initial checkin from subversion

integerarithmetics/intarith.asm

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+; intarith.asm    show some simple C code and corresponding nasm code
+;                 the nasm code is one sample, not unique
+;
+; compile:	nasm -f elf -l intarith.lst  intarith.asm
+; link:		gcc -o intarith  intarith.o
+; run:		intarith
+;
+; the output from running intarith.asm and intarith.c is:	
+; c=5  , a=3, b=4, c=5
+; c=a+b, a=3, b=4, c=7
+; c=a-b, a=3, b=4, c=-1
+; c=a*b, a=3, b=4, c=12
+; c=c/a, a=3, b=4, c=4
+;
+;The file  intarith.c  is:
+;  /* intarith.c */
+;  #include <stdio.h>
+;  int main()
+;  { 
+;    int a=3, b=4, c;
+;
+;    c=5;
+;    printf("%s, a=%d, b=%d, c=%d\n","c=5  ", a, b, c);
+;    c=a+b;
+;    printf("%s, a=%d, b=%d, c=%d\n","c=a+b", a, b, c);
+;    c=a-b;
+;    printf("%s, a=%d, b=%d, c=%d\n","c=a-b", a, b, c);
+;    c=a*b;
+;    printf("%s, a=%d, b=%d, c=%d\n","c=a*b", a, b, c);
+;    c=c/a;
+;    printf("%s, a=%d, b=%d, c=%d\n","c=c/a", a, b, c);
+;    return 0;
+; }
+
+        extern printf		; the C function to be called
+
+%macro	pabc 1			; a "simple" print macro
+	section .data
+.str	db	%1,0		; %1 is first actual in macro call
+	section .text
+				; push onto stack backwards 
+	push	dword [c]	; int c
+	push	dword [b]	; int b 
+	push	dword [a]	; int a
+	push	dword .str 	; users string
+        push    dword fmt       ; address of format string
+        call    printf          ; Call C function
+        add     esp,20          ; pop stack 5*4 bytes
+%endmacro
+	
+	section .data  		; preset constants, writeable
+a:	dd	3		; 32-bit variable a initialized to 3
+b:	dd	4		; 32-bit variable b initializes to 4
+fmt:    db "%s, a=%d, b=%d, c=%d",10,0	; format string for printf
+	
+	section .bss 		; unitialized space
+c:	resd	1		; reserve a 32-bit word
+
+	section .text		; instructions, code segment
+	global	 main		; for gcc standard linking
+main:				; label
+	
+lit5:				; c=5;
+	mov	eax,5	 	; 5 is a literal constant
+	mov	[c],eax		; store into c
+	pabc	"c=5  "		; invoke the print macro
+	
+addb:				; c=a+b;
+	mov	eax,[a]	 	; load a
+	add	eax,[b]		; add b
+	mov	[c],eax		; store into c
+	pabc	"c=a+b"		; invoke the print macro
+	
+subb:				; c=a-b;
+	mov	eax,[a]	 	; load a
+	sub	eax,[b]		; subtract b
+	mov	[c],eax		; store into c
+	pabc	"c=a-b"		; invoke the print macro
+	
+mulb:				; c=a*b;
+	mov	eax,[a]	 	; load a (must be eax for multiply)
+	imul	dword [b]	; signed integer multiply by b
+	mov	[c],eax		; store bottom half of product into c
+	pabc	"c=a*b"		; invoke the print macro
+	
+diva:				; c=c/a;
+	mov	eax,[c]	 	; load c
+	mov	edx,0		; load upper half of dividend with zero
+	idiv	dword [a]	; divide double register edx eax by a
+	mov	[c],eax		; store quotient into c
+	pabc	"c=c/a"		; invoke the print macro
+
+        mov     eax,0           ; exit code, 0=normal
+	ret			; main return to operating system
+