TCPU/README.md

TCPU

Machine code interpreter written in pure C. Can execute programs up to 1 MEGABYTE (1048576 bytes) in size!!!

Building

1. Install cbuild
2. Install SDL3 and SDL3_image from package manager or source.

3. cbuild build_exec_dbg
   

Assembly language

Registers

name	code	size (bits)
rax	0x01	64
eax	0x02	32
ax	0x04	16
al	0x07	8
ah	0x08	8
rbx	0x11	64
ebx	0x12	32
bx	0x14	16
bl	0x17	8
bh	0x18	8
rcx	0x21	64
ecx	0x22	32
cx	0x24	16
cl	0x27	8
ch	0x28	8
rdx	0x31	64
edx	0x32	32
dx	0x34	16
dl	0x37	8
dh	0x38	8

Instructions

name	arguments	details
NOP		ignored instruction
EXIT		stop the program with exit code in eax
SYS		call system function
MOVC	dst_register, value	push constant value into dst_register
MOVR	dst_register, src_register	copy value from src_register to dst_register
ADD	dst_register, src_register	dst += src
SUB	dst_register, src_register	dst -= src
MUL	dst_register, src_register	dst *= src
DIV	dst_register, src_register	dst /= src
MOD	dst_register, src_register	dst %= src
EQ	dst_register, src_register	cmp_flag = dst == src
NE	dst_register, src_register	cmp_flag = dst != src
LT	dst_register, src_register	cmp_flag = dst < src
LE	dst_register, src_register	cmp_flag = dst <= src
GT	dst_register, src_register	cmp_flag = dst > src
GE	dst_register, src_register	cmp_flag = dst >= src
NOT	dst_register	dst = !dst
INV	dst_register	dst = ~dst
OR	dst_register, src_register	dst = dst | src
XOR	dst_register, src_register	dst = dst ^ src
AND	dst_register, src_register	dst = dst & src
JMP	dst_register	goto dst
JNZ	dst_register	if (cmp_flag != 0) goto dst
JZ	dst_register	if (cmp_flag == 0) goto dst

System functions

To call a system function you need to push values to registers and write SYS opcode. The return value of a function will will be avaliable in ax after call.

name	al	ah	rbx	ecx	details
read	0	file number	buffer pointer	buffer size	read data from file
write	1	file number	buffer pointer	buffer size	write data to file