8086 Write a program that takes one string from the input and inserts white space between every two letters - nasm

Question

8086 Write a program that takes one string from the input and inserts white space between every two letters
using nasm and MSDOS
i have do following code but it is not working
start:
mov ax,data
mov ds, ax
mov es, ax
mov cx, size;cx will contain size,we need it to
; check if we have got 10 inputs from key board
lea dx, Enter_string;it will display a text on screen to enter text
mov ah, 9
int 21h
call get_string;input string from keyboard
mov ax, 4ch;terminating
int 21h
get_string:
mov si, 0; si will be used as index
mov bx, offset string
get_char:
mov ah, 1; get a char from keyboard
int 21h
mov [bx][si], al; saving input in string
inc si
cmp si,cx;if si=7 than, no need to take more input
jne get_char
ret

Answer 1

. You should prefer the simplicity of .COM programs while learning. They already start with all the segment registers pointing to the program.
. The DOS exit function expects the function number in AH.
. On NASM you don't use mov bx, offset string. Just write mov bx, string.
. It's easy to combine the tasks of inputting a string and interjecting space characters. See below code:
org 256 ;.COM programs have CS=DS=ES=SS
start:
mov cx, size ;cx will contain size,we need it to
; check if we have got 10 inputs from key board
mov dx, Enter_string ;it will display a text on screen to enter text
mov ah, 9
int 21h
call get_string ;input string from keyboard
mov ax, 4C00h ;terminating
int 21h
get_string:
push cx
mov si, 0 ; si will be used as index
get_char:
mov ah, 1 ; get a char from keyboard
int 21h
mov ah, " "
mov [string+si], ax ; saving input in string PLUS THE SPACE CHARACTER
add si, 2
dec cx ;if si=7 than, no need to take more input
jnz get_char
pop cx
ret
Remember that you don't actually need the last space character. Just overwrite it with the string terminator that you normally would add to this string!