diff --git a/src/libraries/libc/ctype.h b/src/libraries/libc/ctype.h
index 1388632..c4c2976 100644
--- a/src/libraries/libc/ctype.h
+++ b/src/libraries/libc/ctype.h
@@ -14,18 +14,50 @@
 extern "C" {
 #endif
 
-int isalnum( int ch );
-int isalpha( int ch );
-int islower( int ch );
-int isupper( int ch );
-int isdigit( int ch );
+enum {
+    __is_upper  = 0x001,
+    __is_lower  = 0x002,
+    __is_alpha  = 0x004,
+    __is_digit  = 0x008,
+    __is_xdigit = 0x010,
+    __is_space  = 0x020,
+    __is_print  = 0x040,
+    __is_graph  = 0x080,
+    __is_blank  = 0x100,
+    __is_cntrl  = 0x200,
+    __is_punct  = 0x400,
+    __is_alnum  = 0x800
+};
+
+
+int  isalnum( int ch );
+int  isalpha( int ch );
+int  islower( int ch );
+int  isupper( int ch );
+int  isdigit( int ch );
 int isxdigit( int ch );
-int iscntrl( int ch );
-int isgraph( int ch );
-int isspace( int ch );
-int isblank( int ch );
-int isprint( int ch );
-int ispunct( int ch );
+int  iscntrl( int ch );
+int  isgraph( int ch );
+int  isspace( int ch );
+int  isblank( int ch );
+int  isprint( int ch );
+int  ispunct( int ch );
+
+
+extern unsigned short *__ctype_b;
+#define __ctype_test(c, flag) (__ctype_b[(c)] | flag)
+#define  isalnum( ch ) __ctype_test(__is_alnum)
+#define  isalpha( ch ) __ctype_test(__is_alpha)
+#define  islower( ch ) __ctype_test(__is_lower)
+#define  isupper( ch ) __ctype_test(__is_upper)
+#define  isdigit( ch ) __ctype_test(__is_digit)
+#define isxdigit( ch ) __ctype_test(__is_xdigit)
+#define  iscntrl( ch ) __ctype_test(__is_cntrl)
+#define  isgraph( ch ) __ctype_test(__is_graph)
+#define  isspace( ch ) __ctype_test(__is_space)
+#define  isblank( ch ) __ctype_test(__is_blank)
+#define  isprint( ch ) __ctype_test(__is_print)
+#define  ispunct( ch ) __ctype_test(__is_punct)
 
 int tolower( int ch );
 int toupper( int ch );
diff --git a/src/libraries/libc/ctype/ctype_table.cpp b/src/libraries/libc/ctype/ctype_table.cpp
new file mode 100644
index 0000000..ec5b905
--- /dev/null
+++ b/src/libraries/libc/ctype/ctype_table.cpp
@@ -0,0 +1,78 @@
+#include <ctype.h>
+#include <stdint.h>
+
+namespace {
+
+// Only implemented for the "C" locale
+uint16_t locale_c_table[] = {
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+
+//    0     1     2     3     4     5     6     7     8     9     a     b     c     d     e     f
+    0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x1a0,0x0a0,0x0a0,0x0a0,0x0a0,0x200,0x200, // 0
+    0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200,0x200, // 1
+    0x160,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0, // 2
+    0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x8d8,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0, // 3
+    0x4a0,0x8d5,0x8d5,0x8d5,0x8d5,0x8d5,0x8d5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5, // 4
+    0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x8c5,0x4a0,0x4a0,0x4a0,0x4a0,0x4a0, // 5
+    0x4a0,0x8d6,0x8d6,0x8d6,0x8d6,0x8d6,0x8d6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6, // 6
+    0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x8c6,0x4a0,0x4a0,0x4a0,0x4a0,0x200, // 7
+
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+    0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,0x000,
+};
+
+
+} // namespace
+
+unsigned short *__ctype_b = locale_c_table + 128;
+
+extern "C" {
+
+const unsigned short **
+__ctype_b_loc(void)
+{
+    return (const unsigned short **)&__ctype_b;
+}
+
+#undef  isalnum( ch )
+#undef  isalpha( ch )
+#undef  islower( ch )
+#undef  isupper( ch )
+#undef  isdigit( ch )
+#undef isxdigit( ch )
+#undef  iscntrl( ch )
+#undef  isgraph( ch )
+#undef  isspace( ch )
+#undef  isblank( ch )
+#undef  isprint( ch )
+#undef  ispunct( ch )
+
+#define __ctype_impl(flag) int is##flag (int ch) { return __ctype_b[ch] | __is_##flag; }
+
+__ctype_impl(alnum)
+__ctype_impl(alpha)
+__ctype_impl(lower)
+__ctype_impl(upper)
+__ctype_impl(digit)
+__ctype_impl(xdigit)
+__ctype_impl(cntrl)
+__ctype_impl(graph)
+__ctype_impl(space)
+__ctype_impl(blank)
+__ctype_impl(print)
+__ctype_impl(punct)
+
+} // extern "C"
diff --git a/src/libraries/libc/ctype/isalnum.cpp b/src/libraries/libc/ctype/isalnum.cpp
deleted file mode 100644
index 00af2f0..0000000
--- a/src/libraries/libc/ctype/isalnum.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isalnum.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale
-
-int isalnum( int c ) {
-    return isalpha(c) || isdigit(c);
