1. IP high IP low IP high IP low BP high BP low IP high IP low BP high BP low FL high FL low CS high CS low IP high IP low _TEXTsegment byte public ‘CODE’ ;main() assume cs:_TEXT _mainproc near push bp mov bp,sp ;{ ; asm mov dl,0x30/* begin counter at ‘0’ */ mov dl,30h ; asm mov ah,2/* display character function */ mov ah,2 ; next: @1@86: ; asm int 0x21/* DOS call */ int 21h ; asm inc dl/* increment counter */ inc dl ; asm cmp dl,0x3a/* is counter > ‘9’ ? */ cmp dl,3ah ; asm jnz next jne short @1@86 ;} mov sp,bp pop bp ret _main endp _TEXT ends end main() { asm mov dl,0x30/* begin counter at ‘0’ */ asm mov ah,2/* display character function */ next: asm int 0x21/* DOS call */ asm inc dl/* increment counter */ asm cmp dl,0x3a/* is counter > ‘9’ ? */ asm jnz next } 8.12 Interfacing C with Assembly Language SP when entering _main  014E 014D 014C 014B 014A 0149 0148 0147 0146 0145 0144 0143 0142... Stack area (highest address up), offset address (SS value not shown) and content: TCC -S FILENAME.ASM FILENAME.C written by the program calling “_main” SP value loaded in BP  written when calling INT21H and released by IRET

2. IP high IP low IP high IP low BP high BP low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low BP high BP low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low BP high BP low “c” high “c” low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low BP high BP low “c” high “c” low “c” high “c” low “s@” high “s@” low IP high IP low BP high BP low “a” high “a” low “e” high “e” low “b” high “b” low “d” high “d” low “b” high “b” low “a” high “a” low IP high IP low BP high BP low “c” high “c” low “c” high “c” low “s@” high “s@” low IP high IP low... _TEXT segment byte public ‘CODE’ ;main() assume cs:_TEXT _main proc near push bp mov bp,sp ;{ ; int a, e, b, d; sub sp,8 ; a=5; mov word prt [bp-2], 5 ; b=7; mov word prt [bp-6], 7 ; addem(a, b); push word prt [bp-6] push word prt [bp-2] call near ptr _addem pop cx ;} mov sp,bp pop bp ret _main endp ;void addem(int x, int y) assume cs:_TEXT _addemproc near push bp mov bp,sp ;{ ; int c; sub sp,2 ; c = x + y; mov ax, word prt [bp+4] add ax, word prt [bp+6] mov word prt [bp-2], ax ; printf (“The sum is %3d\n”, c); push word prt [bp-2] mov ax, offset DGROUP:s@ push ax call near ptr _printf pop cx ;} mov sp,bp pop bp ret _addem endp _TEXT ends _DATA segment word public ‘DATA’ s@label byte db ‘The sum is %3d’ db 10 db 0 _DATA ends end #include void addem(int x, int y); main() { int a, b; a=5; b=7; addem(a, b); } void addem(int x, int y) { int c; c = x + y; printf (“The sum is %3d\n”, c); } 8.12 Interfacing C with Assembly Language TCC -S addem.asm addem.c 014E 014D 014C 014B 014A 0149 0148 0147 0146 0145 0144 0143 0142 0141 0140 013F 013E 013D 013C 013B 013A 0139 0138 0137 0136 0135 0134 0132 0131... Stack area: written by the program calling “_main” BP for “_main” parameter passing to “printf” clearing parameter area after returning from “printf” parameter passing to “_addem” “_main”’s variables return address from “_addem” clearing parameter area after returning from “_addem” restoring SP and BP as before “_main” “_addem”’s BP “_addem”’s variable

3. .MODEL SMALL,C 0000.CODE PUBLIC xplusy 0000 xplusy PROC NEAR C,x:WORD,y:WORD LOCAL z:WORD 0006 8B 46 04 MOV AX,x ;load x value into AX 0009 03 46 06 ADD AX,y ;add value of y to AX 000C 89 46 FE MOV z,AX ;store AX in z RET 0013 xplusy ENDP END 2755:0020 55 PUSH BP 2755:0021 8BEC MOV BP,SP 2775:0023 83C4FE ADD SP,FE 2775:0026 8B4604 MOV AX,WORD PTR [BP+04] 2775:0029 034606 ADD AX,WORD PTR [BP+06] 2775:002C 8946FE MOV WORD PTR [BP-02],AX 2775:002F 8BE5 MOV SP,BP 2775:0031 5D POP BP 2775:0032 C3 RET #include extern int xplusy(int x,int y) main() { int a, b; a=5; b=7; printf(“The sum is %d\n”xplusy(a,b)); } 8.12 Interfacing C with Assembly Language 00 07 00 05 IP high IP low 00 07 00 05 IP high IP low BP high BP low 00 07 00 05 IP high IP low BP high BP low 00 0C SP when entering “xplusy”  014E 014D 014C 014B 014A 0149 0148 0147 0146 0145 0144 0143 0142... “b” and “a” passed by “main” SP value loaded in BP  reserved for “z” return to “main” address Linked “xplusy” Assembled “xplusy” C program calling assembler routine “xplusy” Stack area used to pass parameters to “xplusy” assembler subroutine: