;----------------------------------------------------------------------- ; PRIME3.ASM ; ; Program that tests values between 0 and some upper limit displaying ; each prime number and total primes detected. ; ; ;----------------------------------------------------------------------- org 100h ;Code starts at offset 0100h. use16 ;Use 16-bit code. jmp Start ;Go to start of program. ;======================================================================= ; Program Data & Constants. ;======================================================================= ; C O N S T A N T S ;----------------------------------------------------------------------- ; ;DOS Kernel Int 21h function codes. ; CharIn = 01h ;Read character from STDIN to AL (with echo). CharOut = 02h ;Write character to STDOUT from DL. AuxIn = 03h ;Read character from STDAUX to AL.* AuxOut = 04h ;Write character to STDAUX from DL. LPOut = 05h ;Write character to printer from DL.* DirConOut = 06h ;Write character directly to STDOUT from DL.* DirConIn = 06h ;Read character directly from STDIN to AL.* DCINoEcho = 07h ;Read character (no echo) from STDIN to AL.* WaitByte = 08h ;Console input (no echo) AL holds character. StrOut = 09h ;Output '$' terminated string addressed by DS:DX. SINStatus = 0Bh ;Return STDIN status to AL. FlshSTDIN = 0Ch ;Flush STDIN and read character as per AL.* ; ;ASCII codes to 1Fh. ; Null = 00h ;Null character. SOH = 01h ;Start of heading. STX = 02h ;Start of text. ETX = 03h ;End of text. EOT = 04h ;End of transmission. ENQ = 05h ;Enquiry. ACK = 06h ;Acknowledge. Bell = 07h ;Bell sound. BckSpc = 08h ;Backspace. Tab = 09h ;Horizontal tab. LinF = 0Ah ;Line feed. VTab = 0Bh ;Vertical tab. FFeed = 0Ch ;Form Feed. CRet = 0Dh ;Carriage Return. ShOut = 0Eh ;Shift Out. ShIn = 0Fh ;Shift In. StrTrm = 24h ;String terminator. ;----------------------------------------------------------------------- ; ;Program Constants ; ;For NumOut16 and Asc2Bin16. ; NSLen = 06 ;Length of numeric strings. Dvsr = 10 ;Divisor for ASCII-Binary conversion. ; ;For IsPrime. ; MinDvsr = 03 ;Minimum divisor for trial division. RootLim = 255 ;Maximum allowed root for trial division. MaxVal = 700 ;Limit of prime testing. ; ;----------------------------------------------------------------------- ; D A T A ;----------------------------------------------------------------------- ; ;Data for NumOut16. ; NumStr db NSLen dup 0 ;Space for string after conversion. TstVal dw 0 ;Value to be converted to string. Top dw 0 ;Pointer to current end-of-string. ; ;Data for Asc2Bin16. ; GI16Str db NSLen dup 0 ;Space for String before conversion. BinVal dw 0 ;Holds converted binary value. ; ;Data for IsPrime. ; NumIn dw 0 ;Space to save number to be tested. ; ;Data for RunPgm. ; NxtVal dw 0 ;Value to be tested. TotPrm dw 0 ;Total Primes Detected. ; ;----------------------------------------------------------------------- ; ; General Texts. ; ;Program name string (includes newlines). ; PgmTxt db 'Prime Number Finder' db CRet, LinF db '----- ------ ------' db CRet, LinF db StrTrm Txt01 db 'List of primes between 0 and ' db StrTrm TotTxt db 'Total Primes = ' db StrTrm CTxt db ', ' db StrTrm ; ;Prime message; ; StrtMsg db 'Press any key to start...' db StrTrm ClrMsg db CRet db ' ' db StrTrm FinMsg db '*** RUN COMPLETE ***' db StrTrm ; ;Continuation message. ; ConMsg db 'Run Again? (Y/N): ' db StrTrm ; ;Quit Message. ; QMsg db 'Press any key...' db StrTrm ;----------------------------------------------------------------------- ; E N D O F D A T A ;----------------------------------------------------------------------- ;----------------------------------------------------------------------- ; S U B R O U T I N E S ;----------------------------------------------------------------------- ; ;RingBell - Sound the bell!!!!! ; RingBell: pusha ;Save all regs. mov ah, CharOut ;Function code to AH. mov dl, Bell ;Bell code to DL. int 21h ;DING DONG popa ;Restore regs. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ;NewLine:- Display line feed on STDOUT. ; NewLine: pusha ;Preserve all regs. mov dl, LinF ;Get ASCII code to DL. mov ah, CharOut ;Function code to AH. int 21h ;Output character. mov dl, CRet ;Get ASCII code to DL. mov ah, CharOut ;Function code to AH. int 21h ;Output character. popa ;Restore all regs. