diff --git a/Makefile b/Makefile
index 1b03c2d..f86b627 100644
--- a/Makefile
+++ b/Makefile
@@ -8,9 +8,13 @@ kpc:
 	@cd pc && make --no-print-directory
 
 kas: kpc as/k-as.py as/regs.lst as/testfile.asm
-	@cp pc/instrs.lst as
+	@cp pc/instrs/instrs.lst as
+	@rm -f pc/instrs/instrs.lst
 
 test: kas
 	@cd as && ./k-as.py testfile.asm 0x100000 testout.out
 	@pc/k.exe as/testout.out
 
+disasm: kas
+	@cd as && ./k-as.py testfile.asm 0x100000 testout.out
+	@pc/k.exe as/testout.out -d
diff --git a/as/k-as.py b/as/k-as.py
index 4b7402b..642da44 100755
--- a/as/k-as.py
+++ b/as/k-as.py
@@ -13,11 +13,9 @@ if len(sys.argv) != 4:
                     .format(sys.argv[0]))
     sys.exit(1)
 
-# TemporaryFile(mode='w+')
-instrs = open("testfile.out.1", "w+")
-
-b_data = open("testfile.out.2", "w+b")
-b_text = open("testfile.out.3", "w+b")
+instrs = open("{}.instr".format(sys.argv[3]), "w+")
+b_data = open("{}.data".format(sys.argv[3]), "w+b")
+b_text = open("{}.text".format(sys.argv[3]), "w+b")
 
 lst_regs = open("regs.lst")
 lst_instrs = open("instrs.lst")
@@ -69,7 +67,7 @@ pdata_pad = 0
 
 def name_valid(name):
     for c in name.lower():
-        if not(c in 'abcdefghijklmnopqrstuvwxyz0123456789[$%._+]='):
+        if not(c in 'abcdefghijklmnopqrstuvwxyz0123456789[$._+]='):
             print("BAD '{}'".format(c))
             return False
     return True
@@ -93,27 +91,59 @@ def parse_preproc(line):
 
     tok = line.split(' ', 2)
 
-    for word in tok:
-        if not name_valid(word):
-            print("Invalid token in line: {}".format(line))
-            return
+    #for word in tok:
+    #    if not name_valid(word):
+    #        print("Invalid token in line: {}".format(line))
+    #        return
 
-    if tok[0] == 'def':
+    # preprocessor
+    if len(tok) > 1 and tok[1] == ':=':
         if len(tok) < 3:
             print("Invalid format: {}".format(line))
-        else:
-            pdefs[tok[1]] = tok[2]
+            leave()
+            sys.exit(1)
+        pdefs[tok[0]] = tok[2]
         return
     
     # .data
     if len(tok) > 1 and tok[1] == '=':
         if len(tok) < 3:
             print("Invalid format: {}".format(line))
-        else:
+            leave()
+            sys.exit(1)
+
+        if is_number(tok[2]):
             plabels_data[tok[0]] = pdata
-            written = b_data.write(int(tok[2]).to_bytes(8, byteorder='little', signed=False))
+            written = b_data.write(int(tok[2], base=0).to_bytes(8, byteorder='little', signed=False))
             assert(written == 8)
             pdata += written
+
+        elif tok[2][0] == "'":
+            s = tok[2].strip()
+            assert(s[-1] == "'")
+            
+            s = s[1:-1]
+            assert(not "'" in s)
+
+            plabels_data[tok[0]] = pdata
+            pdefs[tok[0] + "_len"] = str(len(s))
+
+            for c in s:
+                written = b_data.write(ord(c).to_bytes(1, byteorder='little', signed=False))
+                assert(written == 1)
+                pdata += 1
+                
+            # align
+            for i in range(8 - len(s) % 8):
+                written = b_data.write(int(0).to_bytes(1, byteorder='little', signed=False))
+                assert(written == 1)
+                pdata += 1
+        
+        else:
+            print("Invalid format: {}".format(line))
+            leave()
+            sys.exit(1)
+
         return
     
     print("Unrecognized directive: {}".format(line))
@@ -205,8 +235,17 @@ def is_number(s):
     return True
    
 def parse_instr(line):
+    # instrs.write(hex(ptext))
     tok = line.split(' ')
     fellthrough = False
+
+    size = 2
+
+    if tok[0] == "rep":
+        instrs.write("%rep ")
+        tok = tok[1:]
+        size += 2
+    
     instr_name = tok[0]
     instr_args = ''
 
@@ -214,8 +253,9 @@ def parse_instr(line):
         instrs.write("{}".format(instr_name))
         return 2 # instruction
 
-    size = 2
-    for word in line.split(' ')[1:]:
+    tok = tok[1:]
+
+    for word in tok:
         instr_args += ' '
 
         pref = None
@@ -226,7 +266,7 @@ def parse_instr(line):
                 pref = "%b"
             elif word[0] == 'w':
                 pref = "%w"
-            elif word[0] == 'l':
+            elif word[0] == 'l' or word[0] == 'd':
                 pref = "%l"
             elif word[0] == 'q':
                 pref = "%q"
@@ -254,14 +294,15 @@ def parse_instr(line):
                 instr_args += "off "
                 
                 assert(len(word) > 3)
-                assert(word[2] == '+' or word[3] == '+')
-
-                if word[2] == '+':
-                    # r8, k0, etc
-                    instr_args += "{} {}".format(word[3:], word[:2])
-                else:
-                    # rax, cr0, etc
-                    instr_args += "{} {}".format(word[4:], word[:3])
+                
+                reg, off = word.strip().split('+', 1)
+                reg = reg.strip()
+                off = off.strip()
+                
+                print(reg)
+                print(off)
+                
+                instr_args += "{} {}".format(off, reg)
 
                 continue
             
@@ -293,7 +334,7 @@ def parse_instr(line):
             continue
         
         # it's a label (a 64-bit immediate)
-        # +2 for A_IMM16, +2 for immediate
+        # +2 for A_IMM64, +8 for immediate
         size += 2 + 8
         if not fellthrough:
             instr_name += "_i"
@@ -320,11 +361,15 @@ special_syms = {
     "%imm16": 0x7772,
     "%imm32": 0x7774,
     "%imm64": 0x7778,
+    
+    "%rep": 0x8000
 }
 
 def gentext():
     instrs.seek(0)
-    text_start = 0x100000
+    text_start = 0 # 0x100000
+    data_start = text_start + ptext
+    data_start += (8 - data_start % 8)
 
     for _, line in enumerate(instrs):
         tok = line.strip().split(' ')
@@ -342,12 +387,11 @@ def gentext():
 
             if word in plabels_text:
                 addr = text_start + plabels_text[word]
-                print(addr.to_bytes(8, byteorder='big', signed=False))
-                b_text.write(addr.to_bytes(8, byteorder='big', signed=False))
+                b_text.write(addr.to_bytes(8, byteorder='little', signed=False))
                 continue
 
             if word in plabels_data:
-                addr = text_start + plabels_data[word] + ptext + pdata_pad
+                addr = data_start + plabels_data[word] + pdata_pad
                 b_text.write(addr.to_bytes(8, byteorder='little', signed=False))
                 continue
 
