;***********************************************************************************************************
;*                       AUTHOR: ANUEBUNWA VICTOR OGECHUKWU                                                *
;*                                                                                                         *
;*               SUBROUTINE TO CONVERT CHARACTERS IN MEMORY TO A DECIMAL VALUE                             *
;* Subroutine CHAR2INTR converts characters in memory to a decimal value and stores it in AX.              *
;* i.e '1','2','3','4' in memory ==> 1234 in AX                                                            *
;* ............................................HOW TO USE................................................. *
;* (1) Load the starting address of the memory into SI register.                                           *
;* (2) Call CHAR2INTR.                                                                                     *
;***********************************************************************************************************

;         SAMPLE PROGRAM
.MODEL SMALL
.STACK
.DATA
	AVON DB ?
.CODE
START:		MOV AX, @DATA
			MOV DS, AX
			
			MOV AH, 3FH
			LEA DX, AVON
			INT 21H					;Reads characters into memory, using AVON as a starting address
			
			LEA SI, AVON			;Loads starting address into SI
			CALL CHAR2INTR			;Calls CHAR2INTR to convert characters to a decimal value
			MOV DX, AX				;Puts decimal value into DX
			MOV AH, 02H
			INT 21H					;Displays character whose ASCII code equals the decimal value
			
			MOV AH, 4CH
			INT 21H

;Subroutine CHAR2INTR
CHAR2INTR PROC
			PUSH BX
			PUSH CX
			PUSH DX
			PUSH SI
			PUSHF
			
			MOV AX, 0000H
			MOV CX, 0000H
CLOOP1:		MOV AX, [SI]			;Loads character currently pointed to into AX
			CMP AL, '9'
			JNLE XCLOOP1			;Exits loop if character is not less or equal to '9'
			CMP AL, '0'
			JNGE XCLOOP1			;Exits loop if character is not greater or equal to '0'
			INC CL				;Else, Keeps count of the number of characters being processed
			INC SI				;Moves pointer to the next character
			SUB AL, 30H			;Converts character to digit
			PUSH AX				;Pushes digit to stack
			JMP CLOOP1			;continues loop

XCLOOP1:	MOV BX, 0001H
			MOV DX, 0000H
CLOOP2:		CMP CL, 0				;Checks number of characters processed
			JE XCLOOP2			;Exits loop if no character was processed i.e CL = 0
			POP AX				;Else, pops digit from stack to AX
			MUL BL				;Multiplies digit with it's PLACEMENT-VALUE. RECALL: unit = 1, tens = 10, hundreds = 100 ...
			ADD DX, AX			;Adds (digit * PLACEMENT-VALUE)s together. RECALL: 234 = (4 * 1) + (3 * 10) + (2 * 100) where 1,10,100 represent their PLACEMENT-VALUES
			MOV AX, 10				
			MUL BL				;Multiplies current PLACEMENT-VALUE by 10 to advance to the next PLACEMENT-VALUE.
			XCHG AX, BX			;Puts result from multiplication back to BX
			DEC CX				;Reduces count
			JMP CLOOP2			;Loop continues
			
XCLOOP2:	MOV AX, DX				;Moves converted value to AX
			
			POPF
			POP SI
			POP DX
			POP CX
			POP BX
			RET
CHAR2INTR ENDP
;End of Subroutine CHAR2INTR

END START
;                               \|||/                                            
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