time1.asm

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;==========================================
;A little assembly app that shows the current date and time.
;It can be done a lot easier, but this way you will 
;see how to do some basic memory manipulation, and how to use 'variables'.
;==========================================

.model small
 .stack

;===========================
;Data segment starts here
;===========================
 .data
date_str db "Current date is: yyyy-mm-dd", 0Ah, 0Dh, "$"
time_str db "Current time is: hh.mm.ss:xx", 0Ah, 0Dh, "$"
min_size dw ?
padd_chr db  ?


;===========================
;Code segment starts here
;===========================
 .code
main proc
 mov ax, seg @data  ;First we get the data segment address
 mov ds, ax   ;and store it into ds

 mov [min_size], 02h  ;Results should always be at least two digits
 mov [padd_chr], '0'  ;Use '0' as padding-character

 mov ah, 2Ah   ;Then we call int 21h,2Ah, which will give
 int 21h   ;us the current date

 lea di, date_str  ;Then we load the address of the date_str string
 add di, 17   ;and set si to point at the first y in yyyy-...


 mov ax, cx   ;Next we mov cx to ax and
 call todec   ;call todec
 inc di   ;We skip the '-' character...

 xor ax, ax   ;Then we empty ax
 mov al, dh   ;And set the low-byte of ax to dh
 call todec
 inc di   ;Skip character in string...

 xor ax, ax   ;Empty ax
 mov al, dl   ;Set low-byte to dl
 call todec   ;Convert it to base10


 lea di, time_str  ;Now we load the time_str string
 add di, 17   ;And set the correct pointer offset

 mov ah, 2Ch   ;And then we call int 21h,2Ch
 int 21h   ;which will give us the current time


 xor ax, ax   ;Empty ax
 mov al, ch   ;Set low-byte to ch
 call todec   ;Convert it to base10
 inc di   ;Skip character

 mov al, cl   ;Set low-byte to cl
 call todec   ;Convert to base10
 inc di   ;Skip character

 mov al, dh   ;Set low-byte to dh
 call todec   ;Convert to base10
 inc di   ;Skip character

 mov al, dl   ;Set low-byte to dl
 call todec   ;Convert to base10


 mov dx, offset date_str ;Now load offset of the date_str string into dx
 call print   ;And print the (modified) string

 mov dx, offset time_str ;Load offset of the time_str string into dx
 call print   ;And print the (modified) string

 mov ax, 4C00h  ;Do a clean exit(error code=00)
 int 21h

 

;===================================================================
;todec - converts the contents of ax into base10 ascii character(s)
;        of length bx
;        min_size defines minimum length of result, and padd_char
;        defines the padding character.
;The result(s) are stored at ds:di
;===================================================================
todec proc
 push ax   ;Save all registers
 push bx
 push cx
 push dx


 xor cx,cx   ;Empty the POP counter
 mov bx,10   ;Base divisor
decloop:  
 xor dx,dx   ;Set the high 16-bits to 0
 div bx   ;Preform division(dx=remainder, ax=quotient)
 inc cx   ;Increase the counter
 push dx   ;and save the remainder
 cmp ax,0   ;If the quotient != 0 
 jnz decloop   ;then get one more number


 mov bx, [min_size]  ;Load min_size value into bx
 mov dl, [padd_chr]  ;Load padd_chr value into dl
padd_result:
 cmp cx, bx   ;Is cx >= min_size?
 jge poploop   ;If so, proceed

 mov byte ptr ds:[di], dl ;Else padd with padd_chr
 inc di   ;and increase string pointer
 dec bx   ;decrease bx
 jmp padd_result  ;and test for more padding
 

poploop:
 pop dx   ;Get the number of the stack
 add dl,'0'   ;and add '0' to it
 mov byte ptr ds:[di], dl ;Modify the string at ds:di
 inc di   ;Increase the string pointer
 dec cx   ;Decrease the loop counter
 jnz poploop 


 pop dx   ;Restore all registers
 pop cx
 pop bx
 pop ax
 ret    ;And return from call
todec endp


;===========================================================
;print - prints the string pointed to by dx using int 21h,09
;===========================================================
print proc
 push ax   ;Save ax
 push ds   ;and ds onto the stack

 mov ax, @data  ;Then get the address of the data segment
 mov ds, ax   ;and store it into ds
 mov ax, 0900h  
 int 21h   ;and then print the message pointed to by dx
 
 pop ds   ;Retrieve ds
 pop ax   ;and ax from stack

 ret
print endp

main endp
end main