Section 7
CODE EXAMPLE: GET TIME OF DAY

INTRODUCTION

The first example is of a program that uses the system time of day. This example uses a conditional assembly to decide between two ways to get the time of day. One way is to use the DOS time of day function; the other way, illustrated by the second code example, uses the BIOS time of day function. The second example can be used to replace the standard DOS call to get the time of day. This second example will return the time of day much faster than the standard DOS call.

FIRST EXAMPLE

This example runs until a set time of day occurs and then terminates. This code gets the time of day information from the DOS command line input data. If there is bad input data, then an error message is displayed, informing the user what the correct input data format is. While the program is waiting for the terminate time, it will scan the keyboard for an escape key to terminate the program on user demand.

; Wait for Time
;This program can be executed inside of a .BAT file to
;  stall execution of the .BAT file until a set time of day
;?????????????????????????????????????????????????????????? ???
;conditional assembly flag, 0 to use DOS, 1 to use BIOS example
.MODEL tiny
use_bios_flag EQU 1
;----------- stack area ---------------
.STACK 500
;--------------------------------------
.CODE
;*************  @@@@@@@@@@@@@@  ***************
start   proc    near
        mov     bx,80H        ;index command line data
        mov     al,[bx]       ;get size of string variable
        mov     ax,cs
        mov     ds,ax         ;reset data segment
        mov     psp_seg,es    ;save PSP address
        mov     es,ax         ;reset extra segment
        cmp     al,4          ;is there data in string
        jb      exit_bad      ;branch if no data
        inc     bx
        inc     bx            ;point to start of data
      ;get number out of buffer area
        call    get_number
        jc      exit_bad      ;branch if number bad
        mov     wait_hour,al  ;save number in hour
        cmp     al,23         ;?? number too large ??
        ja      exit_bad      ;branch is too large
      ;check the number terminating character
        cmp     ah,":"
        jne     exit_bad      ;branch if not :
      ;point to start of next number
        inc     bx
      ;get next number out of buffer area
        call    get_number
        jc      exit_bad      ;branch if number bad
        cmp     al,59         ;?? number too large ??
        ja      exit_bad      ;branch if too large
        mov     wait_minute,al     ;save number to minute
   ;display executing wait message
        mov     ah,9        ;set DOS function number
        lea     dx,wait_message
        int     21H         ;DOS call to display message
;________________________________
;**********  !!!!!!!!  **********
wait_loop:
      ;scan keyboard for keys
        mov     ah,1
        int     16H
        jz      wait_no_key     ;branch if no key
        mov     ah,0            ;if here then keyboard data
        int     16H             ;get key code from buffer
        cmp     ax,3B00H        ;check key code
        je      exit            ;branch if exit key
        cmp     al,1BH          ;check for ESC key
        je      exit            ;branch if ESC key
wait_no_key:
   ;find out what time it is
;conditional assembly ????????????????????
      ;use this code if linking to code in this section
IF use_bios_flag
        call    get_time_of_day
      ;else use this code if calling DOS for time
ELSE
        mov     ah,2CH
        int     21H             ;get current time of day
ENDIF
        cmp     ch,wait_hour
        jne     wait_loop       ;loop if not time
        cmp     cl,wait_minute
        jne     wait_loop       ;loop if not time
;^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
exit:
        mov     ah,4CH
        int     21h             ;terminate program
;!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
exit_bad:
        mov     ah,9
        lea     dx,exit_bad_message
        int     21H             ;DOS call to display message
        jmp     exit
;  ***** ^^^^^^^^ ***** ^^^^^^^^ ****
get_number:
 ;on entry BX indexes ASCII number data in PSP segment area
 ;on exit if carry clear,
  ; register AL has binary number, from 0 to 99
  ; BX indexes past the number,
  ; AH has exiting character code indexed by BX
     push ds
     mov  ds,psp_seg
     mov  al,[bx]
     inc  bx
     call number_check
     jc   get_number_bad
     mov  ah,al
     mov  al,[bx]
     call number_check
     jc   get_number_1
get_number_2a:
     cmp  ah,0
     je   get_number_2
     add  al,10
     dec  ah
     jmp  get_number_2a
get_number_2:
     inc  bx
     mov  ah,al
     mov  al,[bx]
get_number_1:
     cmp  al,":"
     je   get_number_1a
     cmp  al,0DH
     jne  get_number_bad
get_number_1a:
     xchg al,ah
     pop  ds
     clc       ;set good number flag
     ret
get_number_bad:
     pop  ds
     stc       ;set bad number flag
     ret
;#################################################
number_check:
   ;this code checks for ASCII number in AL
    ; if it finds a number, then it makes it binary
    ; and returns with carry clear, else carry set
     cmp  al,"0"
     jb   number_bad
     cmp  al,"9"
     ja   number_bad
     and  al,0FH
     clc
     ret     stc
     ret
;*************************
start     endp
;+++ this routine combines data and code into one segment +++
; define data area
psp_seg         dw      0
wait_hour       db      0
wait_minute     db      0

wait_message    db     0DH,0AH,0DH,0AH
        db   "Wait in progress, Press [ESC] to exit",0DH,0AH
                db      "$"
exit_bad_message        db      0DH,0AH
        db   "To use TimeWait program enter timeout data "
        db   "from command line as example:",0DH,0AH,0DH,0AH
        db     "TimeWait 11:30",0DH,0AH,0DH,0AH
        db     "Note, timeout hours vary from 0 to 23, "
        db     "and minutes from 0 to 59.",0DH,0AH
        db     "$"
;______________________________________
     end  start