how to store strings in 8086 - string

Question

Im using emu8086.
For example i have a macro called 'store' which takes a string and stores it in an array, how do i do that?
sample code:
arrayStr db 30 dup(' ')
store "qwerty"
store MACRO str
*some code here which stores str into arrayStr*
endm
Most examples i found on the internet revolve around already having the string stored in a variable (ex. string db (some string here)) but i want something where the variables get initialized empty first.

Answer 1

Do you want to change a variable at runtime? In this case take a look at the PRINT-macro in emu8086.inc. A few changes and you've got a STORE-macro:
store MACRO str
LOCAL skip_data, endloop, repeat, localdata
jmp skip_data ; Jump over data
localdata db str, '$', 0 ; Store the macro-argument with terminators
skip_data:
mov si, OFFSET localdata
mov di, OFFSET msg
repeat: ; Loop to store the string
cmp byte ptr [si], 0 ; End of string?
je endloop ; Yes: end of loop
movsb ; No: Copy one byte from DS:SI to ES:DI, inc SI & DI
jmp repeat ; Once more
endloop:
ENDM
crlf MACRO
LOCAL skip_data, localdata
jmp skip_data
localdata db 13, 10, '$'
skip_data:
mov dx, offset localdata
mov ah, 09h
int 21h
ENDM
ORG 100h
mov dx, OFFSET msg
mov ah, 09h
int 21h
crlf
store "Hello!"
mov dx, OFFSET msg
mov ah, 09h
int 21h
crlf
store "Good Bye."
mov dx, OFFSET msg
mov ah, 09h
int 21h
mov ax, 4C00h
int 21h
msg db "Hello, World!", '$'

Answer 2

It depends on, what you want to do with the string
Here are some examples:
ASCIZ-String
The string ends with a zero-byte.
The advantage is that everytime the CPU loads a single byte from the RAM the zero-flag is set if the end of the string is reached.
The disadvantage is that the string mustn't contain another zero-byte. Otherwise the program would interprete an earlier zero-byte as the end of the string.
String input from DOS-Function Readln (int 21h/ ah=0ah)
The first byte defines, how long the string inputted by the user could be maximally. The effective length is defined in the second byte. The rest contains the string.
String which is ready to be outputted using WriteLn (int 21h/ ah=09h)
The string ends with a dollar-sign (ASCII 36).
The advantage is that your programm can output the string using a single function (int 21h/ ah=09h).
The disadvantage is that the string mustn't contain another dollar-sign. Otherwise the program would interprete an earlier dollar-sign as the end of the string.
String whose length is defined in a word/byte at the beginning of the String
Unformatted String
You don't have to save the length in a variable nor marking the end, if you save the length to a constant which you can put in a register (e.g. in CX)