@@ -358,6 +402,8 @@ def gentext():
                     lastimm = 4
                 elif word == "%imm64":
                     lastimm = 8
+                elif word[2:] == "off" and word[0] == '%':
+                    lastimm = 2
                 b_text.write(special_syms[word].to_bytes(2, byteorder='little', signed=False))
                 continue
             
@@ -375,6 +421,12 @@ def genout():
     b_text.seek(0)
     b_data.seek(0)
     b_out.write(b_text.read())
+
+    data_align = (8 - ptext % 8)
+    
+    for i in range(data_align):
+        b_out.write(int(0).to_bytes(1, byteorder='little', signed=False))
+
     b_out.write(b_data.read())
 
 #-------------------------------------------------------------------------------
diff --git a/as/k-as.py.text b/as/k-as.py.text
new file mode 100644
index 0000000..cdc4e1a
Binary files /dev/null and b/as/k-as.py.text differ
diff --git a/as/regs.lst b/as/regs.lst
index fc2caad..c824489 100644
--- a/as/regs.lst
+++ b/as/regs.lst
@@ -1,28 +1,32 @@
 inv
+rip
+flg
+rbp
+rsp
 rax
 rbx
 rcx
 rdx
+rsx
+rbi
 rdi
 rsi
-rbp
-rsp
-r8
-r9
-r10
-r11
-r12
-r13
-r14
-r15
-k0
-k1
-k2
-k3
-k4
-k5
-k6
-k7
+nx0
+nx1
+nx2
+nx3
+nx4
+nx5
+nx6
+nx7
+ax0
+ax1
+ax2
+ax3
+ax4
+ax5
+ax6
+ax7
 cr0
 cr1
 cr2
@@ -31,5 +35,11 @@ cr4
 cr5
 cr6
 cr7
-rip
-flg
+sa0
+sa1
+sa2
+sa3
+sa4
+sa5
+sa6
+sa7
diff --git a/as/testfile.asm b/as/testfile.asm
index ec92e5a..187f3af 100644
--- a/as/testfile.asm
+++ b/as/testfile.asm
@@ -1,13 +1,35 @@
 # Test assembly file
 # Wololo!
 
-def y 4
+hw = 'Hello World'
+
+main:
+    ; This comment is successfully ignored
+    mov rbp, 0x200000
+    mov rsp, rbp
+    
+    mov ax0, hw
+    mov ax1, hw_len
+    call print
 
-label1:
-    call label2
     stop
 
-label2:
-    add rax, 1
+print:
+    enter
+
+    mov rcx, ax1
+    rep call .pch1
+
+    leave
+    ret
+
+.pch1:
+    test b[ax0], b[ax0]
+    jnz .pch2
+    ret
+
+.pch2:
+    prn b[ax0]
+    inc ax0
     ret
 
diff --git a/pc/Makefile b/pc/Makefile
index 3270bc4..e59f9f6 100644
--- a/pc/Makefile
+++ b/pc/Makefile
@@ -3,23 +3,25 @@
 
 all: k.exe
 
-src = instrs.c decd.c main.c regs.c dump.c jumps.c except.c disdec.c mem.c
+src = instrs/instrs.c decd.c main.c regs.c dump.c \
+      instrs/jumps.c except.c disd.c mem.c instrs/logic.c \
+      instrs/stack.c instrs/super.c instrs/arith.c
 
 obj = $(patsubst %.c,%.o,$(src))
 
 %.o: %.c i_arch.h *.h $(src)
-	@gcc -O2 -Wall -c $< -o $@
+	@gcc -O2 -g -Wall -c $< -o $@
 
-i_arch.h: INSTRS instrs.py
-	@python3 instrs.py
+i_arch.h: instrs/INSTRS instrs/arch_i.py
+	@cd instrs && python3 arch_i.py
 
 .PHONY: clean
 
 clean:
 	@rm *.o
 
-k.exe: $(obj) i_arch.h INSTRS instrs.py
+k.exe: $(obj) i_arch.h
 	@gcc -O2 -Wall $(obj) -o k.exe
-	@rm arch_i.h
-	@rm *.o
+	@rm instrs/arch_i.h
+	@rm *.o */*.o
 
diff --git a/pc/arch.h b/pc/arch.h
index fd0377f..a2f3c44 100644
--- a/pc/arch.h
+++ b/pc/arch.h
@@ -1,6 +1,7 @@
 // The OS/K Team licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -26,50 +27,6 @@ typedef struct instr_t      instr_t;
 typedef struct acc_t        acc_t;
 typedef struct arch_t       arch_t;
 
-enum
-{
-    INV,
-    RAX, RBX, RCX, RDX, RDI, RSI, RBP, RSP,
-    R8,  R9,  R10, R11, R12, R13, R14, R15,
-    K0,  K1,  K2,  K3,  K4,  K5,  K6,  K7,
-    CR0, CR1, CR2, CR3, CR4, CR5, CR6, CR7,
-    RIP, FLG,
-
-    NREGS
-};
-
-enum 
-{
-    GPR = 1 << 0,   // General
-    CTL = 1 << 1,   // Control
-    SEG = 1 << 2,   // Segment
-    RES = 1 << 8,   // Reserved for insternal use
-    SYS = 1 << 9,   // Reserved for supervisor mode
-};
-
-// FLG register
-enum
-{
-    CF = 1 << 0,        // Carry flag
-    PF = 1 << 1,        // Parity flag
-    AC = 1 << 2,        // Auxiliary flag
-    ZF = 1 << 3,        // Zero flag
-    OV = 1 << 4,        // Overflow flag
-    DF = 1 << 5,        // Direction flag
-    SF = 1 << 6,        // Sign flag
-    
-    UF = 1 << 16,       // User-mode flag
-    IF = 1 << 17,       // Interrupts enable flag
-};
-
-struct reg_t
-{
-    char   *name;
-    char   *desc;
-    ulong   val;
-    ulong   flags;
-};
-
 // A_REG is implicit
 // A_MEM denotes a memory access
 // A_OFF is A_MEM but a 16-bit offset is expected immediatly next
@@ -104,11 +61,12 @@ enum
 struct acc_t
 {
     bool mem;
-    uint len;
-    uint type;
-
-    ulong val;
+    uint mlen;
     short off;
+
+    uint type;
+    uint ilen;
+    ulong val;
 };
 
 enum { NOPREF, PREF_REP=0x8000, PREF_LOCK, NPREFS };
@@ -145,6 +103,12 @@ struct ctx_t
     FILE *disf;
 };
 
