diff --git a/src/ikarus.boot b/src/ikarus.boot
index 440d79f..160e83b 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.fasl.write.ss b/src/ikarus.fasl.write.ss
index 64d510f..ef1c1c1 100644
--- a/src/ikarus.fasl.write.ss
+++ b/src/ikarus.fasl.write.ss
@@ -10,18 +10,17 @@
   (define write-fixnum 
     (lambda (x p)
       (unless (fixnum? x) (error 'write-fixnum "not a fixnum ~s" x))
-      (write-char (integer->char (fxsll (fxlogand x #x3F) 2)) p)
-      (write-char (integer->char (fxlogand (fxsra x 6) #xFF)) p)
-      (write-char (integer->char (fxlogand (fxsra x 14) #xFF)) p)
-      (write-char (integer->char (fxlogand (fxsra x 22) #xFF)) p)))
+      (write-byte (fxsll (fxlogand x #x3F) 2) p)
+      (write-byte (fxlogand (fxsra x 6) #xFF) p)
+      (write-byte (fxlogand (fxsra x 14) #xFF) p)
+      (write-byte (fxlogand (fxsra x 22) #xFF) p)))
   (define write-int 
     (lambda (x p)
       (unless (fixnum? x) (error 'write-int "not a fixnum ~s" x))
-      (write-char (integer->char (fxlogand x #xFF)) p)
-      (write-char (integer->char (fxlogand (fxsra x 8) #xFF)) p)
-      (write-char (integer->char (fxlogand (fxsra x 16) #xFF)) p)
-      (write-char (integer->char (fxlogand (fxsra x 24) #xFF)) p)))
-  
+      (write-byte (fxlogand x #xFF) p)
+      (write-byte (fxlogand (fxsra x 8) #xFF) p)
+      (write-byte (fxlogand (fxsra x 16) #xFF) p)
+      (write-byte (fxlogand (fxsra x 24) #xFF) p)))
   (define fasl-write-immediate
     (lambda (x p)
       (cond
@@ -76,7 +75,7 @@
          (write-fixnum (code-freevars x) p)
          (let f ([i 0] [n (code-size x)])
            (unless (fx= i n)
-             (write-char (integer->char (code-ref x i)) p)
+             (write-byte (code-ref x i) p)
              (f (fxadd1 i) n)))
          (fasl-write-object (code-reloc-vector x) p h m)]
         [(record? x)
diff --git a/src/ikarus.io.output-files.ss b/src/ikarus.io.output-files.ss
index 28fb4e3..191a1f3 100644
--- a/src/ikarus.io.output-files.ss
+++ b/src/ikarus.io.output-files.ss
@@ -7,6 +7,8 @@
     (ikarus system $ports)
     (ikarus system $io)
     (ikarus system $strings)
+    (ikarus system $chars)
+    (ikarus system $bytevectors)
     (ikarus system $fx)
     (except (ikarus)
             standard-output-port standard-error-port   
@@ -48,7 +50,7 @@
            (close-output-port p)
            (close-ports))])))
 
-  (define do-write-buffer
+  (define do-write-buffer-old
     (lambda (fd port-name p caller)
       (let ([bytes (foreign-call "ikrt_write_file" 
                                  fd
@@ -58,7 +60,14 @@
             (set-port-output-index! p 0)
             (error caller "cannot write to file ~s: ~a" port-name bytes)))))
   
-  (define make-output-file-handler
+  (define do-write-buffer
+    (lambda (fd port-name buff idx caller)
+      (let ([bytes (foreign-call "ikrt_write_file" fd buff idx)])
+        (if (fixnum? bytes)
+            bytes
+            (error caller "cannot write to file ~s: ~a" port-name bytes)))))
+
+  (define make-output-file-handler-old
     (lambda (fd port-name)
       (define open? #t)
       (define output-file-handler
@@ -98,6 +107,56 @@
                          "unhandled message ~s" (cons msg args))])))
       output-file-handler))
   
+  (define make-output-file-handler
+    (lambda (fd port-name)
+      (define open? #t)
+      (define buff ($make-bytevector 4096))
+      (define idx 0)
+      (define size 4096)
+      (define output-file-handler
+        (lambda (msg . args)
+          (message-case msg args
+            [(write-byte b p)
+             (if (and (fixnum? b) ($fx<= 0 b) ($fx<= b 255))
+                 (if (output-port? p)
+                     (if ($fx< idx size)
+                         (begin
+                           ($bytevector-set! buff idx b)
+                           (set! idx ($fxadd1 idx)))
+                         (if open?
+                           (let ([bytes (do-write-buffer fd port-name buff idx 'write-char)])
+                             (set! idx 0)
+                             ($write-byte b p))
+                           (error 'write-byte "port ~s is closed" p)))
+                     (error 'write-byte "~s is not an output-port" p))
+                 (error 'write-byte "~s is not a byte" b))]
+            [(write-char c p)
+             (if (char? c)
+                 (if (output-port? p)
+                     (let ([b ($char->fixnum c)])
+                       (if ($fx<= b 255)
+                           ($write-byte b p)
+                           (error 'write-char "multibyte write of ~s not implemented" c)))
+                     (error 'write-char "~s is not an output-port" p))
+                 (error 'write-char "~s is not a character" c))]
+            [(flush-output-port p)
+             (if (output-port? p)
+                 (if open?
+                     (let ([bytes (do-write-buffer fd port-name buff idx 'flush-output-port)])
+                       (set! idx 0))
+                     (error 'flush-output-port "port ~s is closed" p))
+                 (error 'flush-output-port "~s is not an output-port" p))]
+            [(close-port p)
+             (when open?
+               (flush-output-port p)
+               (set! size 0)
+               (set! open? #f)
+               (unless (foreign-call "ikrt_close_file" fd)
+                 (error 'close-output-port "cannot close ~s" port-name)))]
+            [(port-name p) port-name]
+            [else (error 'output-file-handler 
+                         "unhandled message ~s" (cons msg args))])))
+      output-file-handler))
   (define (option-id x)
     (case x
       [(error)    0]
@@ -117,7 +176,7 @@
             (let ([port
                    (make-output-port
                      (make-output-file-handler fd/error filename)
-                     (make-string 4096))])
+                     (make-string 0))])
               (guardian port)
               port)
             (error 'open-output-file "cannot open ~s: ~a" filename fd/error)))))
@@ -191,9 +250,9 @@
   (set! *standard-output-port* 
     (make-output-port
       (make-output-file-handler 1 '*stdout*)
-      (make-string 4096)))
+      (make-string 0)))
   (set! *current-output-port* *standard-output-port*)
   (set! *standard-error-port* 
     (make-output-port
       (make-output-file-handler 2 '*stderr*)
-      (make-string 4096))) )
+      (make-string 0))) )
diff --git a/src/ikarus.io.output-strings.ss b/src/ikarus.io.output-strings.ss
index 52639fd..adb7219 100644
--- a/src/ikarus.io.output-strings.ss
+++ b/src/ikarus.io.output-strings.ss
@@ -3,6 +3,8 @@
   (export open-output-string get-output-string with-output-to-string)
   (import 
     (ikarus system $strings)
+    (ikarus system $bytevectors)
+    (ikarus system $chars)
     (ikarus system $fx)
     (ikarus system $pairs)
     (ikarus system $ports)
@@ -35,7 +37,7 @@
     (lambda (s)
       (substring s 0 (string-length s))))
 
