Эмулятор процессора Intel 8086 версия 4.05 (ENG) / asm_files / convert_string_number_to_binary.asm

Assembler Source Code a:link {text-decoration: none} a:visited {text-decoration: none} a:hover {text-decoration: none; color:#ff0000}     ; convert_string_number_to_binary.asm name "str2bin" ; convert string number to binary! ; this program written in 8086 assembly language to ; convert string value to binary form. ; this example is copied with major modifications ; from macro "scan_num" taken from c:\emu8086\inc\emu8086.inc ; ; the original "scan_num" not only converts the string number ; but also reads the string from the keyboard and supports ; backspace key, this example is a shorten version ; of original "scan_num" macro. ; here we assume that the string number is already given, ; and the string number does not contain non-digit chars ; and it cannot cause buffer overflow (number is in word range ; and/or has only 4 digits). ; negative values are allowed in this example. ; the original "scan_num" does not allow to enter non-digits ; and it also checks for buffer overflow. ; you can the original file with other macro definitions ; in c:\emu8086\inc\emu8086.inc org 100h jmp start ; text data: msg1 db 0Dh,0Ah, " enter any number from -32768 to 65535 inclusive, or zero to stop: $" msg2 db 0Dh,0Ah, " binary form: $" ; buffer for int 21h/0ah ; fist byte is buffer size, ; second byte is number of chars actually read (set by int 21h/0ah). buffer db 7,?, 5 dup (0), 0, 0 ; for result: binary dw ? start: ; print welcome message: mov dx, offset msg1 mov ah, 9 int 21h ; input string: mov dx, offset buffer mov ah, 0ah int 21h ; make sure the string is zero terminated: mov bx, 0 mov bl, buffer[1] mov buffer[bx+2], 0 lea si, buffer + 2 ; buffer starts from third byte. call tobin ; the number is in cx register. ; for '-1234' it's 0fb2eh mov binary, cx jcxz stop ; print pre-result message: mov dx, offset msg2 mov ah, 9 int 21h ; print result in binary: mov bx, binary mov cx, 16 print: mov ah, 2 ; print function. mov dl, '0' test bx, 1000000000000000b ; test first bit. jz zero mov dl, '1' zero: int 21h shl bx, 1 loop print ; print binary suffix: mov dl, 'b' int 21h jmp start ; loop stop: ret ; return control to the operating system. ; this procedure converts string number to ; binary number. number can have a sign ('-'). ; the result is stored in cx register. ; parameters: ; si - address of string number (zero terminated). tobin proc near push dx push ax push si jmp process ;==== local variables ==== make_minus db ? ; used as a flag. ten dw 10 ; used as multiplier. ;========================= process: ; reset the accumulator: mov cx, 0 ; reset flag: mov cs:make_minus, 0 next_digit: ; read char to al and ; point to next byte: mov al, [si] inc si ; check for end of string: cmp al, 0 ; end of string? jne not_end jmp stop_input not_end: ; check for minus: cmp al, '-' jne ok_digit mov cs:make_minus, 1 ; set flag! jmp next_digit ok_digit: ; multiply cx by 10 (first time the result is zero) push ax mov ax, cx mul cs:ten ; dx:ax = ax*10 mov cx, ax pop ax ; it is assumed that dx is zero - overflow not checked! ; convert from ascii code: sub al, 30h ; add al to cx: mov ah, 0 mov dx, cx ; backup, in case the result will be too big. add cx, ax ; add - overflow not checked! jmp next_digit stop_input: ; check flag, if string number had '-' ; make sure the result is negative: cmp cs:make_minus, 0 je not_minus neg cx not_minus: pop si pop ax pop dx ret tobin endp

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