+static inline ushort bswap16(ushort u)
+{ return ((u<<8) | (u>>8)); }
+
+static inline char getmempref(ushort len)
+{ return (len==1?'b':(len==2?'w':(len==4?'l':(len==8?'q':'x')))); }
+
 enum
 {
     E_SHT,          // Shutdown instruction
@@ -158,7 +122,7 @@ enum
 };
 
 void dumpregs(ctx_t *);
-void dumpinstr(ctx_t *, ulong, ushort, acc_t *, acc_t *);
+void dumpinstr(ctx_t *, ulong, uint, ushort, acc_t *, acc_t *);
 void dumpmem(ctx_t *, ulong, ulong);
 void dumpfwstack(ctx_t *);
 
@@ -188,5 +152,9 @@ void writemem32(ctx_t *, ulong val, ulong addr);
 void writemem64(ctx_t *, ulong val, ulong addr);
 void writemem(ctx_t *, ulong val, ulong addr, uint len);
 
-#include "arch_i.h"
+#include "regs.h"
+#include "instrs/arch_i.h"
+
+extern reg_t arch_r[NREGS];
+extern instr_t arch_i[NINSTRS];
 
diff --git a/pc/decd.c b/pc/decd.c
index 21b0b01..c7e1061 100644
--- a/pc/decd.c
+++ b/pc/decd.c
@@ -36,13 +36,13 @@ static void scan_param(ctx_t *ctx, acc_t *p)
     if (A_IS_MEM(c)) {
         p->mem = 1;
         p->off = 0;
-        p->len = c & 0xF;
+        p->mlen = c & 0xF;
         c = ctx->get(ctx);
     }
     
     else if (A_IS_OFF(c)) {
         p->mem = 1;
-        p->len = c & 0xF;
+        p->mlen = c & 0xF;
         p->off = (short)ctx->get(ctx);
         c = ctx->get(ctx);
     }
@@ -59,13 +59,15 @@ static void scan_param(ctx_t *ctx, acc_t *p)
     p->val = c;
         
     if (p->type == A_IMM32) {
-        p->val = (p->val << 16) | ctx->get(ctx);
+        p->ilen = 4;
+        p->val = p->val | ((ulong)ctx->get(ctx) << 16);
     }
         
     else if (p->type == A_IMM64) {
-        p->val = (p->val << 16) | ctx->get(ctx);
-        p->val = (p->val << 16) | ctx->get(ctx);
-        p->val = (p->val << 16) | ctx->get(ctx);
+        p->ilen = 8;
+        p->val = p->val | ((ulong)ctx->get(ctx) << 16);
+        p->val = p->val | ((ulong)ctx->get(ctx) << 32);
+        p->val = p->val | ((ulong)ctx->get(ctx) << 48);
     }
     
     else if (p->type == A_REG) {
@@ -90,11 +92,15 @@ void disasm(ctx_t *ctx)
     instr_t *i;
     acc_t p1 = { 0 }, p2 = { 0 };
 
+    uint rep = 0;
     ulong rip = ctx->r[RIP].val;
     ushort c = ctx->get(ctx);
 
     if (ISPREF(c)) {
-        // nothing for now
+        if (c == PREF_REP) {
+            rep = 1;
+            c = ctx->get(ctx);
+        }
     }
     
     else if (!ISINSTR(c)) {
@@ -111,10 +117,18 @@ void disasm(ctx_t *ctx)
         }
     }
 
-    dumpinstr(ctx, rip, c, &p1, &p2);
+    dumpinstr(ctx, rip, rep, c, &p1, &p2);
     
 #ifndef _NEED_DISASM
+
+do_rep:
     i->func(ctx, &p1, &p2);
+
+    if (rep && ctx->r[RCX].val > 0) {
+        ctx->r[RCX].val--;
+        goto do_rep;
+    }
+
 #endif
 }
 
diff --git a/pc/disdec.c b/pc/disd.c
similarity index 100%
rename from pc/disdec.c
rename to pc/disd.c
diff --git a/pc/dump.c b/pc/dump.c
index a4a181f..6dd89b5 100644
--- a/pc/dump.c
+++ b/pc/dump.c
@@ -3,25 +3,6 @@
 
 #include "arch.h"
 
-void dumpregs(ctx_t *ctx)
-{
-    int i;
-    reg_t *r;
-    
-    log("\nRegisters:\n");
-    log("rip=0x%016lX flg=0x%016lX", ctx->r[RIP].val, ctx->r[FLG].val);
-    
-    for (i = 0; i < K0; i++) {
-        if (i % 4 == 0)
-            log("\n");
-        
-        r = &ctx->r[i];
-        log("%s%s=0x%016lX ", r->name,
-            (strlen(r->name) == 2 ? "=" : ""), r->val);
-    }
-    log("\n");
-}
-
 void dumpmem(ctx_t *ctx, ulong start, ulong size)
 {
     uint i;
@@ -63,24 +44,27 @@ void d_log(ctx_t *ctx, char *fmt, ...)
     va_end(ap);
 }
 
-void dumpinstr(ctx_t *ctx, ulong rip, ushort c, acc_t *p1, acc_t *p2)
+void dumpinstr(ctx_t *ctx, ulong rip, uint rep,
+               ushort c, acc_t *p1, acc_t *p2)
 {
     acc_t *p = 0;
     instr_t *i = &ctx->i[c];
 
-    d_log(ctx, "0x%08lX: %s", rip, i->name);
+    d_log(ctx, "0x%08lX: %s%s", rip,
+        (rep ? "rep " : ""),
+        i->name);
     
     if (i->prm1 != NOPRM)
         p = p1;
 lp:
     if (p != 0) {
-        if (p->mem) d_log(ctx, " [");
+        if (p->mem) d_log(ctx, " %c:[", getmempref(p->mlen));
         else d_log(ctx, " ");
         
         if (p->type == A_REG)
             d_log(ctx, "%s", ctx->r[p->val].name);
         else
-            d_log(ctx, "0x%lX", p->val);
+            d_log(ctx, "%c:0x%lX", getmempref(p->ilen), p->val);
         
         if (p->mem) {
             if (p->off)
diff --git a/pc/except.c b/pc/except.c
index 4cae3bb..8619df8 100644
--- a/pc/except.c
+++ b/pc/except.c
@@ -20,6 +20,6 @@ void _except(ctx_t *ctx, int code, char *fmt, ...)
 
