diff --git a/.gitignore b/.gitignore
index 2211b64..04515c2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,7 @@ arch_i.h
 *.dis
 instrs.lst
 *.out*
+stdout.txt
+stderr.txt
+stdin.txt
 
diff --git a/Makefile b/Makefile
index eaf5f6f..bf0317b 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,7 @@ asm: os/dos.k
 	@cd os && ../as/k-as.py dos.k 0x100000 a.out
 
 test: kas asm
-	@pc/k.exe os/a.out
+	@pc/k.exe os/a.out > os/stdout.txt
 
 disasm: kas asm
 	@pc/k.exe os/a.out -d
diff --git a/as/k-as.py b/as/k-as.py
index 1e34dad..01758ce 100755
--- a/as/k-as.py
+++ b/as/k-as.py
@@ -134,11 +134,31 @@ def parse_preproc(line):
             s = s[1:-1]
 
             plabels_data[tok[0]] = pdata
-            pdefs[tok[0] + "_len"] = str(len(s))
+
+            real_len = 0
+            escaping = False
 
             for c in s:
+                # escape sequences
+                if c == '\\':
+                    escaping = True
+                    continue
+
+                if escaping:
+                    escaping = False
+                    
+                    if c == 'n':
+                        c = '\n'
+                    elif c == 't':
+                        c = '\t'
+                    else:
+                        print("Unrecognized escape sequence: {}".format(line))
+                        leave()
+                        sys.exit(1)
+
                 written = b_data.write(ord(c).to_bytes(1, byteorder='little', signed=False))
                 assert(written == 1)
+                real_len += 1
                 pdata += 1
                 
             # align
@@ -146,7 +166,9 @@ def parse_preproc(line):
                 written = b_data.write(int(0).to_bytes(1, byteorder='little', signed=False))
                 assert(written == 1)
                 pdata += 1
-        
+
+            pdefs[tok[0] + "_len"] = str(real_len)
+
         else:
             print("Invalid format: {}".format(line))
             leave()
diff --git a/os/dos.k b/os/dos.k
index fe57439..8be9229 100644
--- a/os/dos.k
+++ b/os/dos.k
@@ -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.
 
-hw = "Hello World"
+hw = "Hello World\n:)"
 
 ;
 ; Entry point
diff --git a/pc/Makefile b/pc/Makefile
index e59f9f6..58e6a39 100644
--- a/pc/Makefile
+++ b/pc/Makefile
@@ -5,12 +5,14 @@ all: k.exe
 
 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
+      instrs/stack.c instrs/super.c instrs/arith.c log.c
 
 obj = $(patsubst %.c,%.o,$(src))
 
+CFLAGS=-O2 -g -Wall -fno-builtin-log
+
 %.o: %.c i_arch.h *.h $(src)
-	@gcc -O2 -g -Wall -c $< -o $@
+	@gcc $(CFLAGS) -c $< -o $@
 
 i_arch.h: instrs/INSTRS instrs/arch_i.py
 	@cd instrs && python3 arch_i.py
diff --git a/pc/arch.h b/pc/arch.h
index a2f3c44..1b93fba 100644
--- a/pc/arch.h
+++ b/pc/arch.h
@@ -8,9 +8,6 @@
 #include <assert.h>
 #include <stdarg.h>
 
-#define log printf
-#define vlog vprintf
-
 #define packed __attribute__ ((__packed__))
 #define static_assert _Static_assert
 #define alignof _Alignof
@@ -27,6 +24,9 @@ typedef struct instr_t      instr_t;
 typedef struct acc_t        acc_t;
 typedef struct arch_t       arch_t;
 
+void log(const char *, ...);
+void vlog(const char *, va_list);
+
 // A_REG is implicit
 // A_MEM denotes a memory access
 // A_OFF is A_MEM but a 16-bit offset is expected immediatly next
diff --git a/pc/instrs/instrs.c b/pc/instrs/instrs.c
index 61bd583..bbb3ecd 100644
--- a/pc/instrs/instrs.c
+++ b/pc/instrs/instrs.c
@@ -56,16 +56,12 @@ IMPL_START_1(prn)
         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);
+    if (!(v1 >= ' ' && v1 < 128) && v1 != '\t' && v1 != '\n') {
+        log("prn on invalid character: %ld\n", v1);
     }
 
     else {
-        log("prn instruction with character: '%c'\n", (char)v1);
+        putchar((int)v1);
     }
 }
 IMPL_END;
diff --git a/pc/log.c b/pc/log.c
new file mode 100644
index 0000000..1ab4a6e
--- /dev/null
+++ b/pc/log.c
@@ -0,0 +1,19 @@
+// 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 "arch.h"
+
+void log(const char *fmt, ...)
+{
+    va_list ap;
+    
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+}
+
+void vlog(const char *fmt, va_list ap)
+{
+    vfprintf(stderr, fmt, ap);
+}
+