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Old Jun 30th, 2012, 7:09 AM   #1
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Error Handling For Null Input[Question]

Well this is not so much of a need, but i really want to learn how to do error handling **embly language[TASM]
Basically if the user just types or presses enter the code will go back to the same question with probably a message box or writing stating that they must put at least one letter.

Enter string: (user just presses enter)
(message box or ill just print error message)[cuz im not sure if there is message box in ASM or not haha]
Enter string: A [this is still considered string so its accepted]
you entered: A

         TITLE error handling
         .model SMALL
         .stack 100h

PINPUT   db "Enter String: $"
SINPUT   db 14 dup("$")
CRLF     db 13,10,"$"
PENTER   db "You Entered: $"
UERROR   db "Error must enter something! $"

BEGIN:    mov ax, @data
          mov ds, ax
          mov es, ax

          mov al, 03h    		 ; clear screen
          mov ah, 00h
          int 10h

names:	  mov dx, OFFSET PINPUT		; Print Enter String: 
          mov ah, 09h	 ; DOS screen output function call
          int 21h		; universal DOS function call
          mov byte ptr SINPUT, 11
          mov dx, OFFSET SINPUT			; scan Input	
          mov ah, 0Ah 					
		  int 21h

		  cmp SINPUT, 21h  ;because 21h starts characters
		  jl Erroring  ; jump if something below 21h is entered
		  jmp Prnt	 ; skip error and print user entered value
		  mov dx, OFFSET UERROR 	  ; print error message
          mov ah, 09h
          int 21h
		  mov dx, OFFSET CRLF 		; print \n
          mov ah, 09h
          int 21h
		  jmp names
		  mov dx, OFFSET CRLF 		; print \n
          mov ah, 09h
          int 21h
		  mov dx, OFFSET PENTER		; print You entered:
          mov ah, 09h
          int 21h		 		  
		  mov SI, 0002
          lea DX, SINPUT[SI]  	; Print string entered
          mov ah, 09h
		  int 21h
          mov ah, 4ch
          int 21h
          end BEGIN
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Old Jul 2nd, 2012, 1:09 AM   #2
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Re: Error Handling For Null Input[Question]

the control flow of your program looks correct, so at a glance I dont see an issue. What is it doing that you dont expect?
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Old Jul 10th, 2012, 4:37 PM   #3
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Re: Error Handling For Null Input[Question]

if you want to test for an empty string, question is the string null terminated? if so, test for null (0) at the base index of the character array for the string.
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