     if (ctx->mp)
         free(ctx->mp);
-    exit(code+1);
+    exit(code);
 }
 
diff --git a/pc/instrs.c b/pc/instrs.c
deleted file mode 100644
index 770478b..0000000
--- a/pc/instrs.c
+++ /dev/null
@@ -1,298 +0,0 @@
-// The OS/K Team licences this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-#include "instrs.h"
-#include "arch_i.h"
-
-#define _NEED_ARCH_I
-#include "arch_i.h"
-
-IMPL_START_0(nop)
-{
-}
-IMPL_END;
-
-//
-// Logical instructions
-//
-
-IMPL_START_2(and)
-{
-    v1 &= v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(or)
-{
-    v1 |= v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(xor)
-{
-    v1 ^= v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(shl)
-{
-    v1 <<= v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(shr)
-{
-    v1 >>= v2;
-}
-IMPL_OUT;
-
-IMPL_START_1(not)
-{
-    v1 = ~v1;
-}
-IMPL_OUT;
-
-//
-// Unsigned arithmetic instructions
-//
-
-IMPL_START_2(add)
-{
-    v1 += v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(sub)
-{
-    v1 -= v2;
-}
-IMPL_OUT;
-
-IMPL_START_1(mul)
-{
-    // Adapted from www.codeproject.com/Tips/618570/UInt-Multiplication-Squaring
-    ulong v2 = v1;
-    v1 = ctx->r[RAX].val;
-
-    ulong u1 = (v1 & 0xffffffff);
-    ulong u2 = (v2 & 0xffffffff);
-    ulong t = (u1 * u2);
-    ulong w3 = (t & 0xffffffff);
-    ulong k = (t >> 32);
-    
-    v1 >>= 32;
-    t = (v1 * u2) + k;
-    k = (t & 0xffffffff);
-    ulong w1 = (t >> 32);
-    
-    v2 >>= 32;
-    t = (u1 * v2) + k;
-    k = (t >> 32);
-    
-    ctx->r[RDX].val = (v1 * v2) + w1 + k;
-    ctx->r[RAX].val = (t << 32) + w3;
-}
-IMPL_END;
-
-IMPL_START_1(div)
-{
-    ctx->r[RDX].val = ctx->r[RAX].val % v1;
-    ctx->r[RAX].val = ctx->r[RAX].val / v1;
-}
-IMPL_END;
-
-IMPL_START_1(inc)
-{
-    v1++;
-}
-IMPL_OUT;
-
-IMPL_START_1(dec)
-{
-    v1--;
-}
-IMPL_OUT;
-
-//
-// Comparison instructions
-//
-
-IMPL_START_2(cmp)
-{
-    if (v1 == v2) {
-        ctx->r[FLG].val |= ZF;
-        ctx->r[FLG].val &= ~CF;
-    }
-    
-    else if (v1 < v2) {
-        ctx->r[FLG].val &= ~ZF;
-        ctx->r[FLG].val |= CF;
-    }
-
-    else {
-        ctx->r[FLG].val &= ~ZF;
-        ctx->r[FLG].val &= ~CF;
-    }
-}
-IMPL_END;
-
-IMPL_START_2(test)
-{
-    ulong v = v1 & v2;
-    
-    if (v == 0) ctx->r[FLG].val |= ZF;
-    else ctx->r[FLG].val &= ~ZF;
-}
-IMPL_END;
-
-//
-// Jump instructions
-//
-
-//
-// Movement instructions
-//
-
-IMPL_START_2(mov)
-{
-    v1 = v2;
-}
-IMPL_OUT;
-
-IMPL_START_2(xchg)
-{
-    ulong t = v1;
-    v1 = v2;
-    v2 = t;
-}
-IMPL_OUT;
-
-IMPL_START_1(lea)
-{
-    assert(p2->mem);
-    
-    v1 = (p2->type == A_REG ? ctx->r[p2->val].val : p2->val) + p2->off;
-}
-IMPL_OUT;
-
-//
-// Stack manipulation instructions
-//
-
-IMPL_START_1(push)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val > ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RSP above RBP");
-    }
-
-    writemem64(ctx, v1, ctx->r[RSP].val);
-    ctx->r[RSP].val -= 8;
-}
-IMPL_END;
-
-IMPL_START_1(pop)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val >= ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RBP above RSP");
-    }
-
-    ctx->r[RSP].val += 8;
-    v1 = readmem64(ctx, ctx->r[RSP].val);
-}
-IMPL_OUT;
-
-IMPL_START_1(call)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val > ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RSP above RBP");
-    }
-
-    writemem64(ctx, ctx->r[RIP].val, ctx->r[RSP].val);
-    ctx->r[RSP].val -= 8;
-    ctx->r[RIP].val = v1;
-}
-IMPL_END;
-
-IMPL_START_0(ret)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val >= ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RBP above RSP");
-    }
-
-    ctx->r[RSP].val += 8;
-    ctx->r[RIP].val = readmem64(ctx, ctx->r[RSP].val);
-}
-IMPL_END;
-
-IMPL_START_0(pushf)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val > ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RSP above RBP");
-    }
-
-    writemem64(ctx, ctx->r[FLG].val, ctx->r[RSP].val);
-    ctx->r[RSP].val -= 8;
-}
-IMPL_END;
-
-IMPL_START_0(popf)
-{
-    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {
-       _except(ctx, E_STK, "Misaligned stack REGS");
-    }
-
-    if (ctx->r[RSP].val >= ctx->r[RBP].val) {
-        _except(ctx, E_STK, "RBP above RSP");
-    }
-    
-    CHK_SUPERV(); // XXX
-
-    ctx->r[RSP].val += 8;
-    ctx->r[FLG].val = readmem64(ctx, ctx->r[RSP].val);
-}
-IMPL_END;
-
-//
-// Supervisor only instructions
-//
-
-IMPL_START_0(cli)
-{
-    CHK_SUPERV();
-    ctx->r[FLG].val &= ~IF;
-}
-IMPL_END;
-
-IMPL_START_0(sti)
-{
-    CHK_SUPERV();
-    ctx->r[FLG].val |= IF;
-}
-IMPL_END;
-
-IMPL_START_0(stop)
-{
-    _except(ctx, E_SHT, "STOP INSTR");
-}
-IMPL_END;
-
diff --git a/pc/INSTRS b/pc/instrs/INSTRS
similarity index 92%
rename from pc/INSTRS
rename to pc/instrs/INSTRS
index 896e123..bc5a4f7 100644
--- a/pc/INSTRS
+++ b/pc/instrs/INSTRS
@@ -157,14 +157,19 @@ xchg m m
 lea r m
 lea m m
 
