GB Programming: Difference between revisions

 

Let's get started!

 

==A new world==

* A group of 64 bits is called a '''quadruple word''' or '''qword'''.

We will mostly be working with bytes, sometimes with words and rarely with nibbles. It is wery rare to work with other structures, so you may forget them if you will.

 

Now, let's talk about '''hexadecimal'''. It is '''base 16''', so we will be working with 16 symbols : 0 1 2 3 4 5 6 7 8 9 A B C D E F. Again, we will prepend hex numbers with a $ to differentiate them.

 

For the rest of this tutorial, we will mostly be using hexadecimal, but always remember the binary lying down below!

 

==A dip into technical information==

 

Notice that F and AF aren't usable anywhere. Actually, only a few instructions use them.

 

===Negative numbers===

 

For those wondering, ''ld a, ($6511)'' leaves ($6511) untouched.

 

==Flags==

* SCF sets it, and

* CCF inverts it.

 

==Manipulating data==

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These are often used to operate on cHunks of memory.

 

===Overflow===

 

Thus, the result is A equals 66 = %01000010, and the C flag is set.

 

===Register pairs and RAM===

ld ($C000), hl ; Save stack pointer

</pre>

 

===Good news===

 

Beware with the stack, even more when you're not coding your own game : everyone uses the stack ; even the CPU! (We're about to see how) The best practice to have is to leave the stack identical before and after your code. Otherwise, expect some crashes, yay!

 

==Control structures==

 

And this brings us to the next part!

 

===Conditionals===

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Four instructions can use conditionals : CALL, RET (these are coming in soon), JP and JR. JR has a handicap, though : it can only use the Z, NZ, C and NC conditions.

 

==Solutions to the exercises==

</pre>

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===Register pair and RAM===

|$00||$03||$4F||$06||$DF||$DE||$2A||$00||$FF||$01||$23||$34||$0E||$C0||$28||$BC

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==Credits==