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ;GetYN - Ask if user wishes to Run Again (Y/N)? ; ; Returns: CX = 0 -> No ; CX = 1 -> Yes. ; GetYN: mov cx, 0 ;Set return flag to No. mov dx, ConMsg ;Addr. of continue message to DX. mov ah, StrOut ;Display message. int 21h GY01: mov ah, WaitByte ;Code to get char. from STDIN. int 21h ;Get character to AL. cmp al, 'Y' ;Is it 'Y'? je SetY ;Yes. Set flag to yes. cmp al, 'y' ;Is it 'y'? je SetY ;Yes. Set flag to yes. cmp al, 'N' ;Is it 'N'? je GYXit ;Yes. Just quit. cmp al, 'n' ;Is it 'n'? je GYXit ;Yes. Just quit. ; ;Here when character invalid. ; call RingBell ;Ring the bell! jmp GY01 ;And try again. SetY: mov cx, 1 ;Set return flag to Yes. GYXit: ; ; Echo character entered, get carriage return, and quit ; with CX = 1 - YES; or CX = 0 - NO. ; mov dl, al ;Copy response to DL. mov ah, CharOut ;Code to AH. int 21h ;Display character. GYX01: ; ; Allow ONLY carriage return. ; mov ah, WaitByte ;Code to Ah. int 21h ;Wait for next byte. cmp al, CRet ;Is it carriage return? je GYX02 ;Yes. Go to exit. call RingBell ;No. Ring the bell. jmp GYX01 ;And try again. GYX02: call NewLine ;Move to new line. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ;QWait - Display quit message and await keystroke. ; QWait: mov ah, CharOut ;Output line feed. mov dl, LinF int 21h mov ah, CharOut ;Output . mov dl, CRet int 21h mov dx, QMsg ;Address of text to DX. mov ah, StrOut ;Code to AH. int 21h ;Display message. KWait: mov ah, WaitByte ;Code to AH. int 21h ;Await keystroke. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ;ShftStr - Shift characters in string one byte right. ; - On Entry - AL holds byte to be added to head of string. ; Target string should have... ; (i) '$' in byte [0] of string. ; (ii)'Top' = Base address of string. ; ; Registers preserved on exit. ; ShftStr: pusha ;Save all registers. AL = new character. mov bx, [Top] ;Get pointer to current end-of-string. mov cx, bx ;Save in CX. mov al, [bx] ;Get byte at end of string. inc bx ;Advance to next byte. mov [bx], al ;And shuffle byte one place right. mov [Top], bx ;Save new 'Top' pointer. SSLoop: cmp cx, NumStr ;Have we shuffled all characters? je SSExit ;Yes. Go to exit. dec cx ;No. Decrement source pointer. mov bx, cx ;Copy to BX. mov al, [bx] ;Get next byte to be moved. inc bx ;Advance pointer to destination address. mov [bx], al ;Place byte in destination address. jmp SSLoop ;And check for end. SSExit: popa ;Restore all registers. mov [NumStr], al ;Add new byte to first byte of string. ret ;Return to caller ; ;----------------------------------------------------------------------- ; ;NumOut16 - Display word in AX as decimal string. ; ;Associated data items are: ; ; TstVal = Value to be displayed. ; NumStr = Decimal string equivalent. ; Top = Pointer to current end-of-string. ; NumOut16: mov cx, NumStr ;String addr. to CX. mov [Top], cx ;Save as buffer limit. mov cl, StrTrm ;String terminator to CL. mov [NumStr], cl ;Place in first byte of string. NxtDig: xor dx, dx ;Clear DX. mov bx, Dvsr ;Divisor to BX div bx ;Divide number by ten.AX = Quo., DX = Mod. or dl, 30h ;Convert modulus to ASCII. xchg cx, ax ;Save quotient to CX. mov al, dl ;Transfer byte to AL. call ShftStr ;Shuffle chars and add new one to string. xchg ax, cx ;Restore quotient. cmp ax, 0 ;Are we at the end? je N8Xit ;Yes. Quit. jmp NxtDig ;No. Do next digit. N8Xit: mov ah, StrOut ;All bytes done... mov dx, NumStr ;...so display string. int 21h ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ; IsPrime - Determine whether 16-bit value in AX is prime or composite. ; Uses trial division. Maximum divisor is limited to 255. If ; required divisor exceeds this value, IsPrime returns CX = 2. ; ; On Entry: AX = Value to be tested. ; ; On Exit : CX = 0 when composite. ; CX = 1 when prime. ; CX = 2 when limit of division exceeded. ; IsPrime: mov [NumIn], ax ;Save number to NumIn. ; ; Check whether number is 0, 1, or 2. ; cmp ax, 2 ;Is it 2? ja TstOdd ;No. Greater, see if odd. je Prime ;Yes. Flag as prime and quit. jmp Composite ;No. Less, must