+# get code segment
+gcs r m
+
 #
 # Stack manipulation instructions
 #
 
 push i
 push r
+push m
 
 pop r
+pop m
 
 call r
 call i
@@ -172,6 +177,9 @@ call m
 
 ret
 
+enter
+leave
+
 pushf
 
 #
@@ -183,3 +191,8 @@ popf
 cli
 sti
 
+# Prints a character on the screen
+prn r
+prn i
+prn m
+
diff --git a/pc/instrs.py b/pc/instrs/arch_i.py
similarity index 96%
rename from pc/instrs.py
rename to pc/instrs/arch_i.py
index f1b4940..f51911f 100644
--- a/pc/instrs.py
+++ b/pc/instrs/arch_i.py
@@ -9,7 +9,7 @@ ls = open("instrs.lst", "w")
 
 count = 0
 
-hd.write("// Auto-generated by instrs.py from INSTRS\n\n");
+hd.write("// Auto-generated by arch_i.py from INSTRS\n\n");
 
 hd.write("#ifdef _NEED_ARCH_I\n")
 hd.write("instr_t arch_i[] =\n{\n\n")
diff --git a/pc/instrs/arith.c b/pc/instrs/arith.c
new file mode 100644
index 0000000..638c864
--- /dev/null
+++ b/pc/instrs/arith.c
@@ -0,0 +1,67 @@
+// The OS/K Team licences this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "instrs.h"
+#include "arch_i.h"
+
+//
+// Unsigned arithmetic instructions
+//
+
+IMPL_START_2(add)
+{
+    v1 += v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(sub)
+{
+    v1 -= v2;
+}
+IMPL_OUT;
+
+IMPL_START_1(mul)
+{
+    // Adapted from www.codeproject.com/Tips/618570/UInt-Multiplication-Squaring
+    ulong v2 = v1;
+    v1 = ctx->r[RAX].val;
+
+    ulong u1 = (v1 & 0xffffffff);
+    ulong u2 = (v2 & 0xffffffff);
+    ulong t = (u1 * u2);
+    ulong w3 = (t & 0xffffffff);
+    ulong k = (t >> 32);
+    
+    v1 >>= 32;
+    t = (v1 * u2) + k;
+    k = (t & 0xffffffff);
+    ulong w1 = (t >> 32);
+    
+    v2 >>= 32;
+    t = (u1 * v2) + k;
+    k = (t >> 32);
+    
+    ctx->r[RDX].val = (v1 * v2) + w1 + k;
+    ctx->r[RAX].val = (t << 32) + w3;
+}
+IMPL_END;
+
+IMPL_START_1(div)
+{
+    ctx->r[RDX].val = ctx->r[RAX].val % v1;
+    ctx->r[RAX].val = ctx->r[RAX].val / v1;
+}
+IMPL_END;
+
+IMPL_START_1(inc)
+{
+    v1++;
+}
+IMPL_OUT;
+
+IMPL_START_1(dec)
+{
+    v1--;
+}
+IMPL_OUT;
+
diff --git a/pc/instrs/instrs.c b/pc/instrs/instrs.c
new file mode 100644
index 0000000..b98c014
--- /dev/null
+++ b/pc/instrs/instrs.c
@@ -0,0 +1,70 @@
+// The OS/K Team licences this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "instrs.h"
+#include "arch_i.h"
+
+#define _NEED_ARCH_I
+#include "arch_i.h"
+
+IMPL_START_0(nop)
+{
+}
+IMPL_END;
+
+//
+// Movement instructions
+//
+
+IMPL_START_2(mov)
+{
+    v1 = v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(xchg)
+{
+    ulong t = v1;
+    v1 = v2;
+    v2 = t;
+}
+IMPL_OUT;
+
+IMPL_START_1(lea)
+{
+    assert(p2->mem);
+    
+    v1 = (p2->type == A_REG ? ctx->r[p2->val].val : p2->val) + p2->off;
+}
+IMPL_OUT;
+
+IMPL_START_1(gcs)
+{
+    v1 = ctx->r[CR1].val;
+}
+IMPL_OUT;
+
+//
+// Misc. instructions
+//
+
+IMPL_START_1(prn)
+{
+    if (p1->mlen > 1) {
+        log("prn warning: large access size\n");
+    }
+
+    if (!(v1 >= ' ' && v1 < 128) && v1 != '\t') {
+        if (v1 == '\n') {
+            log("prn on newline character\n");
+        }
+        else
+            log("prn on invalid character: %ld\n", v1);
+    }
+
+    else {
+        log("prn instruction with character: '%c'\n", (char)v1);
+    }
+}
+IMPL_END;
+
diff --git a/pc/instrs.h b/pc/instrs/instrs.h
similarity index 64%
rename from pc/instrs.h
rename to pc/instrs/instrs.h
index cdb846c..ef42c07 100644
--- a/pc/instrs.h
+++ b/pc/instrs/instrs.h
@@ -1,7 +1,7 @@
 // The OS/K Team licences this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#include "arch.h"
+#include "../arch.h"
 
 #define IMPL_START_0(name)                                                  \
 void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
@@ -11,27 +11,27 @@ void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
 void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
 {                                                                           \
     ulong v1 = (p1->type == A_REG ? ctx->r[p1->val].val : p1->val);         \
-    if (p1->mem) v1 = readmem(ctx, v1 + p1->off, p1->len);                  \
+    if (p1->mem) v1 = readmem(ctx, v1 + p1->off, p1->mlen);                 \
 
 #define IMPL_START_2(name)                                                  \
 void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
 {                                                                           \
     ulong v1 = (p1->type == A_REG ? ctx->r[p1->val].val : p1->val);         \
     ulong v2 = (p2->type == A_REG ? ctx->r[p2->val].val : p2->val);         \
-    if (p1->mem) v1 = readmem(ctx, v1 + p1->off, p1->len);                  \
-    if (p2->mem) v2 = readmem(ctx, v2 + p2->off, p2->len);                  \
+    if (p1->mem) v1 = readmem(ctx, v1 + p1->off, p1->mlen);                 \
+    if (p2->mem) v2 = readmem(ctx, v2 + p2->off, p2->mlen);                 \
 
 #define IMPL_START_3(name)                                                  \
 void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
 {                                                                           \
     ulong v2 = (p2->type == A_REG ? ctx->r[p2->val].val : p2->val);         \
-    if (p2->mem) v2 = readmem(ctx, v2 + p2->off, p2->len);                  \
+    if (p2->mem) v2 = readmem(ctx, v2 + p2->off, p2->mlen);                 \
 
 #define IMPL_OUT                                                            \
     assert(p1->type == A_REG || p1->mem);                                   \
     if (p1->mem) {                                                          \
         ulong addr = p1->type == A_REG ? ctx->r[p1->val].val : p1->val;     \
-        writemem(ctx, v1, addr, p1->len);                                   \
+        writemem(ctx, v1, addr, p1->mlen);                                  \
     }                                                                       \
     else ctx->r[p1->val].val = v1;                                          \
 }                                                                           \
@@ -46,3 +46,25 @@ void i_##name(ctx_t *ctx, acc_t *p1, acc_t *p2)                             \
         }                                                                   \
     } while (0)
 
