diff --git a/femtolisp/Makefile b/femtolisp/Makefile
index 2b9db26..7ee8a3e 100644
--- a/femtolisp/Makefile
+++ b/femtolisp/Makefile
@@ -1,7 +1,7 @@
 CC = gcc
 
 NAME = flisp
-SRCS = $(NAME).c builtins.c equal.c
+SRCS = $(NAME).c equal.c builtins.c string.c
 OBJS = $(SRCS:%.c=%.o)
 DOBJS = $(SRCS:%.c=%.do)
 EXENAME = $(NAME)
diff --git a/femtolisp/builtins.c b/femtolisp/builtins.c
index c4e8f7f..ce08b02 100644
--- a/femtolisp/builtins.c
+++ b/femtolisp/builtins.c
@@ -234,226 +234,6 @@ value_t fl_vector_alloc(value_t *args, u_int32_t nargs)
     return v;
 }
 
-int isstring(value_t v)
-{
-    return (iscvalue(v) && ((cvalue_t*)ptr(v))->flags.cstring);
-}
-
-value_t fl_intern(value_t *args, u_int32_t nargs)
-{
-    argcount("intern", nargs, 1);
-    if (!isstring(args[0]))
-        type_error("intern", "string", args[0]);
-    return symbol(cvalue_data(args[0]));
-}
-
-value_t fl_stringp(value_t *args, u_int32_t nargs)
-{
-    argcount("stringp", nargs, 1);
-    return isstring(args[0]) ? T : NIL;
-}
-
-value_t fl_string_length(value_t *args, u_int32_t nargs)
-{
-    argcount("string.length", nargs, 1);
-    if (!isstring(args[0]))
-        type_error("string.length", "string", args[0]);
-    size_t len = cv_len((cvalue_t*)ptr(args[0]));
-    return size_wrap(u8_charnum(cvalue_data(args[0]), len));
-}
-
-value_t fl_string_reverse(value_t *args, u_int32_t nargs)
-{
-    argcount("string.reverse", nargs, 1);
-    if (!isstring(args[0]))
-        type_error("string.reverse", "string", args[0]);
-    size_t len = cv_len((cvalue_t*)ptr(args[0]));
-    value_t ns = cvalue_string(len);
-    u8_reverse(cvalue_data(ns), cvalue_data(args[0]), len);
-    return ns;
-}
-
-value_t fl_string_encode(value_t *args, u_int32_t nargs)
-{
-    argcount("string.encode", nargs, 1);
-    if (iscvalue(args[0])) {
-        cvalue_t *cv = (cvalue_t*)ptr(args[0]);
-        value_t t = cv_type(cv);
-        if (iscons(t) && car_(t) == arraysym &&
-            iscons(cdr_(t)) && car_(cdr_(t)) == wcharsym) {
-            size_t nc = cv_len(cv) / sizeof(uint32_t);
-            uint32_t *ptr = (uint32_t*)cv_data(cv);
-            size_t nbytes = u8_codingsize(ptr, nc);
-            value_t str = cvalue_string(nbytes);
-            ptr = cv_data((cvalue_t*)ptr(args[0]));  // relocatable pointer
-            u8_toutf8(cvalue_data(str), nbytes, ptr, nc);
-            return str;
-        }
-    }
-    type_error("string.encode", "wide character array", args[0]);
-}
-
-value_t fl_string_decode(value_t *args, u_int32_t nargs)
-{
-    int term=0;
-    if (nargs == 2) {
-        term = (POP() != NIL);
-        nargs--;
-    }
-    argcount("string.decode", nargs, 1);
-    if (!isstring(args[0]))
-        type_error("string.decode", "string", args[0]);
-    cvalue_t *cv = (cvalue_t*)ptr(args[0]);
-    char *ptr = (char*)cv_data(cv);
-    size_t nb = cv_len(cv);
-    size_t nc = u8_charnum(ptr, nb);
-    size_t newsz = nc*sizeof(uint32_t);
-    if (term) newsz += sizeof(uint32_t);
-    value_t wcstr = cvalue(symbol_value(wcstringtypesym), newsz);
-    ptr = cv_data((cvalue_t*)ptr(args[0]));  // relocatable pointer
-    uint32_t *pwc = cvalue_data(wcstr);
-    u8_toucs(pwc, nc, ptr, nb);
-    if (term) pwc[nc] = 0;
-    return wcstr;
-}
-
-value_t fl_string(value_t *args, u_int32_t nargs)
-{
-    value_t cv, t;
