How many symbols I can write in 1,2,4 bytes? asm

Question

I am studying asm, and I know that if I would like to take a number from keyboard, I can simple do this:

inputarea db 3 DUP(' '),'$' mov ah,0Ah mov dx,offset inputarea int 21h

In this case, I can write symbols until I reach 255. But there is a db(data byte) type, so in this case I can only write max 3 numbers which is correct to asm to execute it (123 , 100 and so on...). But If have Data Word, or DD types, how many symbols I can write which can be executed?

Hint: for example, If I have type 'data byte', so this will exlude memory of 1 byte. And there is able to store only 3 numbers. What about others types?

Andreas Fester · Accepted Answer · 2014-01-16 12:53:21Z

I know that if I would like to take a number from keyboard, I can simple do this: ...

No, its not that simple - you have to setup a transfer buffer correctly. Function 0ah reads from standard input and writes the characters it reads into a buffer, see Interrupts MS-DOS Function Calls (INT 21h), page 4:

count = 80 KEYBOARD STRUCT maxInput BYTE count ; max chars to input inputCount BYTE ? ; actual input count buffer BYTE count DUP(?) ; holds input chars KEYBOARD ENDS .data inputarea KEYBOARD <> .code mov ah, 0Ah mov dx, OFFSET inputarea int 21h

Then, you will end up with a string in the input buffer which you need to convert to a number.

another version I think is: inputarea db 3,?,3 DUP(' '). isn't it?
Yes, this should work also - the above structure basically expands to that

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