+#define CHK_STACK(op)                                                       \
+    if (ctx->r[RSP].val % 8 > 0 || ctx->r[RBP].val % 8 > 0) {               \
+       _except(ctx, E_STK, "Misaligned stack REGS");                        \
+    }                                                                       \
+    if (ctx->r[RBP].val op ctx->r[RSP].val) {                               \
+        _except(ctx, E_STK, "RSP above RBP");                               \
+    }
+
+#define PUSH(v)                                                             \
+    writemem64(ctx, v, ctx->r[RSP].val);                                    \
+    ctx->r[RSP].val -= 8;                                                   \
+
+#define POP(v)                                                              \
+    ctx->r[RSP].val += 8;                                                   \
+    v = readmem64(ctx, ctx->r[RSP].val);
+
+#define JUMP(v)                                                             \
+    ctx->r[RIP].val = v + ctx->r[CR1].val
+
+
+
+
diff --git a/pc/jumps.c b/pc/instrs/jumps.c
similarity index 76%
rename from pc/jumps.c
rename to pc/instrs/jumps.c
index 607aa4f..1ca7b63 100644
--- a/pc/jumps.c
+++ b/pc/instrs/jumps.c
@@ -4,6 +4,10 @@
 #include "instrs.h"
 #include "arch_i.h"
 
+//
+// Jump instructions
+//
+
 IMPL_START_1(jmp)
 {
     ctx->r[RIP].val = v1;
@@ -13,62 +17,62 @@ IMPL_END;
 IMPL_START_1(jz)
 {
     if (ctx->r[FLG].val & ZF)
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jnz)
 {
     if (!(ctx->r[FLG].val & ZF))
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(je)
 {
     if (ctx->r[FLG].val & ZF)
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jne)
 {
     if (!(ctx->r[FLG].val & ZF))
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(ja)
 {
     if (!(ctx->r[FLG].val & ZF) && !(ctx->r[FLG].val & CF))
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jae)
 {
     if (!(ctx->r[FLG].val & CF))
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jb)
 {
     if (!(ctx->r[FLG].val & ZF) && ctx->r[FLG].val & CF)
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jbe)
 {
     if (ctx->r[FLG].val & CF)
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
 
 IMPL_START_1(jcxz)
 {
     if (!ctx->r[RCX].val)
-        ctx->r[RIP].val = v1;
+        JUMP(v1);
 }
 IMPL_END;
diff --git a/pc/instrs/logic.c b/pc/instrs/logic.c
new file mode 100644
index 0000000..721fa68
--- /dev/null
+++ b/pc/instrs/logic.c
@@ -0,0 +1,78 @@
+// The OS/K Team licences this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "instrs.h"
+#include "arch_i.h"
+
+//
+// Comparison instructions
+//
+
+IMPL_START_2(test)
+{
+    ulong v = v1 & v2;
+    
+    if (v == 0) ctx->r[FLG].val |= ZF;
+    else ctx->r[FLG].val &= ~ZF;
+}
+IMPL_END;
+
+IMPL_START_2(cmp)
+{
+    if (v1 == v2) {
+        ctx->r[FLG].val |= ZF;
+        ctx->r[FLG].val &= ~CF;
+    }
+    
+    else if (v1 < v2) {
+        ctx->r[FLG].val &= ~ZF;
+        ctx->r[FLG].val |= CF;
+    }
+
+    else {
+        ctx->r[FLG].val &= ~ZF;
+        ctx->r[FLG].val &= ~CF;
+    }
+}
+IMPL_END;
+
+//
+// Logical instructions
+//
+
+IMPL_START_2(and)
+{
+    v1 &= v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(or)
+{
+    v1 |= v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(xor)
+{
+    v1 ^= v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(shl)
+{
+    v1 <<= v2;
+}
+IMPL_OUT;
+
+IMPL_START_2(shr)
+{
+    v1 >>= v2;
+}
+IMPL_OUT;
+
+IMPL_START_1(not)
+{
+    v1 = ~v1;
+}
+IMPL_OUT;
+
diff --git a/pc/instrs/stack.c b/pc/instrs/stack.c
new file mode 100644
index 0000000..ee29bf2
--- /dev/null
+++ b/pc/instrs/stack.c
@@ -0,0 +1,75 @@
+// The OS/K Team licences this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "instrs.h"
+#include "arch_i.h"
+
+//
+// Stack manipulation instructions
+//
+
+IMPL_START_1(push)
+{
+    CHK_STACK(<);
+    PUSH(v1);
+}
+IMPL_END;
+
+IMPL_START_1(pop)
+{
+    CHK_STACK(<=);
+    POP(v1);
+}
+IMPL_OUT;
+
+IMPL_START_1(call)
+{
+    CHK_STACK(<);
+    PUSH(ctx->r[RIP].val);
+    JUMP(v1);
+}
+IMPL_END;
+
+IMPL_START_0(ret)
+{
+    CHK_STACK(<=);
+    POP(ctx->r[RIP].val);
+}
+IMPL_END;
+
+IMPL_START_0(enter)
+{
+    CHK_STACK(<);
+    PUSH(ctx->r[RBP].val);
+    ctx->r[RBP].val = ctx->r[RSP].val;
+}
+IMPL_END;
+
+IMPL_START_0(leave)
+{
+    // Do NOT check stack here!
+    POP(ctx->r[RBP].val);
+}
+IMPL_END;
+
+IMPL_START_0(pushf)
+{
+    CHK_STACK(<);
+
+    writemem64(ctx, ctx->r[FLG].val, ctx->r[RSP].val);
+    ctx->r[RSP].val -= 8;
+}
+IMPL_END;
+
+IMPL_START_0(popf)
+{
+    CHK_STACK(<=);
+    
+    CHK_SUPERV(); // XXX
+
+    ctx->r[RSP].val += 8;
+    ctx->r[FLG].val = readmem64(ctx, ctx->r[RSP].val);
+}
+IMPL_END;
+
+
diff --git a/pc/instrs/super.c b/pc/instrs/super.c
new file mode 100644
index 0000000..a3812f2
--- /dev/null
+++ b/pc/instrs/super.c
@@ -0,0 +1,30 @@
+// The OS/K Team licences this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "instrs.h"
+#include "arch_i.h"
+
+//
+// Supervisor only instructions
+//
+
+IMPL_START_0(cli)
+{
+    CHK_SUPERV();
+    ctx->r[FLG].val &= ~IF;
+}
+IMPL_END;
+
+IMPL_START_0(sti)
+{
+    CHK_SUPERV();
+    ctx->r[FLG].val |= IF;
+}
+IMPL_END;
+
+IMPL_START_0(stop)
+{
+    _except(ctx, E_SHT, "STOP INSTR");
+}
+IMPL_END;
+
diff --git a/pc/main.c b/pc/main.c
index ecef88f..1b37a33 100644
--- a/pc/main.c
+++ b/pc/main.c
@@ -18,7 +18,7 @@ ushort bget(ctx_t *ctx)
         _except(ctx, E_ACC, "Executing out of memory: 0x%016lX",
             ctx->r[RIP].val);
     }
-    
+
     ushort c = ctx->mp[addr2real(ctx->r[RIP].val)];
     
     ctx->r[RIP].val += 2;
@@ -40,9 +40,6 @@ ushort dget(ctx_t *ctx)
     return fwprog[i++];
 }
 
