diff --git a/src/uxn.c b/src/uxn.c
index 870a361..d46ba0a 100644
--- a/src/uxn.c
+++ b/src/uxn.c
@@ -13,15 +13,19 @@ WITH REGARD TO THIS SOFTWARE.
 
 /* clang-format off */
 
-#define PUSH8(s, x) { if(s->ptr == 0xff) { errcode = 2; goto err; } s->dat[s->ptr++] = (x); }
-#define PUSH16(s, x) { if((j = s->ptr) >= 0xfe) { errcode = 2; goto err; } k = (x); s->dat[j] = k >> 8; s->dat[j + 1] = k; s->ptr = j + 2; }
+/*	a,b,c: general use.  bs: byte/short bool. src, dst: stack ptrs, swapped in return mode.
+	pc: program counter. sp: ptr to src stack ptr. kptr: "keep" mode copy of src stack ptr.
+	x,y: macro in params. d: macro in device. j,k,dev: macro temp variables. o: macro out param. */
+
+#define HALT(c) { return uxn_halt(u, instr, (c), pc - 1); }
+#define PUSH8(s, x) { if(s->ptr == 0xff) HALT(2) s->dat[s->ptr++] = (x); }
+#define PUSH16(s, x) { if((j = s->ptr) >= 0xfe) HALT(2) k = (x); s->dat[j] = k >> 8; s->dat[j + 1] = k; s->ptr = j + 2; }
 #define PUSH(s, x) { if(bs) { PUSH16(s, (x)) } else { PUSH8(s, (x)) } }
-#define POP8(o) { if(!(j = *sp)) { errcode = 1; goto err; } o = (Uint16)src->dat[--j]; *sp = j; }
-#define POP16(o) { if((j = *sp) <= 1) { errcode = 1; goto err; } o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }
+#define POP8(o) { if(!(j = *sp)) HALT(1) o = (Uint16)src->dat[--j]; *sp = j; }
+#define POP16(o) { if((j = *sp) <= 1) HALT(1) o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }
 #define POP(o) { if(bs) { POP16(o) } else { POP8(o) } }
 #define POKE(x, y) { if(bs) { u->ram[(x)] = (y) >> 8; u->ram[(x) + 1] = (y); } else { u->ram[(x)] = y; } }
-#define PEEK16(o, x) { o = (u->ram[(x)] << 8) + u->ram[(x) + 1]; }
-#define PEEK(o, x) { if(bs) { PEEK16(o, x) } else { o = u->ram[(x)]; } }
+#define PEEK(o, x) { if(bs) { o = (u->ram[(x)] << 8) + u->ram[(x) + 1]; } else { o = u->ram[(x)]; } }
 #define DEVR(o, x) { o = u->dei(u, x); if (bs) o = (o << 8) + u->dei(u, ((x) + 1) & 0xFF); }
 #define DEVW(x, y) { if (bs) { u->deo(u, (x), (y) >> 8); u->deo(u, ((x) + 1) & 0xFF, (y)); } else { u->deo(u, x, (y)); } }
 #define JUMP(x) { if(bs) pc = (x); else pc += (Sint8)(x); }
@@ -29,28 +33,20 @@ WITH REGARD TO THIS SOFTWARE.
 int
 uxn_eval(Uxn *u, Uint16 pc)
 {
-	unsigned int a, b, c, j, k, bs, instr, errcode;
+	unsigned int a, b, c, j, k, bs, instr;
 	Uint8 kptr, *sp;
 	Stack *src, *dst;
 	if(!pc || u->dev[0x0f]) return 0;
 	while((instr = u->ram[pc++])) {
 		/* Return Mode */
-		if(instr & 0x40) {
-			src = u->rst; dst = u->wst;
-		} else {
-			src = u->wst; dst = u->rst;
-		}
+		if(instr & 0x40) { src = u->rst; dst = u->wst; }
+		else { src = u->wst; dst = u->rst; }
 		/* Keep Mode */
-		if(instr & 0x80) {
-			kptr = src->ptr;
-			sp = &kptr;
