The Instruction set

Those instructions with a '*' in the 'Flag' column will set the flag if they fail. Conditions for failure are given. Otherwise, the flag is cleared.

Instructions	Hex code	Flag	Action
nop_0	0x00		No operation. Used as in templates.
nop_1	0x01		No operation. Used as in templates.
or1	0x02		cx ^= 1
sh1	0x03		cx <<= 1
zero	0x04		cx = 0
if_cz	0x05		if (cx == 0) {execute the next instruction} else {skip it}
sub_ab	0x06		cx = ax - bx
sub_ac	0x07		ax = ax - cx
inc_a	0x08		ax ++
inc_b	0x09		bx ++
dec_c	0x0A		cx --
inc_c	0x0B		cx ++
push_ax	0x0C		stack[sp] = ax, sp = (sp + 1) mod stackSize
push_bx	0x0D		stack[sp] = bx, sp = (sp + 1) mod stackSize
push_cx	0x0E		stack[sp] = cx, sp = (sp + 1) mod stackSize
push_dx	0x0F		stack[sp] = dx, sp = (sp + 1) mod stackSize
pop_ax	0x10		sp = (sp + stackSize - 1) mod stackSize, ax = stack[sp]
pop_bx	0x11		sp = (sp + stackSize - 1) mod stackSize, bx = stack[sp]
pop_cx	0x12		sp = (sp + stackSize - 1) mod stackSize, cx = stack[sp]
pop_dx	0x13		sp = (sp + stackSize - 1) mod stackSize, dx = stack[sp]
jmp	0x14	*	Search for the complement to the template following the jmp instruction, looking both forward and back to a max distance of 1024 instructions. If found, set the instruction pointer to the instruction following the found template complement. On failure, set the flag and set the instruction pointer to the instruction following the the template.
jumpb	0x15	*	Search for the complement to the template following the jmp instruction, looking backwards to a max distance of 1024 instructions. If found, set the instruction pointer to the instruction following the found template complement. On failure, set the flag and set the instruction pointer to the instruction following the the template.
call	0x16	*	Search for the complement to the template following the jmp instruction, looking both ways to a max distance of 1024 instructions. If found, push the current instruction pointer onto the stack, and set the instruction pointer to the instruction following the found template complement. If no template follows the call instruction, On failure, set the flag and set the instruction pointer to the instruction following the the template.
ret	0x17		Decrement the stack pointer. Set the instruction pointer to the address from the stack.
mov_cd	0x18		dx = cx
mov_ab	0x19		bx = ax
mov_iab	0x1A	*	Copy the instruction in the soup pointed to by the address in the bx register to the address in the ax register. Fails and sets the flag if the address pointed to by ax is not free space, the current creature, or its current offspring (if any).
adr	0x1B	*	Search both ways, up to distance of 1024 instructions, for the complement to the template following the adr instruction. If found, put the address of the instruction following the found template into ax, and set cx to the length of the template. On failure, set the flag.
adrb	0x1C	*	Search backwards, up to distance of 1024 instructions, for the complement to the template following the adb instruction. If found, put the address of the instruction following the found template into ax, and set cx to the length of the template. On failure, set the flag.
adrf	0x1D	*	Search forwards, up to distance of 1024 instructions, for the complement to the template following the adb instruction. If found, put the address of the instruction following the found template into ax, and set cx to the length of the template. On failure, set the flag.
mal	0x1E	*	Allocate a daughter cell, of the size given by the dx register, and a location goverened by the ax register and the current offspring allocation scheme. On allocation, the address of the allocated cell is returned in the ax register of the parent. Fails if this creature already has an 'embryo' (offspring for which the div instruction has not yet been executed, if the size in dx is less than the current minimum size (12 instructions) or more than some multiple of the parent's size (3 times). Also fails if space could not be allocated for the offspring.
divide	0x1F	*	Separate from the current offspring, which is then given autonomy, and entered into slicer and reaper queues. Instruction pointer of the daughter is set to its first instruction. Offspring registers are either zeroed, or copied from the parent (depending on the settings). Fails if there is not current offspring, or if less than some proportion (currently 0.5) of the daughter has been filled by copy (mov_iab) instructions from the parent.

For information about how to compile your own creatures, see the page on assembling.