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