-    u_int32_t i;
-    size_t len, sz = 0;
-    cvalue_t *temp;
-    char *data;
-    wchar_t wc;
-
-    for(i=0; i < nargs; i++) {
-        if (issymbol(args[i])) {
-            sz += strlen(symbol_name(args[i]));
-            continue;
-        }
-        else if (iscvalue(args[i])) {
-            temp = (cvalue_t*)ptr(args[i]);
-            t = cv_type(temp);
-            if (t == charsym) {
-                sz++;
-                continue;
-            }
-            else if (t == wcharsym) {
-                wc = *(wchar_t*)cv_data(temp);
-                sz += u8_charlen(wc);
-                continue;
-            }
-            else if (temp->flags.cstring) {
-                sz += cv_len(temp);
-                continue;
-            }
-        }
-        lerror(ArgError, "string: expected string, symbol or character");
-    }
-    cv = cvalue_string(sz);
-    char *ptr = cvalue_data(cv);
-    for(i=0; i < nargs; i++) {
-        if (issymbol(args[i])) {
-            char *name = symbol_name(args[i]);
-            while (*name) *ptr++ = *name++;
-        }
-        else {
-            temp = (cvalue_t*)ptr(args[i]);
-            t = cv_type(temp);
-            data = cvalue_data(args[i]);
-            if (t == charsym) {
-                *ptr++ = *(char*)data;
-            }
-            else if (t == wcharsym) {
-                ptr += u8_wc_toutf8(ptr, *(wchar_t*)data);
-            }
-            else {
-                len = cv_len(temp);
-                memcpy(ptr, data, len);
-                ptr += len;
-            }
-        }
-    }
-    return cv;
-}
-
-value_t fl_string_split(value_t *args, u_int32_t nargs)
-{
-    argcount("string.split", nargs, 2);
-    char *s = tostring(args[0], "string.split");
-    char *delim = tostring(args[1], "string.split");
-    size_t len = cv_len((cvalue_t*)ptr(args[0]));
-    size_t dlen = cv_len((cvalue_t*)ptr(args[1]));
-    PUSH(NIL);
-    size_t ssz, tokend=0, tokstart=0, i=0;
-    value_t c=NIL;
-    size_t junk;
-    do {
-        // find and allocate next token
-        tokstart = tokend = i;
-        while (i < len &&
-               !u8_memchr(delim, u8_nextmemchar(s, &i), dlen, &junk))
-            tokend = i;
-        ssz = tokend - tokstart;
-        PUSH(c);  // save previous cons cell
-        c = fl_cons(cvalue_string(ssz), NIL);
-
-        // we've done allocation; reload movable pointers
-        s = cv_data((cvalue_t*)ptr(args[0]));
-        delim = cv_data((cvalue_t*)ptr(args[1]));
-
-        if (ssz) memcpy(cv_data((cvalue_t*)ptr(car_(c))), &s[tokstart], ssz);
-
-        // link new cell
-        if (Stack[SP-1] == NIL) {
-            Stack[SP-2] = c;   // first time, save first cons
-            (void)POP();
-        }
-        else {
-            ((cons_t*)ptr(POP()))->cdr = c;
-        }
-
-        // note this tricky condition: if the string ends with a
-        // delimiter, we need to go around one more time to add an
-        // empty string. this happens when (i==len && tokend<i)
-    } while (i < len || (i==len && (tokend!=i)));
-    return POP();
-}
-
-value_t fl_string_sub(value_t *args, u_int32_t nargs)
-{
-    argcount("string.sub", nargs, 3);
-    char *s = tostring(args[0], "string.sub");
-    size_t len = cv_len((cvalue_t*)ptr(args[0]));
-    size_t i1, i2;
-    i1 = toulong(args[1], "string.sub");
