Opcodes

[cam875]

Is there some documentation that shows what all the different operations and stuff represent in hex or binary

like mov = 10011101 or w.e it is

its for 80386 architecure btw.

thanks in advance.

[Salem]

Google "8086 processor reference manual"

[cam875]

I did that and the documentation just tells me how to program like how to use mov and add and all that and registers but I am looking to write my own little assembler and need to know the machine code versions so it can be translated to byte code. maybe u know a better thing i should be looking for or sometin. thanks in advance.

[Salem]

Keep looking, some of them tell you how opcodes are encoded at the bit level.

[cam875]

shit this is the hardest thing to find ever Ive now spent around 3 hours of just straight searching for this I just want to know all the operations and everything in hex or binary. You would think this would be pretty easy to find. Should i be looking on intels website or something?

[Salem]

http://www.x86.org/

[cam875]

http://developer.intel.com/design/pentium/manuals/24319101.pdf

is that the documentation i should be looking at particularly at the opcode map which is very confusing lol. Also can u program 8 bit on a 32 bit cpu.

[Salem]

Yeah, pretty much all of that.

[cam875]

ok i actually understand the opcode map now and i am able to get hex code out of it which is great but what i dont understand is if a memory adress represents a byte inside your ram than how can it store a 4byte value (32 bit) at one adresss?

[Salem]

It uses 4 consecutive addresses.
All the addresses you specify are the start address, then the length modifier tells the processor whether to fetch 1, 2, or 4 bytes.

[cam875]

ok makes sense but i found another problem, when i open my binary files up in a hex editor from a line where i specify a memory address it always has 2 hex values for it. like 00 00 for the memroy address 0 why doesnt it just put 00 that seems like a waste of space

[cam875]

so if i make a dword at memory adress 0 that means that 0,1,2,3 adresses are now taken and if i write data to any of biaccidently them I am overwriting other data that I previously stored? I am assuming that good programming languages take care of this so you dont overwrite your data?

[Salem]

> them I am overwriting other data that I previously stored?
Yes.

> I am assuming that good programming languages take care of this so you dont overwrite your data?
Also correct.

[cam875]

if I am writing my own operating system how Do i no which memory address my bootloader is being loaded into initially when it is read off of the floppy disk. Is the initial bootloader loaded to memory address 0 or something?

[Salem]

http://www.nondot.org/sabre/os/articles

[cam875]

ok thanks, i am a little confused as to how input and output works on a computer with interrupts could u explain it a bit if u dont mind or point me in the right direction. Gimme a little explanation for an example like if I pressed the a key on my keyboard what happens and if I wanted to draw to the pixel 0,0 and colour it red or something.

[cam875]

i just realized this, why dont they make it so you can fetch 24 bits ot 3 bytes and make the cpu register able to store and manipulate them too. Wouldnt it be more sufficient having the power to utilize 1,2,3, or 4 bytes.