diff --git a/src/init.c b/src/init.c
index 040b100a..637e4a2b 100644
--- a/src/init.c
+++ b/src/init.c
@@ -25,6 +25,7 @@ void pic_init_str(pic_state *);
 void pic_init_macro(pic_state *);
 void pic_init_var(pic_state *);
 void pic_init_load(pic_state *);
+void pic_init_write(pic_state *);
 
 void
 pic_load_stdlib(pic_state *pic)
@@ -115,6 +116,7 @@ pic_init_core(pic_state *pic)
   pic_init_macro(pic); DONE;
   pic_init_var(pic); DONE;
   pic_init_load(pic); DONE;
+  pic_init_write(pic); DONE;
 
   /* native VM procedures */
   register_renamed_symbol(pic, rCONS, "cons");
diff --git a/src/port.c b/src/port.c
index 4241f3e8..13176bf4 100644
--- a/src/port.c
+++ b/src/port.c
@@ -6,8 +6,6 @@
 #include "picrin.h"
 #include "picrin/proc.h"
 #include "picrin/port.h"
-#include "picrin/blob.h"
-#include "picrin/macro.h"
 
 pic_value
 pic_eof_object()
@@ -272,154 +270,6 @@ pic_fputs(const char *str, pic_file *file)
   return 0;
 }
 
-static void write_pair(pic_state *pic, struct pic_pair *pair);
-static void write_str(pic_state *pic, struct pic_string *str);
-
-static void
-write(pic_state *pic, pic_value obj)
-{
-  int i;
-
-  switch (pic_type(obj)) {
-  case PIC_TT_NIL:
-    printf("()");
-    break;
-  case PIC_TT_BOOL:
-    if (pic_true_p(obj))
-      printf("#t");
-    else
-      printf("#f");
-    break;
-  case PIC_TT_PAIR:
-    printf("(");
-    write_pair(pic, pic_pair_ptr(obj));
-    printf(")");
-    break;
-  case PIC_TT_SYMBOL:
-    printf("%s", pic_symbol_name(pic, pic_sym(obj)));
-    break;
-  case PIC_TT_CHAR:
-    switch (pic_char(obj)) {
-    default: printf("#\\%c", pic_char(obj)); break;
-    case '\a': printf("#\\alarm"); break;
-    case '\b': printf("#\\backspace"); break;
-    case 0x7f: printf("#\\delete"); break;
-    case 0x1b: printf("#\\escape"); break;
-    case '\n': printf("#\\newline"); break;
-    case '\r': printf("#\\return"); break;
-    case ' ': printf("#\\space"); break;
-    case '\t': printf("#\\tab"); break;
-    }
-    break;
-  case PIC_TT_FLOAT:
-    printf("%f", pic_float(obj));
-    break;
-  case PIC_TT_INT:
-    printf("%d", pic_int(obj));
-    break;
-  case PIC_TT_EOF:
-    printf("#<eof-object>");
-    break;
-  case PIC_TT_UNDEF:
-    printf("#<undef>");
-    break;
-  case PIC_TT_PROC:
-    printf("#<proc %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_PORT:
-    printf("#<port %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_STRING:
-    printf("\"");
-    write_str(pic, pic_str_ptr(obj));
-    printf("\"");
-    break;
-  case PIC_TT_VECTOR:
-    printf("#(");
-    for (i = 0; i < pic_vec_ptr(obj)->len; ++i) {
-      write(pic, pic_vec_ptr(obj)->data[i]);
-      if (i + 1 < pic_vec_ptr(obj)->len) {
-	printf(" ");
-      }
-    }
-    printf(")");
-    break;
-  case PIC_TT_BLOB:
-    printf("#u8(");
-    for (i = 0; i < pic_blob_ptr(obj)->len; ++i) {
-      printf("%d", pic_blob_ptr(obj)->data[i]);
-      if (i + 1 < pic_blob_ptr(obj)->len) {
-	printf(" ");
-      }
-    }
-    printf(")");
-    break;
-  case PIC_TT_ERROR:
-    printf("#<error %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_ENV:
-    printf("#<env %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_CONT:
-    printf("#<cont %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_SENV:
-    printf("#<senv %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_SYNTAX:
-    printf("#<syntax %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_SC:
-    printf("#<sc %p: ", pic_ptr(obj));
-    write(pic, pic_sc(obj)->expr);
-    printf(">");
-    break;
-  case PIC_TT_LIB:
-    printf("#<library %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_VAR:
-    printf("#<var %p>", pic_ptr(obj));
-    break;
-  }
-}
-
-static void
-write_pair(pic_state *pic, struct pic_pair *pair)
-{
-  write(pic, pair->car);
-
-  if (pic_nil_p(pair->cdr)) {
-    return;
-  }
-  if (pic_pair_p(pair->cdr)) {
-    printf(" ");
-    write_pair(pic, pic_pair_ptr(pair->cdr));
-    return;
-  }
-  printf(" . ");
-  write(pic, pair->cdr);
-}
-
-static void
-write_str(pic_state *pic, struct pic_string *str)
-{
-  int i;
-  const char *cstr = str->str;
-
-  for (i = 0; i < str->len; ++i) {
-    if (cstr[i] == '"' || cstr[i] == '\\') {
-      putchar('\\');
-    }
-    putchar(cstr[i]);
-  }
-}
-
-void
-pic_debug(pic_state *pic, pic_value obj)
-{
-  write(pic, obj);
-}
-
 static pic_value
 port_new_from_fp(pic_state *pic, FILE *fp, short flags)
 {
@@ -644,16 +494,6 @@ pic_port_peek_char(pic_state *pic)
   }
 }
 
