understand where exactly does the 10KB allocation come from

I just understand that in the preboot environment, there is no memory manager then the BIOS maintains the number of kilobytes of available memory in a 16-bit value at the address 0:413h. It's mainly the 2nd and 3rd lines that I don't understand, that is 10Lb allocation ? how ? at which address XXXX:YYYY in real mode ?

Upvotes: 1

Views: 127

Answers (0)

Related Questions