CODEWITHSUNDEEP
fileassemblybyte
user1624667
user1624667

Reputation: 231

Read File assembly language

I'm writing this file in assembly language and it reads a file which is 64,000 bytes long. I don't want to store it in RAM so I need to make it so that it reads one byte, manipulates the data, then store the next byte at the same address.

Any Ideas?

I am running on a MS-DOS boot disk on windows XP hardware (I don't know the specs) when ever I run it where I store the 64,000 I get an EMM error telling me I need to reboot.

Upvotes: 0

Views: 1116

Answers (1)

Alexey Frunze
Alexey Frunze

Reputation: 62106

You can use DOS int 21h function 48h to allocate 64000 bytes of memory. It allocates memory in multiples of 16 bytes, so you pass it 64000/16=4000 in BX.

On return from that function AX will contain the segment of the allocated block, which you will have to load into a segment register (DS, ES, FS or GS) before accessing that block. If you load it into a segment register other than DS, you will need to prefix the instructions accessing the block with the segment override prefix, like so:

mov [es:0], al -- stores AL to the very first byte of the block (the block's segment is in ES).

When you're done using the allocated memory, you free it using function 49h.

Upvotes: 3

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