2_2_4_2.asm

find the first blank and store its addre

DATA 	SEGMENT
S		DB		'ABCDEFGHIJKLMNOPQRSTUVWXYZ$' 
LENTH	EQU		$-S	  
CHAR	DB		'Please enter a captial charater:$'
DATA 	ENDS

STACK 	SEGMENT
    
STACK 	ENDS

CODE 	SEGMENT
    	ASSUME 		CS:CODE,	DS:DATA,	SS:STACK

START		PROC
    	MOV 	AX,DATA
    	MOV 	DS,AX

	LEA		DX,CHAR
	MOV		AH,	09H
	INT		21H
    
	MOV		AH,01H
	INT		21H
    	LEA		SI,S
SCAN: 
    	CMP		AL,S[SI]
    	JZ		INSERT
    	INC		SI
    	JMP		SCAN
INSERT:	
	MOV		DX,SI
	MOV		SI,LENTH
	INC		SI
SEARCH:
	CMP		DX,SI
	JZ		ADDCHAR
	MOV		CL,S[SI-1]
	MOV		S[SI],CL
	DEC		SI
	JMP		SEARCH
ADDCHAR:
	INC		SI
	MOV		CL,S[SI-1]
	MOV		S[SI],CL
	LEA		DX,S
	MOV		AH,09H
	INT		21H
    	MOV 	AH,4CH
    	INT 		21H
START		ENDP
CODE 	ENDS
    	END 	START