-}
diff --git a/src/libraries/libc/ctype/isalpha.cpp b/src/libraries/libc/ctype/isalpha.cpp
deleted file mode 100644
index 9d71b5f..0000000
--- a/src/libraries/libc/ctype/isalpha.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isalpha.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isalpha( int c ) {
-    return isupper(c) || islower(c);
-}
diff --git a/src/libraries/libc/ctype/isblank.cpp b/src/libraries/libc/ctype/isblank.cpp
deleted file mode 100644
index ede60ef..0000000
--- a/src/libraries/libc/ctype/isblank.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isblank.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isblank( int c ) {
-    return c == ' ' || c == '\t';
-}
diff --git a/src/libraries/libc/ctype/iscntrl.cpp b/src/libraries/libc/ctype/iscntrl.cpp
deleted file mode 100644
index 93bb5f0..0000000
--- a/src/libraries/libc/ctype/iscntrl.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file iscntrl.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int iscntrl( int c ) {
-    return (c < ' ') || (c > '~');
-}
diff --git a/src/libraries/libc/ctype/isdigit.cpp b/src/libraries/libc/ctype/isdigit.cpp
deleted file mode 100644
index bfc5ae3..0000000
--- a/src/libraries/libc/ctype/isdigit.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isdigit.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isdigit( int c ) {
-    return c >= '0' && c <= '9';
-}
diff --git a/src/libraries/libc/ctype/isgraph.cpp b/src/libraries/libc/ctype/isgraph.cpp
deleted file mode 100644
index 46ac78d..0000000
--- a/src/libraries/libc/ctype/isgraph.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isgraph.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isgraph( int c ) {
-    return isprint(c) && c != ' ';
-}
diff --git a/src/libraries/libc/ctype/islower.cpp b/src/libraries/libc/ctype/islower.cpp
deleted file mode 100644
index 3cd80d7..0000000
--- a/src/libraries/libc/ctype/islower.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file islower.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int islower( int c ) {
-    return c >= 'a' && c <= 'z';
-}
diff --git a/src/libraries/libc/ctype/isprint.cpp b/src/libraries/libc/ctype/isprint.cpp
deleted file mode 100644
index 3b5b52f..0000000
--- a/src/libraries/libc/ctype/isprint.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isprint.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isprint( int c ) {
-    return !iscntrl(c);
-}
diff --git a/src/libraries/libc/ctype/ispunct.cpp b/src/libraries/libc/ctype/ispunct.cpp
deleted file mode 100644
index ae885a1..0000000
--- a/src/libraries/libc/ctype/ispunct.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file ispunct.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int ispunct( int c ) {
-    return isgraph(c) && !isalnum(c);
-}
diff --git a/src/libraries/libc/ctype/isspace.cpp b/src/libraries/libc/ctype/isspace.cpp
deleted file mode 100644
index 83ba93f..0000000
--- a/src/libraries/libc/ctype/isspace.cpp
+++ /dev/null
@@ -1,27 +0,0 @@
-/** \file isspace.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isspace( int c ) {
-    switch (c) {
-        case '\t':
-        case '\n':
-        case '\v':
-        case '\f':
-        case '\r':
-        case ' ':
-            return true;
-        default:
-            return false;
-    }
-}
diff --git a/src/libraries/libc/ctype/isupper.cpp b/src/libraries/libc/ctype/isupper.cpp
deleted file mode 100644
index 6bae803..0000000
--- a/src/libraries/libc/ctype/isupper.cpp
+++ /dev/null
@@ -1,17 +0,0 @@
-/** \file isupper.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isupper( int c ) {
-    return c >= 'A' && c <= 'Z';
-}
diff --git a/src/libraries/libc/ctype/isxdigit.cpp b/src/libraries/libc/ctype/isxdigit.cpp
deleted file mode 100644
index a470f12..0000000
--- a/src/libraries/libc/ctype/isxdigit.cpp
+++ /dev/null
@@ -1,20 +0,0 @@
-/** \file isxdigit.cpp
-  *
-  * This file is part of the C standard library for the jsix operating
-  * system.
-  *
-  * This Source Code Form is subject to the terms of the Mozilla Public
-  * License, v. 2.0. If a copy of the MPL was not distributed with this
-  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
-  */
-
-#include <ctype.h>
-
-// Currently only implemented for "C" locale.
-
-int isxdigit( int c ) {
-    return
-        (c >= '0' && c <= '9') ||
-        (c >= 'A' && c <= 'F') ||
-        (c >= 'a' && c <= 'f');
-}