-static pic_value
-pic_port_write_simple(pic_state *pic)
-{
-  pic_value v;
-
-  pic_get_args(pic, "o", &v);
-  write(pic, v);
-  return pic_none_value();
-}
-
 static pic_value
 pic_port_newline(pic_state *pic)
 {
@@ -722,10 +562,4 @@ pic_init_port(pic_state *pic)
   pic_defun(pic, "newline", pic_port_newline);
   pic_defun(pic, "write-char", pic_port_write_char);
   pic_defun(pic, "flush-output-port", pic_port_flush);
-
-  DEFLIBRARY(pic, "(scheme write)")
-  {
-    pic_defun(pic, "write-simple", pic_port_write_simple);
-  }
-  ENDLIBRARY(pic);
 }
diff --git a/src/write.c b/src/write.c
new file mode 100644
index 00000000..7ea9b5fa
--- /dev/null
+++ b/src/write.c
@@ -0,0 +1,173 @@
+#include "picrin.h"
+#include "picrin/port.h"
+#include "picrin/pair.h"
+#include "picrin/blob.h"
+#include "picrin/macro.h"
+
+static void write_pair(pic_state *pic, struct pic_pair *pair);
+static void write_str(pic_state *pic, struct pic_string *str);
+
+static void
+write(pic_state *pic, pic_value obj)
+{
+  int i;
+
+  switch (pic_type(obj)) {
+  case PIC_TT_NIL:
+    printf("()");
+    break;
+  case PIC_TT_BOOL:
+    if (pic_true_p(obj))
+      printf("#t");
+    else
+      printf("#f");
+    break;
+  case PIC_TT_PAIR:
+    printf("(");
+    write_pair(pic, pic_pair_ptr(obj));
+    printf(")");
+    break;
+  case PIC_TT_SYMBOL:
+    printf("%s", pic_symbol_name(pic, pic_sym(obj)));
+    break;
+  case PIC_TT_CHAR:
+    switch (pic_char(obj)) {
+    default: printf("#\\%c", pic_char(obj)); break;
+    case '\a': printf("#\\alarm"); break;
+    case '\b': printf("#\\backspace"); break;
+    case 0x7f: printf("#\\delete"); break;
+    case 0x1b: printf("#\\escape"); break;
+    case '\n': printf("#\\newline"); break;
+    case '\r': printf("#\\return"); break;
+    case ' ': printf("#\\space"); break;
+    case '\t': printf("#\\tab"); break;
+    }
+    break;
+  case PIC_TT_FLOAT:
+    printf("%f", pic_float(obj));
+    break;
+  case PIC_TT_INT:
+    printf("%d", pic_int(obj));
+    break;
+  case PIC_TT_EOF:
+    printf("#<eof-object>");
+    break;
+  case PIC_TT_UNDEF:
+    printf("#<undef>");
+    break;
+  case PIC_TT_PROC:
+    printf("#<proc %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_PORT:
+    printf("#<port %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_STRING:
+    printf("\"");
+    write_str(pic, pic_str_ptr(obj));
+    printf("\"");
+    break;
+  case PIC_TT_VECTOR:
+    printf("#(");
+    for (i = 0; i < pic_vec_ptr(obj)->len; ++i) {
+      write(pic, pic_vec_ptr(obj)->data[i]);
+      if (i + 1 < pic_vec_ptr(obj)->len) {
+	printf(" ");
+      }
+    }
+    printf(")");
+    break;
+  case PIC_TT_BLOB:
+    printf("#u8(");
+    for (i = 0; i < pic_blob_ptr(obj)->len; ++i) {
+      printf("%d", pic_blob_ptr(obj)->data[i]);
+      if (i + 1 < pic_blob_ptr(obj)->len) {
+	printf(" ");
+      }
+    }
+    printf(")");
+    break;
+  case PIC_TT_ERROR:
+    printf("#<error %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_ENV:
+    printf("#<env %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_CONT:
+    printf("#<cont %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_SENV:
+    printf("#<senv %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_SYNTAX:
+    printf("#<syntax %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_SC:
+    printf("#<sc %p: ", pic_ptr(obj));
+    write(pic, pic_sc(obj)->expr);
+    printf(">");
+    break;
+  case PIC_TT_LIB:
+    printf("#<library %p>", pic_ptr(obj));
+    break;
+  case PIC_TT_VAR:
+    printf("#<var %p>", pic_ptr(obj));
+    break;
+  }
+}
+
+static void
+write_pair(pic_state *pic, struct pic_pair *pair)
+{
+  write(pic, pair->car);
+
+  if (pic_nil_p(pair->cdr)) {
+    return;
+  }
+  if (pic_pair_p(pair->cdr)) {
+    printf(" ");
+    write_pair(pic, pic_pair_ptr(pair->cdr));
+    return;
+  }
+  printf(" . ");
+  write(pic, pair->cdr);
+}
+
+static void
+write_str(pic_state *pic, struct pic_string *str)
+{
+  int i;
+  const char *cstr = str->str;
+
+  for (i = 0; i < str->len; ++i) {
+    if (cstr[i] == '"' || cstr[i] == '\\') {
+      putchar('\\');
+    }
+    putchar(cstr[i]);
+  }
+}
+
+void
+pic_debug(pic_state *pic, pic_value obj)
+{
+  write(pic, obj);
+}
+
+static pic_value
+pic_port_write_simple(pic_state *pic)
+{
+  pic_value v;
+
+  pic_get_args(pic, "o", &v);
+  write(pic, v);
+  return pic_none_value();
+}
+
+void
+pic_init_write(pic_state *pic)
+{
+  DEFLIBRARY(pic, "(scheme write)")
+  {
+    pic_defun(pic, "write-simple", pic_port_write_simple);
+  }
+  ENDLIBRARY(pic);
+}