be 0 or 1. TstOdd: cmp ax, MinDvsr ;Is it 3? jz Prime ;Yes. Flag as prime. mov dx, ax ;Copy number to DX. and dx, 1 ;No. Mask to bit 0. jnz OddVal ;If NOT clear must be odd. mov bx, 2 ;else even so set divisor to 2. shr ax, 1 ;Halve the value being tested. jmp Composite ;and got to composite exit. OddVal: ; ; Find limit for trial division as root AX. ; mov bx, MinDvsr ;Get lowest divisor to BX. NxtNum: mov ax, bx ;Copy divisor to AX. mul bx ;Calculate AX squared to DX:AX cmp ax, [NumIn] ;Is result >= value to be tested? jae GotLim ;Yes. Perform trial division. inc bx ;No. Increment to next number. cmp bx, RootLim ;Is root beyond limit? ja NoLimit ;Yes. Flag unable to process. jmp NxtNum ;No. Try again. GotLim: mov cx, bx ;Save limit of trial to CX. mov bx, MinDvsr ;Try lowest divisor first. NxtDiv: mov ax, [NumIn] ;Restore number to be tested to AX. xor dx, dx ;Clear DX for division. div bx ;Calculate AX DIV BX. Modulus to DX. cmp dx, 0 ;Is modulus = zero? je Composite ;Yes. Flag as composite. inc bx ;No. Move to next divisor. cmp bx, cx ;Have we reached limit of trial? ja Prime ;Yes. Value is prime. jmp NxtDiv ;And perform next division. NoLimit: mov cx, 2 ;Set "Unable to process" flag. jmp Return ;And quit. Composite: mov cx, 0 ;Clear return flag. jmp Return ;And go to exit. Prime: mov cx, 1 ;Set return flag. Return: ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ; Comma - display comma between values.. ; Comma: mov dx, CTxt ;Address of text to DX. mov ah, StrOut ;Code to AH. int 21h ;Display it. ret ;Return to caller. ; ;---------------------------------------------------------------------- ; ; InitPgm - Initialise program by displaying program name, clears ; value to be tested and total primes detected. ; InitPgm: mov dx, PgmTxt ;Address of heading to DX. mov ah, StrOut ;Code to display string. int 21h ;Display it. mov dx, Txt01 ;Address of text to DX. mov ah, StrOut ;Code to AH, int 21h ;Output start message. mov ax, MaxVal ;Get limit of test. call NumOut16 ;...and output. call NewLine ;Move to new line. mov ax, 0 ;Clear accumulator... mov [NxtVal], ax ;...Value to be tested... mov [TotPrm], ax ;...and total primes. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ; RunPgm - ; RunPgm: mov ax, [NxtVal] ;Restore next value to AX. call IsPrime ;Perform prime test. cmp cx, 0 ;Is result composite? je TstEnd ;Yes. Look for end of test. cmp cx, 2 ;No. Is result out of range? je TstEnd ;Yes. Test for end. ; ; Here when result is prime. ; mov ax, [NxtVal] ;Get next value. call NumOut16 ;Display it. call Comma ;and a comma. inc [TotPrm] ;Increment total primes. TstEnd: inc [NxtVal] ;Increment value to be tested. mov ax, [NxtVal] ;Get it to AX. cmp ax, MaxVal ;Is it end? ja RPXit ;Yes. jmp RunPgm ;No. RPXit: call NewLine ;Finished. Move to new line for total. ret ;Return to caller. ; ;----------------------------------------------------------------------- ; ; ClosePgm - ; ClosePgm: mov dx, TotTxt ;Address of text to DX. mov ah, StrOut ;Code to AH. int 21h ;Display it. mov ax, [TotPrm] ;Get total to AX. call NumOut16 ;Display it. call NewLine ;Move to next line. mov dx, FinMsg ;Display "*** RUN COMPLETE ***. mov ah, StrOut int 21h ret ;Return to caller. ; ;----------------------------------------------------------------------- ; E N D O F S U B R O U T I N E S ;----------------------------------------------------------------------- ;======================================================================= ; M A I N P R O G R A M ;======================================================================= ; ; ; Program that tests values between 0 and some upper limit displaying ; rolling fields for value being tested and total primes detected. ; Start: call InitPgm ;Initialise program. call RunPgm ;Run it... call ClosePgm ;...and closedown. ; ;See if user wants to run again. ; call NewLine ;Move to new line. call GetYN ;Run Again (Y/N)?. cmp cx, 1 ;Is reply 'y'? je Start ;Yes. Loop. call QWait ;Display quit message. int 20h ;Terminate Program! ; ;======================================================================= ; E N D O F C O D E ;======================================================================= ;