-extern reg_t arch_r[NREGS];
-extern instr_t arch_i[NINSTRS];
-
 int main(int argc, char **argv)
 {
     ctx_t main_ctx;
diff --git a/pc/mem.c b/pc/mem.c
index 30c7b8d..c5a6d62 100644
--- a/pc/mem.c
+++ b/pc/mem.c
@@ -16,26 +16,28 @@ ulong readmem(ctx_t *ctx, ulong addr, uint len)
 
 ulong readmem8(ctx_t *ctx, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
     
-    if (addr % 2) return (ulong)ctx->mp[real] & 0xFF;
+    if (addr % 2 == 0) return (ulong)ctx->mp[real] & 0xFF;
     else return ((ulong)ctx->mp[real] & 0xFF00) >> 8;
 }
 
 ulong readmem16(ctx_t *ctx, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(ushort) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     return (ulong)ctx->mp[real];
@@ -43,44 +45,47 @@ ulong readmem16(ctx_t *ctx, ulong addr)
 
 ulong readmem32(ctx_t *ctx, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(uint) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
-    ulong val = (ulong)ctx->mp[real++];
-    val = (val << 16) | (ulong)ctx->mp[real];
+    ulong val = ctx->mp[real++];
+    val = val | ((ulong)ctx->mp[real] << 16);
     
     return val;
 }
 
 ulong readmem64(ctx_t *ctx, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(ulong) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     ulong val = (ulong)ctx->mp[real++];
-    val = (val << 16) | (ulong)ctx->mp[real++];
-    val = (val << 16) | (ulong)ctx->mp[real++];
-    val = (val << 16) | (ulong)ctx->mp[real];
+    val = val | ((ulong)ctx->mp[real++] << 16);
+    val = val | ((ulong)ctx->mp[real++] << 32);
+    val = val | ((ulong)ctx->mp[real] << 48);
     
     return val;
 }
 
 void writemem(ctx_t *ctx, ulong val, ulong addr, uint len)
 {
+    addr += ctx->r[CR2].val;
     switch (len) {
         case 1: writemem8(ctx, val, addr); break;
         case 2: writemem16(ctx, val, addr); break;
@@ -92,10 +97,11 @@ void writemem(ctx_t *ctx, ulong val, ulong addr, uint len)
 
 void writemem8(ctx_t *ctx, ulong val, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     ushort v = ctx->mp[real];
@@ -111,14 +117,15 @@ void writemem8(ctx_t *ctx, ulong val, ulong addr)
 
 void writemem16(ctx_t *ctx, ulong val, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(ushort) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     ctx->mp[real] = val & 0xFFFF;
@@ -126,34 +133,37 @@ void writemem16(ctx_t *ctx, ulong val, ulong addr)
 
 void writemem32(ctx_t *ctx, ulong val, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(uint) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
-    ctx->mp[real++] = (val >> 16) & 0xFFFF;
-    ctx->mp[real] = val & 0xFFFF;
+    ctx->mp[real++] = val & 0xFFFF;
+    ctx->mp[real] = (val >> 16) & 0xFFFF;
 }
 
 void writemem64(ctx_t *ctx, ulong val, ulong addr)
 {
+    addr += ctx->r[CR2].val;
     ulong real = addr2real(addr);
 
     if (addr % alignof(ulong) > 0) {
-        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ALI, "Non-aligned memory access: 0x%012lX (0x%012lX)", addr, real);
     }
 
     if (addr < MEMOFF || real >= MEMSIZE) {
-        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX(0x%012lX)", addr, real);
+        _except(ctx, E_ACC, "Invalid MEM access: 0x%012lX (0x%012lX)", addr, real);
     }
 