-    if (i1 > len)
-        bounds_error("string.sub", args[0], args[1]);
-    i2 = toulong(args[2], "string.sub");
-    if (i2 > len)
-        bounds_error("string.sub", args[0], args[2]);
-    if (i2 <= i1)
-        return cvalue_string(0);
-    value_t ns = cvalue_string(i2-i1);
-    memcpy(cv_data((cvalue_t*)ptr(ns)), &s[i1], i2-i1);
-    return ns;
-}
-
-value_t fl_string_char(value_t *args, u_int32_t nargs)
-{
-    argcount("string.char", nargs, 2);
-    char *s = tostring(args[0], "string.char");
-    size_t len = cv_len((cvalue_t*)ptr(args[0]));
-    size_t i;
-    i = toulong(args[1], "string.char");
-    if (i > len)
-        bounds_error("string.char", args[0], args[1]);
-    size_t sl = u8_seqlen(&s[i]);
-    if (sl > len || i > len-sl)
-        bounds_error("string.char", args[0], args[1]);
-    return char_from_code(u8_nextchar(s, &i));
-}
-
 value_t fl_time_now(value_t *args, u_int32_t nargs)
 {
     argcount("time.now", nargs, 0);
@@ -559,6 +339,8 @@ value_t fl_randd(value_t *args, u_int32_t nargs)
     return mk_double(rand_double());
 }
 
+extern void stringfuncs_init();
+
 void builtins_init()
 {
     set(symbol("set-syntax"), guestfunc(fl_setsyntax));
@@ -572,22 +354,11 @@ void builtins_init()
     set(symbol("read"), guestfunc(fl_read));
     set(symbol("load"), guestfunc(fl_load));
     set(symbol("exit"), guestfunc(fl_exit));
-    set(symbol("intern"), guestfunc(fl_intern));
     set(symbol("fixnum"), guestfunc(fl_fixnum));
     set(symbol("truncate"), guestfunc(fl_truncate));
 
     set(symbol("vector.alloc"), guestfunc(fl_vector_alloc));
 
-    set(symbol("string"), guestfunc(fl_string));
-    set(symbol("stringp"), guestfunc(fl_stringp));
-    set(symbol("string.length"), guestfunc(fl_string_length));
-    set(symbol("string.split"), guestfunc(fl_string_split));
-    set(symbol("string.sub"), guestfunc(fl_string_sub));
-    set(symbol("string.char"), guestfunc(fl_string_char));
-    set(symbol("string.reverse"), guestfunc(fl_string_reverse));
-    set(symbol("string.encode"), guestfunc(fl_string_encode));
-    set(symbol("string.decode"), guestfunc(fl_string_decode));
-
     set(symbol("time.now"), guestfunc(fl_time_now));
     set(symbol("time.string"), guestfunc(fl_time_string));
 
@@ -600,4 +371,6 @@ void builtins_init()
 
     set(symbol("os.getenv"), guestfunc(fl_os_getenv));
     set(symbol("os.setenv"), guestfunc(fl_os_setenv));
+
+    stringfuncs_init();
 }
diff --git a/femtolisp/cvalues.c b/femtolisp/cvalues.c
index 5d07dd7..1e0b1d4 100644
--- a/femtolisp/cvalues.c
+++ b/femtolisp/cvalues.c
@@ -183,6 +183,11 @@ value_t cvalue_pinned_cstring(char *str)
     return v;
 }
 
+int isstring(value_t v)
+{
+    return (iscvalue(v) && ((cvalue_t*)ptr(v))->flags.cstring);
+}
+
 // convert to malloc representation (fixed address)
 /*
 static void cv_pin(cvalue_t *cv)
diff --git a/femtolisp/flisp.c b/femtolisp/flisp.c
index c48c95f..8eef772 100644
--- a/femtolisp/flisp.c
+++ b/femtolisp/flisp.c
@@ -397,7 +397,8 @@ static value_t relocate(value_t v)
     else if (iscvalue(v)) {
         return cvalue_relocate(v);
     }
-    else if (ismanaged(v) && issymbol(v)) {
+    else if (ismanaged(v)) {
+        assert(issymbol(v));
         gensym_t *gs = (gensym_t*)ptr(v);
         if (gs->id == 0xffffffff)
             return gs->binding;
