.data
00000000 X dd ?
00000004 Y dd 8
00000008 B dd 3
0000000C A dd 2
00000010 Highest dd ?
.code
Main Proc Near ;; int Max( int Q, int R) {
Push offset B ;; X=Max(A, B)
Push offset A
Call Max
Add eSp, 8 ;; Remove A and B
Mov X, eAx
Push offset Y ;; Highest=Max(X,Y)
Push offset X
Call Max
Add eSp, 8 ;; Remove X and Y
Mov Highest, eAx
Call PutDec
Push 0 ;; Stop
Call ExitProcess
Main Endp
|
;; int Max( int &Q, int &R)
;; - Find maximum of two int references
;; Arguments - Q, R int reference
;; Returns - eAx contains maximum Q & R on return
;; Registers Altered - eAx, eBx, eSi
Max Proc Near ;; Note Near procedure
Push eBp ;; Save Caller's Frame Ptr
Mov eBp, eSp ;; New Frame Ptr for Max
;; ___________ Assuming that the call was
;; | | Z = Max( A, B ); the stack
;; |___________| appears at left after the
;; R |&B=00000008| <- eBp+12 instruction sequence:
;; |___________|
;; Q |&A=0000000C| <- eBp+8 Push eBp
;; |___________| Mov eBp, eSp
;; |Return Addr| <- eBp+4
;; |___________|
;; | Old eBp | <- eBp = eSp
;; |___________|
;; {
Mov eBx, [eBp+12]
Mov eAx, [eBx]
Ifa: Mov eSi, [eBp+8]
Cmp [eSi], eAx ;; if (Q > R)
Jg Thena
Jmp Elsea
Thena: Mov eAx, [eSi] ;; eAx = Q;
Jmp EndIfa
Elsea: Mov eAx, [eBx] ;; else eAx = R;
EndIfa: ;; }
Pop eBp ;; Restore Frame Pointer
Ret ;; Return maximum in eAx
Max Endp
End Main
|
to assembly language and the machine's architecture. C++ and Pascal support
indirection using pointer variables that 1) hold an address that references
2) a variable, hence the indirection. The Intel processor uses registers (Bx, Si, Di, and Bp
for 16-bit or any 32-bit) as pointers, these registers can hold an
address used for the indirection. The following three examples are identical
with variables i, an integer, and bx, a pointer to an integer.
In the diagram at right, BX holds the address of variable i.