-    ctx->mp[real++] = val >> 48;
-    ctx->mp[real++] = (val >> 32) & 0xFFFF;
+    ctx->mp[real++] = val;
     ctx->mp[real++] = (val >> 16) & 0xFFFF;
-    ctx->mp[real] = val & 0xFFFF;
+    ctx->mp[real++] = (val >> 32) & 0xFFFF;
+    ctx->mp[real] = (val >> 48) & 0xFFFF;
 }
+
diff --git a/pc/regs.c b/pc/regs.c
index 35c2cc0..469df6e 100644
--- a/pc/regs.c
+++ b/pc/regs.c
@@ -6,39 +6,85 @@
 reg_t arch_r[NREGS] =
 {
     { "inv", "Invalid register", 0, RES },
-    { "rax", "Accumulator 0", 0, GPR },
-    { "rbx", "Accumulator 1", 0, GPR },
-    { "rcx", "Accumulator 2", 0, GPR },
-    { "rdx", "Accumulator 3", 0, GPR },
-    { "rdi", "Accumulator 4", 0, GPR },
-    { "rsi", "Accumulator 5", 0, GPR },
-    { "rbp", "Stack base",    0, GPR },
-    { "rsp", "Stack pointer", 0, GPR },
-    { "r8", "Accumulator 8", 0, GPR },
-    { "r9", "Accumulator 9", 0, GPR },
-    { "r10", "Accumulator 10", 0, GPR },
-    { "r11", "Accumulator 11", 0, GPR },
-    { "r12", "Accumulator 12", 0, GPR },
-    { "r13", "Accumulator 13", 0, GPR },
-    { "r14", "Accumulator 14", 0, GPR },
-    { "r15", "Accumulator 15", 0, GPR },
-    { "k0", "Supervisor accumulator 0", 0, SYS },
-    { "k1", "Supervisor accumulator 1", 0, SYS },
-    { "k2", "Supervisor accumulator 2", 0, SYS },
-    { "k3", "Supervisor accumulator 3", 0, SYS },
-    { "k4", "Supervisor accumulator 4", 0, SYS },
-    { "k5", "Supervisor accumulator 5", 0, SYS },
-    { "k6", "Supervisor accumulator 6", 0, SYS },
-    { "k7", "Supervisor accumulator 7", 0, SYS },
-    { "cr0", "Control register 0", 0, CTL },
-    { "cr1", "Control register 1", 0, CTL },
-    { "cr2", "Control register 2", 0, CTL },
-    { "cr3", "Control register 3", 0, CTL },
-    { "cr4", "Control register 4", 0, CTL },
-    { "cr5", "Control register 5", 0, CTL },
-    { "cr6", "Control register 6", 0, CTL },
-    { "cr7", "Control register 7", 0, CTL },
-    { "rip", "Instruction pointer", 0, RES },
-    { "flg", "Flags register",      0, RES },
+
+    { "rip", "Instruction pointer", "Special; Volatile", 0, RES },
+    { "flg", "Flags register", "Special; Volatile", 0, RES },
+
+    { "rbp", "Stack base",    "Special; Non-volatile", 0, GPR },
+    { "rsp", "Stack pointer", "Special; Non-volatile", 0, GPR },
+
+    { "rax", "Accumulator 0", "Volatile", 0, GPR },
+    { "rbx", "Accumulator 1", "Volatile", 0, GPR },
+    { "rcx", "Accumulator 2", "Volatile", 0, GPR },
+    { "rdx", "Accumulator 3", "Volatile", 0, GPR },
+    { "rsx", "Accumulator 4", "Volatile", 0, GPR },
+    { "rbi", "Accumulator 5", "Volatile", 0, GPR },
+    { "rdi", "Accumulator 6", "Volatile", 0, GPR },
+    { "rsi", "Accumulator 7", "Volatile", 0, GPR },
+
+    { "nx0", "Accumulator 8", "Non-volatile", 0, GPR },
+    { "nx1", "Accumulator 9", "Non-volatile", 0, GPR },
+    { "nx2", "Accumulator 10", "Non-volatile", 0, GPR },
+    { "nx3", "Accumulator 11", "Non-volatile", 0, GPR },
+    { "nx4", "Accumulator 12", "Non-volatile", 0, GPR },
+    { "nx5", "Accumulator 13", "Non-volatile", 0, GPR },
+    { "nx6", "Accumulator 14", "Non-volatile", 0, GPR },
+    { "nx7", "Accumulator 15", "Non-volatile", 0, GPR },
+    
+    { "ax0", "Argument 0", "Volatile", 0, GPR },
+    { "ax1", "Argument 1", "Volatile", 0, GPR },
+    { "ax2", "Argument 2", "Volatile", 0, GPR },
+    { "ax3", "Argument 3", "Volatile", 0, GPR },
+    { "ax4", "Argument 4", "Volatile", 0, GPR },
+    { "ax5", "Argument 5", "Volatile", 0, GPR },
+    { "ax6", "Argument 6", "Volatile", 0, GPR },
+    { "ax7", "Argument 7", "Volatile", 0, GPR },
+
+    // cr0: various flags
+    { "cr0", "Control register 0", "Control", 0, CTL },
+    
+    // cr1: code offset
+    { "cr1", "Control register 1", "Control", 0x100000, CTL },
+    
+    // cr2: data offset
+    { "cr2", "Control register 2", "Control", 0x100000, CTL },
+
+    // unused
+    { "cr3", "Control register 3", "Control", 0, CTL },
+    { "cr4", "Control register 4", "Control", 0, CTL },
+    { "cr5", "Control register 5", "Control", 0, CTL },
+    { "cr6", "Control register 6", "Control", 0, CTL },
+    { "cr7", "Control register 7", "Control", 0, CTL },
+
+    { "sa0", "Supervisor acc. 0", "System; Non-volatile", 0, SYS },
+    { "sa1", "Supervisor acc. 1", "System; Non-volatile", 0, SYS },
+    { "sa2", "Supervisor acc. 2", "System; Non-volatile", 0, SYS },
+    { "sa3", "Supervisor acc. 3", "System; Non-volatile", 0, SYS },
+    { "sa4", "Supervisor acc. 4", "System; Non-volatile", 0, SYS },
+    { "sa5", "Supervisor acc. 5", "System; Non-volatile", 0, SYS },
+    { "sa6", "Supervisor acc. 6", "System; Non-volatile", 0, SYS },
+    { "sa7", "Supervisor acc. 7", "System; Non-volatile", 0, SYS },
 };
 
+void dumpregs(ctx_t *ctx)
+{
+    int i;
+    reg_t *r;
+    
+    //assert(ctx->r[INV].val == 0);
+    
+    log("\nRegisters:\n");
+    log("rip=0x%-16lX flg=0x%-16lX ", ctx->r[RIP].val, ctx->r[FLG].val);
+    log("rbp=0x%-16lX rsp=0x%-16lX", ctx->r[RBP].val, ctx->r[RSP].val);
+    
+    for (i = RAX; i < CR4; i++) {
+        if ((i-1) % 4 == 0)
+            log("\n");
+        
+        r = &ctx->r[i];
+        log("%s%s=0x%-16lX ", r->name,
+            (strlen(r->name) == 2 ? "=" : ""), r->val);
+    }
+    log("\n");
+}
+
diff --git a/pc/regs.h b/pc/regs.h
new file mode 100644
index 0000000..7afa634
--- /dev/null
+++ b/pc/regs.h
@@ -0,0 +1,95 @@
+// The OS/K Team licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+enum
+{
+    INV,
+
+    RIP,
+    FLG,
+
+    RBP,
+    RSP,
+
+    RAX,
+    RBX,
+    RCX,
+    RDX,
+    RSX,
+    RBI,
+    RDI,
+    RSI,
+
+    NX0,
+    NX1,
+    NX2,
+    NX3,
+    NX4,
+    NX5,
+    NX6,
+    NX7,
+    
+    AX0,
+    AX1,
+    AX2,
+    AX3,
+    AX4,
+    AX5,
+    AX6,
+    AX7,
+    
+    CR0,
+    CR1,
+    CR2,
+    CR3,
+    CR4,
+    CR5,
+    CR6,
+    CR7,
+    
+    SA0,
+    SA1,
+    SA2,
+    SA3,
+    SA4,
+    SA5,
+    SA6,
+    SA7,
+
+    NREGS
+};
+
+enum 
+{
+    GPR = 1 << 0,   // General
+    CTL = 1 << 1,   // Control
+    SEG = 1 << 2,   // Segment
+    RES = 1 << 8,   // Reserved for insternal use
+    SYS = 1 << 9,   // Reserved for supervisor mode
+};
+
+// FLG register
+enum
+{
+    CF = 1 << 0,        // Carry flag
+    PF = 1 << 1,        // Parity flag
+    AC = 1 << 2,        // Auxiliary flag
+    ZF = 1 << 3,        // Zero flag
+    OV = 1 << 4,        // Overflow flag
+    DF = 1 << 5,        // Direction flag
+    SF = 1 << 6,        // Sign flag
+    
+    UF = 1 << 16,       // User-mode flag
+    IF = 1 << 17,       // Interrupts enable flag
+};
+
+struct reg_t
+{
+    char   *name;
+    char   *desc;
+    char   *conv;
+    ulong   val;
+    ulong   flags;
+};
+
+