diff --git a/femtolisp/string.c b/femtolisp/string.c
new file mode 100644
index 0000000..beda106
--- /dev/null
+++ b/femtolisp/string.c
@@ -0,0 +1,285 @@
+/*
+  string functions
+*/
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <setjmp.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <ctype.h>
+#include <sys/types.h>
+#include <sys/time.h>
+#include <errno.h>
+#include "llt.h"
+#include "flisp.h"
+
+value_t fl_intern(value_t *args, u_int32_t nargs)
+{
+    argcount("intern", nargs, 1);
+    if (!isstring(args[0]))
+        type_error("intern", "string", args[0]);
+    return symbol(cvalue_data(args[0]));
+}
+
+value_t fl_stringp(value_t *args, u_int32_t nargs)
+{
+    argcount("stringp", nargs, 1);
+    return isstring(args[0]) ? T : NIL;
+}
+
+value_t fl_string_length(value_t *args, u_int32_t nargs)
+{
+    argcount("string.length", nargs, 1);
+    if (!isstring(args[0]))
+        type_error("string.length", "string", args[0]);
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    return size_wrap(u8_charnum(cvalue_data(args[0]), len));
+}
+
+value_t fl_string_reverse(value_t *args, u_int32_t nargs)
+{
+    argcount("string.reverse", nargs, 1);
+    if (!isstring(args[0]))
+        type_error("string.reverse", "string", args[0]);
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    value_t ns = cvalue_string(len);
+    u8_reverse(cvalue_data(ns), cvalue_data(args[0]), len);
+    return ns;
+}
+
+value_t fl_string_encode(value_t *args, u_int32_t nargs)
+{
+    argcount("string.encode", nargs, 1);
+    if (iscvalue(args[0])) {
+        cvalue_t *cv = (cvalue_t*)ptr(args[0]);
+        value_t t = cv_type(cv);
+        if (iscons(t) && car_(t) == arraysym &&
+            iscons(cdr_(t)) && car_(cdr_(t)) == wcharsym) {
+            size_t nc = cv_len(cv) / sizeof(uint32_t);
+            uint32_t *ptr = (uint32_t*)cv_data(cv);
+            size_t nbytes = u8_codingsize(ptr, nc);
+            value_t str = cvalue_string(nbytes);
+            ptr = cv_data((cvalue_t*)ptr(args[0]));  // relocatable pointer
+            u8_toutf8(cvalue_data(str), nbytes, ptr, nc);
+            return str;
+        }
+    }
+    type_error("string.encode", "wide character array", args[0]);
+}
+
+value_t fl_string_decode(value_t *args, u_int32_t nargs)
+{
+    int term=0;
+    if (nargs == 2) {
+        term = (POP() != NIL);
+        nargs--;
+    }
+    argcount("string.decode", nargs, 1);
+    if (!isstring(args[0]))
+        type_error("string.decode", "string", args[0]);
+    cvalue_t *cv = (cvalue_t*)ptr(args[0]);
+    char *ptr = (char*)cv_data(cv);
+    size_t nb = cv_len(cv);
+    size_t nc = u8_charnum(ptr, nb);
+    size_t newsz = nc*sizeof(uint32_t);
+    if (term) newsz += sizeof(uint32_t);
+    value_t wcstr = cvalue(symbol_value(wcstringtypesym), newsz);
+    ptr = cv_data((cvalue_t*)ptr(args[0]));  // relocatable pointer
+    uint32_t *pwc = cvalue_data(wcstr);
+    u8_toucs(pwc, nc, ptr, nb);
+    if (term) pwc[nc] = 0;
+    return wcstr;
+}
+
+value_t fl_string(value_t *args, u_int32_t nargs)
+{
+    value_t cv, t;
+    u_int32_t i;
+    size_t len, sz = 0;
+    cvalue_t *temp;
+    char *data;
+    wchar_t wc;
+
+    for(i=0; i < nargs; i++) {
+        if (issymbol(args[i])) {
+            sz += strlen(symbol_name(args[i]));
+            continue;
+        }
+        else if (iscvalue(args[i])) {