-		} else {
-			sp = &src->ptr;
-		}
+		if(instr & 0x80) { kptr = src->ptr; sp = &kptr; }
+		else sp = &src->ptr;
 		/* Short Mode */
 		bs = instr & 0x20 ? 1 : 0;
 		switch(instr & 0x1f) {
-		/* Stack */
 		case 0x00: /* LIT */ PEEK(a, pc) PUSH(src, a) pc += 1 + bs; break;
 		case 0x01: /* INC */ POP(a) PUSH(src, a + 1) break;
 		case 0x02: /* POP */ POP(a) break;
@@ -59,7 +55,6 @@ uxn_eval(Uxn *u, Uint16 pc)
 		case 0x05: /* ROT */ POP(a) POP(b) POP(c) PUSH(src, b) PUSH(src, a) PUSH(src, c) break;
 		case 0x06: /* DUP */ POP(a) PUSH(src, a) PUSH(src, a) break;
 		case 0x07: /* OVR */ POP(a) POP(b) PUSH(src, b) PUSH(src, a) PUSH(src, b) break;
-		/* Logic */
 		case 0x08: /* EQU */ POP(a) POP(b) PUSH8(src, b == a) break;
 		case 0x09: /* NEQ */ POP(a) POP(b) PUSH8(src, b != a) break;
 		case 0x0a: /* GTH */ POP(a) POP(b) PUSH8(src, b > a) break;
@@ -68,7 +63,6 @@ uxn_eval(Uxn *u, Uint16 pc)
 		case 0x0d: /* JCN */ POP(a) POP8(b) if(b) JUMP(a) break;
 		case 0x0e: /* JSR */ POP(a) PUSH16(dst, pc) JUMP(a) break;
 		case 0x0f: /* STH */ POP(a) PUSH(dst, a) break;
-		/* Memory */
 		case 0x10: /* LDZ */ POP8(a) PEEK(b, a) PUSH(src, b) break;
 		case 0x11: /* STZ */ POP8(a) POP(b) POKE(a, b) break;
 		case 0x12: /* LDR */ POP8(a) PEEK(b, pc + (Sint8)a) PUSH(src, b) break;
@@ -77,11 +71,10 @@ uxn_eval(Uxn *u, Uint16 pc)
 		case 0x15: /* STA */ POP16(a) POP(b) POKE(a, b) break;
 		case 0x16: /* DEI */ POP8(a) DEVR(b, a) PUSH(src, b) break;
 		case 0x17: /* DEO */ POP8(a) POP(b) DEVW(a, b) break;
-		/* Arithmetic */
 		case 0x18: /* ADD */ POP(a) POP(b) PUSH(src, b + a) break;
 		case 0x19: /* SUB */ POP(a) POP(b) PUSH(src, b - a) break;
 		case 0x1a: /* MUL */ POP(a) POP(b) PUSH(src, (Uint32)b * a) break;
-		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) { errcode = 3; goto err; } PUSH(src, b / a) break;
+		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) HALT(3) PUSH(src, b / a) break;
 		case 0x1c: /* AND */ POP(a) POP(b) PUSH(src, b & a) break;
 		case 0x1d: /* ORA */ POP(a) POP(b) PUSH(src, b | a) break;
 		case 0x1e: /* EOR */ POP(a) POP(b) PUSH(src, b ^ a) break;
@@ -89,23 +82,21 @@ uxn_eval(Uxn *u, Uint16 pc)
 		}
 	}
 	return 1;
-err:
-	return uxn_halt(u, instr, errcode, pc - 1);
 }
 
 /* clang-format on */
 
 int
-uxn_boot(Uxn *u, Uint8 *ram, Uint8 (*dei)(struct Uxn *, Uint8), void (*deo)(struct Uxn *, Uint8, Uint8))
+uxn_boot(Uxn *u, Uint8 *ram, Dei *dei, Deo *deo)
 {
 	Uint32 i;
 	char *cptr = (char *)u;
 	for(i = 0; i < sizeof(*u); i++)
 		cptr[i] = 0x00;
-	u->ram = ram;
 	u->wst = (Stack *)(ram + 0x10000);
 	u->rst = (Stack *)(ram + 0x10100);
 	u->dev = (Uint8 *)(ram + 0x10200);
+	u->ram = ram;
 	u->dei = dei;
 	u->deo = deo;
 	return 1;