# vc4

**virtual computer 4** (see [vc3](https://git.sfja.dk/sfja/vc4) and [vc2](https://github.com/simonFJ20/vc2))

a computer-emulator with custom architecture, and some stuff to write and run software on it.

## goals

- [ ] assemble program on host
- [ ] run program from host
- [ ] run program from emulated disk
- [ ] output to monitor device
- [ ] input from keyboard device
- [ ] command shell
- [ ] read/write files on emulated disk
- [ ] host/vm file share
- [ ] run programs from emulated disk
- [ ] edit text files
- [ ] assemble program on vm

## isa

- 16-bit instruction set
- big endian

### registers

```
r0      accumulator / return value
r1
r2
r3
r4
r5
r6
sp      stack pointer
bp      base pointer
```

### instructions

```
r   = register
i16 = 16-bit immediate
m   = memory [r/i16]

nop
hlt
jmp     r/i16
jnz     r/i16
cmp     r/i16
mov     r/i16/m r
mov     r       r/i16/m
movb    m       r
movb    r       m
in      r/i16
out     r/i16   r/i16
call    r/i16
ret
lit     r/i16
int     i8

or      r       r/i16
xor     r       r/i16
and     r       r/i16
shl     r       r/i16
rshl    r       r/i16
shr     r       r/i16
rshr    r       r/i16
add     r       r/i16
sub     r       r/i16
rsub    r       r/i16
mul     r       r/i16
imul    r       r/i16
div     r       r/i16
idiv    r       r/i16
mod     r       r/i16
rmod    r       r/i16
```