+            temp = (cvalue_t*)ptr(args[i]);
+            t = cv_type(temp);
+            if (t == charsym) {
+                sz++;
+                continue;
+            }
+            else if (t == wcharsym) {
+                wc = *(wchar_t*)cv_data(temp);
+                sz += u8_charlen(wc);
+                continue;
+            }
+            else if (temp->flags.cstring) {
+                sz += cv_len(temp);
+                continue;
+            }
+        }
+        lerror(ArgError, "string: expected string, symbol or character");
+    }
+    cv = cvalue_string(sz);
+    char *ptr = cvalue_data(cv);
+    for(i=0; i < nargs; i++) {
+        if (issymbol(args[i])) {
+            char *name = symbol_name(args[i]);
+            while (*name) *ptr++ = *name++;
+        }
+        else {
+            temp = (cvalue_t*)ptr(args[i]);
+            t = cv_type(temp);
+            data = cvalue_data(args[i]);
+            if (t == charsym) {
+                *ptr++ = *(char*)data;
+            }
+            else if (t == wcharsym) {
+                ptr += u8_wc_toutf8(ptr, *(wchar_t*)data);
+            }
+            else {
+                len = cv_len(temp);
+                memcpy(ptr, data, len);
+                ptr += len;
+            }
+        }
+    }
+    return cv;
+}
+
+value_t fl_string_split(value_t *args, u_int32_t nargs)
+{
+    argcount("string.split", nargs, 2);
+    char *s = tostring(args[0], "string.split");
+    char *delim = tostring(args[1], "string.split");
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    size_t dlen = cv_len((cvalue_t*)ptr(args[1]));
+    PUSH(NIL);
+    size_t ssz, tokend=0, tokstart=0, i=0;
+    value_t c=NIL;
+    size_t junk;
+    do {
+        // find and allocate next token
+        tokstart = tokend = i;
+        while (i < len &&
+               !u8_memchr(delim, u8_nextmemchar(s, &i), dlen, &junk))
+            tokend = i;
+        ssz = tokend - tokstart;
+        PUSH(c);  // save previous cons cell
+        c = fl_cons(cvalue_string(ssz), NIL);
+
+        // we've done allocation; reload movable pointers
+        s = cv_data((cvalue_t*)ptr(args[0]));
+        delim = cv_data((cvalue_t*)ptr(args[1]));
+
+        if (ssz) memcpy(cv_data((cvalue_t*)ptr(car_(c))), &s[tokstart], ssz);
+
+        // link new cell
+        if (Stack[SP-1] == NIL) {
+            Stack[SP-2] = c;   // first time, save first cons
+            (void)POP();
+        }
+        else {
+            ((cons_t*)ptr(POP()))->cdr = c;
+        }
+
+        // note this tricky condition: if the string ends with a
+        // delimiter, we need to go around one more time to add an
+        // empty string. this happens when (i==len && tokend<i)
+    } while (i < len || (i==len && (tokend!=i)));
+    return POP();
+}
+
+value_t fl_string_sub(value_t *args, u_int32_t nargs)
+{
+    argcount("string.sub", nargs, 3);
+    char *s = tostring(args[0], "string.sub");
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    size_t i1, i2;
+    i1 = toulong(args[1], "string.sub");
+    if (i1 > len)
+        bounds_error("string.sub", args[0], args[1]);
+    i2 = toulong(args[2], "string.sub");
+    if (i2 > len)
+        bounds_error("string.sub", args[0], args[2]);
+    if (i2 <= i1)
+        return cvalue_string(0);
