diff --git a/as/k-as.py b/as/k-as.py
index 642da44..92b32e2 100755
--- a/as/k-as.py
+++ b/as/k-as.py
@@ -283,7 +283,9 @@ def parse_instr(line):
             word = word[1:-1]
 
             if pref == None:
-                pref = "%q"
+                print("Missing access length modifier: {}".format(line))
+                leave()
+                sys.exit(1)
 
             instr_name += "_m"
             instr_args += "{}".format(pref)
diff --git a/as/testfile.asm b/as/testfile.asm
index 187f3af..9f5de3b 100644
--- a/as/testfile.asm
+++ b/as/testfile.asm
@@ -3,33 +3,63 @@
 
 hw = 'Hello World'
 
+;
+; Entry point
+;
 main:
     ; This comment is successfully ignored
     mov rbp, 0x200000
     mov rsp, rbp
     
     mov ax0, hw
-    mov ax1, hw_len
     call print
+    
+    mov ax0, hw
+    mov ax1, hw_len
+    call print_n
 
     stop
 
+;
+; Max amount of characters that print() will print
+;
+v_print_max := 0xFF
+
+;
+; void print(char *)
+;
+; Print a string
+;
 print:
     enter
+    mov rcx, v_print_max
 
+.p1:
+    test b[ax0], b[ax0]
+    jz .p2
+    prn b[ax0]
+    inc ax0
+    loop .p1
+
+.p2:
+    leave
+    ret
+
+
+;
+; void print_n(char *, int)
+;
+; Print exactly ax1 characters
+;
+print_n:
+    enter
     mov rcx, ax1
-    rep call .pch1
+
+.pn1:
+    prn b[ax0]
+    inc ax0
+    loop .pn1
 
     leave
     ret
 
-.pch1:
-    test b[ax0], b[ax0]
-    jnz .pch2
-    ret
-
-.pch2:
-    prn b[ax0]
-    inc ax0
-    ret
-
diff --git a/pc/decd.c b/pc/decd.c
index c7e1061..5641c8c 100644
--- a/pc/decd.c
+++ b/pc/decd.c
@@ -117,14 +117,17 @@ void disasm(ctx_t *ctx)
         }
     }
 
+#ifdef _NEED_DISASM
     dumpinstr(ctx, rip, rep, c, &p1, &p2);
+#else
     
-#ifndef _NEED_DISASM
-
 do_rep:
     i->func(ctx, &p1, &p2);
 
+    dumpinstr(ctx, rip, rep, c, &p1, &p2);
+
     if (rep && ctx->r[RCX].val > 0) {
+        log("rcx::%lu\n", ctx->r[RCX].val);
         ctx->r[RCX].val--;
         goto do_rep;
     }
diff --git a/pc/instrs/INSTRS b/pc/instrs/INSTRS
index bc5a4f7..abe9a4b 100644
--- a/pc/instrs/INSTRS
+++ b/pc/instrs/INSTRS
@@ -115,6 +115,9 @@ test m m
 jmp r
 jmp i
 
+loop r
+loop i
+
 jz r
 jz i
 jnz r
diff --git a/pc/instrs/jumps.c b/pc/instrs/jumps.c
index 1ca7b63..049c3ea 100644
--- a/pc/instrs/jumps.c
+++ b/pc/instrs/jumps.c
@@ -10,7 +10,16 @@
 
 IMPL_START_1(jmp)
 {
-    ctx->r[RIP].val = v1;
+    JUMP(v1);
+}
+IMPL_END;
+
+IMPL_START_1(loop)
+{
+    if (ctx->r[RCX].val > 0) {
+        ctx->r[RCX].val--;
+        JUMP(v1);
+    }
 }
 IMPL_END;