New Folder/4GB.C

#include
#include
void Set4gb();
void openA20();
void main()
{
 unsigned long addr;
 openA20();
 Set4gb();
 asm push ds
 asm mov ax,0
 asm mov ds,ax
 asm mov esi,00100000h
N1: asm mov eax,[esi]
 asm mov dword ptr[esi],0
 asm mov ebx,[esi]
 asm mov dword ptr[esi],0ffffffffh
 asm mov ecx,[esi]
 asm mov [esi],eax
 asm inc ecx
 asm cmp ebx,ecx
 asm jne N2
 asm add esi,4
 asm jmp N1
N2: asm mov addr,esi
 asm pop ds
 printf("RAM=%1d(Mb)",addr>>20);
}
void openA20()
{
 while(inp(0x64)&2);
 outp(0x64,0xd1);
 while(inp(0x64)&2);
 outp(0x60,0xdf);
 while(inp(0x64)&2);
 outp(0x64,0xff);
}
void Set4gb()
{
 asm cli
 asm push ds
 asm push es
 asm mov dword ptr GDT_Addr[0],(2*8-1)
 asm mov eax,ds
 asm shl eax,4
 asm xor ebx,ebx
 asm  mov bx,offset GDT_def
 asm add eax,ebx
 asm mov dword ptr GDT_Addr[2],eax
 asm lgdt fword ptr GDT_Addr
 asm mov bx,8
 asm mov eax,cr0
 asm or al,1
 asm mov cr0,eax
 asm jmp flush1
flush1:
 asm mov ds,bx
 asm mov es,bx
 asm and al,0feh
 asm mov cr0,eax
 asm jmp flush2
flush2:
 asm pop es
 asm pop ds
 asm sti
}