Bài giảng tin học đại cương C++ (chương 5)

CHNG5:TRUYCPTRCTIPB  §1.CÁCHÀMTRUYCPTHEOĐACHPHÂNĐON 1.Hàmpokeb():Dùnggimtkítvaluevàobnhtiđachphânđon off.Nguyênmucahàmtrongdos.hlà:  voidpokeb(unsignedseg,unsignedoff, charvalue)  2.Hàmpeekb():Nhnmtbytetichseg:off.Nguyênmucahàmtrong dos.hlà:  charpeekb(unsignedseg,unsignedoff)  3.Hàmpoke():Gimtsnguyênvaluevàobtiđachseg:off.Nguyên muc ahàmtrongdos.hlà:  voidpoke(unsignedseg,unsignedoff,intvalue)  4.Hàmpeek():Nhnmtwordtiđachseg:off.Nguyênmuhàmtrong dos.hlà:  voidpeek(unsignedseg,unsignedoff)  5. Hàm movedata(): Sao n byte tiđa ch seg_gui:off_guiđ nđa ch seg_nhan:off_nhan.Nguyênmucahàmtrongmenu.hlà:  void movedata(unsigned seg_gui,unsigned off_gui, unsigned seg_nhan,unsignedoff_nhan,intn)  §1.ĐITĐACHPHÂNĐONSANGĐACHTHC 1.Đitđachthc:Đitđichthc sangđachphânđontadùng macrosau:  unsignedFP_SEG(diachithuc) unsignedFP_OFF(diachithuc)  2.Đitđachphânđon:Đitđachphânđonsangmacro:  voidfar*MK_FP(seg:off) Víd:Saukhithchincáccâu lnh: charbuf[100]  unsignedds,dx;  ds=FP_SEG(buf)  dx=FP_OFF(buf) thìds:dxchađachcamngbuf.  Saukhithchincâulnh: 51  char*pchar;  pchar=(char*)MK_FP(0xb800:0) thìpchartrtibnhmànhình.Khiđótacóthdùngcáclnhđtruy cptibnhmànhình.  Chngtrình51:Lpchngtrìnhxácđnhđachc amtngt. #include<dos.h> #include<conio.h> #include<stdio.h> voidmain() { unsignedcharfar*p; intn,k; unsignedseg,off; clrscr(); p=(unsignedcharfar*)MK_FP(0,0); while(1) {  printf(\nSohieungat(Bam0deketthuc):);  scanf(%d,&n);  if(n==0) break;  k=(n 1)*4;  off=p[k]+256*p[k+1];  seg=p[k+2]+256*p[k+3];  printf(\nDiachicuangat%x:%x,seg,off); } }   Shiucamingtđcđánhst0nhngnđcnhpt1,mi ngtchim4bytenên:  k= (n1)*4;    52