+    value_t ns = cvalue_string(i2-i1);
+    memcpy(cv_data((cvalue_t*)ptr(ns)), &s[i1], i2-i1);
+    return ns;
+}
+
+value_t fl_string_char(value_t *args, u_int32_t nargs)
+{
+    argcount("string.char", nargs, 2);
+    char *s = tostring(args[0], "string.char");
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    size_t i = toulong(args[1], "string.char");
+    if (i >= len)
+        bounds_error("string.char", args[0], args[1]);
+    size_t sl = u8_seqlen(&s[i]);
+    if (sl > len || i > len-sl)
+        bounds_error("string.char", args[0], args[1]);
+    return char_from_code(u8_nextchar(s, &i));
+}
+
+value_t fl_string_inc(value_t *args, u_int32_t nargs)
+{
+    if (nargs < 2 || nargs > 3)
+        argcount("string.inc", nargs, 2);
+    char *s = tostring(args[0], "string.inc");
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    size_t i = toulong(args[1], "string.inc");
+    size_t cnt = 1;
+    if (nargs == 3)
+        cnt = toulong(args[2], "string.inc");
+    while (cnt--) {
+        if (i >= len)
+            bounds_error("string.inc", args[0], args[1]);
+        u8_inc(s, &i);
+    }
+    return size_wrap(i);
+}
+
+value_t fl_string_dec(value_t *args, u_int32_t nargs)
+{
+    if (nargs < 2 || nargs > 3)
+        argcount("string.dec", nargs, 2);
+    char *s = tostring(args[0], "string.dec");
+    size_t len = cv_len((cvalue_t*)ptr(args[0]));
+    size_t i = toulong(args[1], "string.dec");
+    size_t cnt = 1;
+    if (nargs == 3)
+        cnt = toulong(args[2], "string.dec");
+    // note: i is allowed to start at index len
+    if (i > len)
+        bounds_error("string.dec", args[0], args[1]);
+    while (cnt--) {
+        if (i == 0)
+            bounds_error("string.dec", args[0], args[1]);
+        u8_dec(s, &i);
+    }
+    return size_wrap(i);
+}
+
+void stringfuncs_init()
+{
+    set(symbol("intern"), guestfunc(fl_intern));
+
+    set(symbol("string"), guestfunc(fl_string));
+    set(symbol("stringp"), guestfunc(fl_stringp));
+    set(symbol("string.length"), guestfunc(fl_string_length));
+    set(symbol("string.split"), guestfunc(fl_string_split));
+    set(symbol("string.sub"), guestfunc(fl_string_sub));
+    set(symbol("string.char"), guestfunc(fl_string_char));
+    set(symbol("string.inc"), guestfunc(fl_string_inc));
+    set(symbol("string.dec"), guestfunc(fl_string_dec));
+    set(symbol("string.reverse"), guestfunc(fl_string_reverse));
+    set(symbol("string.encode"), guestfunc(fl_string_encode));
+    set(symbol("string.decode"), guestfunc(fl_string_decode));
+}
diff --git a/femtolisp/todo b/femtolisp/todo
index 94f5514..5c69fd0 100644
--- a/femtolisp/todo
+++ b/femtolisp/todo
@@ -768,8 +768,8 @@ raise `(,e ,S). first argument e should be a symbol.
 String API
 
 *string         - append/construct
- string.inc     - (string.inc s i [nchars])
- string.dec
+*string.inc     - (string.inc s i [nchars])
+*string.dec
  string.count   - # of chars between 2 byte offsets
  string.width   - # columns
 *string.char    - char at byte offset
@@ -798,8 +798,8 @@ IOStream API
  stream.copy      - (stream.copy to from [nbytes])
  stream.copyuntil - (stream.copy to from byte)
  stream.flush
- stream.pos
- stream.seek
+ stream.pos       - (stream.pos s [set-pos])
+ stream.seek      - (stream.seek s offset)
  stream.trunc
  stream.getc      - get utf8 character(s)