-  (define concat 
+  (define concat-old
     (lambda (str i ls)
       (let ([n (sum i ls)])
         (let ([outstr (make-string n)])
@@ -45,13 +47,28 @@
                 (let ([a ($car ls)])
                   (f (copy outstr a (string-length a) n) ($cdr ls)))))))))
 
+  (define concat 
+    (lambda (bv i ls)
+      (let ([n (sum i ls)])
+        (let ([outstr (make-string n)])
+          (let f ([n (copy outstr bv i n)] [ls ls])
+            (if (null? ls)
+                outstr
+                (let ([a ($car ls)])
+                  (f (copy outstr a ($bytevector-length a) n) ($cdr ls)))))))))
   (define sum 
     (lambda (ac ls)
       (cond
         [(null? ls) ac]
-        [else (sum ($fx+ ac (string-length ($car ls))) ($cdr ls))])))
+        [else (sum ($fx+ ac ($bytevector-length ($car ls))) ($cdr ls))])))
   
-  (define copy
+  (define sum-old
+    (lambda (ac ls)
+      (cond
+        [(null? ls) ac]
+        [else (sum ($fx+ ac (string-length ($car ls))) ($cdr ls))])))
+
+  (define copy-old
     (lambda (dst src n end)
       (let f ([di end]
               [si n])
@@ -61,8 +78,21 @@
            (let ([di ($fxsub1 di)] [si ($fxsub1 si)])
              (string-set! dst di (string-ref src si))
              (f di si))]))))
-  
-  (define make-output-string-handler
+
+  (define copy
+    (lambda (dst src n end)
+      (let f ([di end]
+              [si n])
+        (cond
+          [($fx= si 0) di]
+          [else
+           (let ([di ($fxsub1 di)] [si ($fxsub1 si)])
+             (string-set! dst di 
+               (integer->char ($bytevector-u8-ref src si)))
+             (f di si))]))))
+
+
+  (define make-output-string-handler-old
     (lambda ()
       (define buffer-list '())
       (define open? #t)
@@ -102,11 +132,57 @@
                          "unhandled message ~s" (cons msg args))])))
       output-handler))
 
+  (define make-output-string-handler
+    (lambda ()
+      (define buffer-list '())
+      (define open? #t)
+      (define idx 0)
+      (define buff (make-bytevector 59))
+      (define size 59)
+      (define output-handler
+        (lambda (msg . args)
+          (message-case msg args
+            [(write-byte b p)
+             (if (and (fixnum? b) ($fx<= 0 b) ($fx<= b 255))
+                 (if (output-port? p)
+                     (if ($fx< idx size)
+                         (begin
+                           ($bytevector-set! buff idx b)
+                           (set! idx ($fxadd1 idx)))
+                         (if open?
+                           (begin
+                             (set! buffer-list (cons buff buffer-list))
+                             (set! buff (make-bytevector 59))
+                             ($bytevector-set! buff 0 b)
+                             (set! idx 1))
+                           (error 'write-byte "port ~s is closed" p)))
+                     (error 'write-byte "~s is not an output-port" p))
+                 (error 'write-byte "~s is not a byte" b))]
+            [(write-char c p)
+             (if (char? c)
+                 (if (output-port? p)
+                     (let ([b ($char->fixnum c)])
+                       (if ($fx<= b 255)
+                           ($write-byte b p)
+                           (error 'write-char "multibyte write of ~s is not implemented" c)))
+                     (error 'write-char "~s is not an output-port" p))
+                 (error 'write-char "~s is not a character" c))]
+            [(flush-output-port p)
+             (void)]
+            [(close-port p)
+             (set! open? #f)]
+            [(port-name p) 'string-port]
+            [(get-output-string p) 
+             (concat buff idx buffer-list)]
+            [else (error 'output-handler 
+                         "unhandled message ~s" (cons msg args))])))
+      output-handler))
+
   (define open-output-string 
     (lambda ()
       (make-output-port 
         (make-output-string-handler)
-        (make-string 10))))
+        (make-string 0))))
 
   (define get-output-string
     (lambda (p)