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Lebell · 02-26-2005, 11:59 AM

Just for giggles and grins, here's the same thing in assembler.

----------------------------------------------------------------

Quote:

;*****************************************************************************************
STACK SEGMENT PARA STACK 'Stack'
DW 32 DUP(0)
STACK ENDS
;*****************************************************************************************
DATASEG SEGMENT PARA 'Data'

NUMA DB 40 ;first number in range to check
NUMB DB 65 ;last number in range to check
CNT1 DB 0 ;loop counter 1
CNT2 DB 0 ;loop counter 2
PCNT DB 0 ;'prime' counter for prime numbers found
PFLAG DB ? ;'prime' flag to signal that a prime number has been found
PTBL DB 14 DUP (0) ; table to store prime numbers
DISPA DB 'Number A = ','$'
DISPB DB 'Number B = ','$'
DISPNO DB 'Number of Primes found: ','$'
DISPPRIME DB 'The Prime numbers between them are: ','$'

NEGSIGN DB '

ASCVAL DB 5 DUP (' '), '$'

DATASEG ENDS
;*****************************************************************************************
CODESEG SEGMENT PARA 'Code'
MAIN PROC FAR
ASSUME SS:STACK,DS

ATASEG,CS:CODESEG ;assign the stack,data and code pointers
MOV AX,DATASEG ;Set the address of the
MOV DS,AX ; segment into DS (boiler plate)

MOV BH,NUMA ;initialize BH as the outer loop counter which will be ;the number to be tested for prime
;begin outer loop
L10: ;begin outer loop, from NUMA to NUMB
MOV PFLAG, 1 ;initialize the 'prime' flag to true

CMP BH,NUMB ;test for exit outer loop, is the counter > number B?
JG L40 ;if it is, then exit from outer loop and testing

;begin inner loop
MOV BL,2 ;begin inner loop, from 2 to 1/2 of number being tested
L20:
MOV AX,BH
IDIV BL ;divide the number, in BH, by the current counter value
CMP AH,00 ;test for a remainder
JNE L25 ;if there is a remainder, jump to the end of loop test
;and do NOT set the 'prime' flag to false
MOV PFLAG, 0 ;otherwise, set the 'prime' flag to false and
JMP L30 ;exit the inner loop

L25:
MOV AH,BH
SHR AH,1 ;shift right effectively divides AH by 2, dropping any remainder
CMP BL, AH ;test end of inner loop, is the loop counter, BL, > 1/2 the value of
; the number being tested (the outer loop counter)?
JG L30 ;if so, then exitout of inner loop
INC BL ;increment the inner loop counter by 1
JMP L20 ;end inner loop, jump back to beginning at L20
;end inner loop
;test for prime flag
L30:
CMP PFLAG,1 ;check the 'prime' flag. If it's still true, then store the number
JNE L35 ;jump to L35 if not true
MOV PTBL + PCNT, BH ;else, store the number in PTBL
INC PCNT ;and increment the 'prime' counter

L35:
INC BH ;increment the outer loop counter by 1
JMP L10 ;end outer loop, jump back to beginning at L10
;end outer loop

;end of testing logic
;begin printing results code

L40:

MOV AH,09H ;request for display
LEA DX, DISPA ; for display A label
INT 21H

CALL CONVERT
MOV AH,09H
LEA DX,ASCVAL

MOV AX,4C00H ; end
INT 21H ; processing

MAIN ENDP
;--------------------------------------------------------------------------------------------------
; This procedure converts a hex based number into an ASCII value
; for display purposes

CONVERT PROC NEAR
MOV CX,10
MOV AX,HVAL
LEA SI,ASCVAL ; load the first position into SI

B20: ; added - this part can do a negative
CMP AX, 0 ; test if neg
JGE B25 ; if >=0, then jump to normal processing
NEG AX ; twos comp the AX register if it is zero to get the pos equ

MOV [SI],'-' ; put a negative sign there

B25: ADD SI, 4

CMP AX, CX
JB B30

XOR DX, DX
DIV CX

OR DL,30H
MOV [SI],DL

DEC SI
JMP B20

B30:
OR AL,30H
MOV [SI],AL

RET

CONVERT ENDP
;---------------------------------------------------------------------------------------------------
; This procedure displays one character to the screen.

DISPLAY PROC NEAR
PUSHA ; preserve registers
LEA DX, ASCVAL
MOV AH,09H
INT 21H
POPA
RET
DISPLAY ENDP

;---------------------------------------------------------------------------------------------------
CODESEG ENDS
END MAIN