diff --git a/kernel/Makefile b/kernel/Makefile
index 7256072..ab1e072 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -13,7 +13,7 @@ export CFLAGS   := -Wall -O2
 export CXXFLAGS := -Wall -O2 -fno-rtti -fno-exceptions
 export LDFLAGS  := -T $(LDSCRIPT) -Map $(KERNEL).map
 
-SUBDIRS         := boot mm
+SUBDIRS         := boot mm lang
 SUBDIRS_clean   := $(SUBDIRS:%=%.clean)
 
 .PHONY: all
diff --git a/kernel/lang/Makefile b/kernel/lang/Makefile
new file mode 100644
index 0000000..cae81d7
--- /dev/null
+++ b/kernel/lang/Makefile
@@ -0,0 +1,2 @@
+
+include $(HOS_TOPLEVEL)/subdir.mak
diff --git a/kernel/lang/kio.cc b/kernel/lang/kio.cc
new file mode 100644
index 0000000..227d76c
--- /dev/null
+++ b/kernel/lang/kio.cc
@@ -0,0 +1,157 @@
+
+#include "kio.h"
+#include "string.h"
+
+#include <stdarg.h>                 /* va_*() */
+
+static void fmt_d2a(char * buf, int val);
+static void fmt_u2a(char * buf, unsigned int val);
+static void fmt_ll2a(char * buf, long long val);
+static void fmt_ull2a(char * buf, unsigned long long val);
+static void fmt_x2a(char * buf, unsigned int val);
+static void fmt_o2a(char * buf, unsigned int val);
+
+extern "C" {
+
+void kprintf(char * fmt, ...)
+{
+    va_list args;
+    va_start(args, fmt);
+
+    kvprintf(fmt, args);
+
+    va_end(args);
+}
+
+void kvprintf(char * fmt, va_list args)
+{
+    char tmpbuf[25];
+    for ( ; *fmt; fmt++)
+    {
+        if (*fmt == '%')
+        {
+            fmt++;
+            if (*fmt)
+            {
+                switch (*fmt)
+                {
+                    case 'c':
+                        kputc(va_arg(args, int));
+                        break;
+                    case 'd':
+                        fmt_d2a(tmpbuf, va_arg(args, int));
+                        kputs(tmpbuf);
+                        break;
+                    case 'l':
+                        fmt_ll2a(tmpbuf, va_arg(args, long long));
+                        kputs(tmpbuf);
+                        break;
+                    case 'L':
+                        fmt_ull2a(tmpbuf, va_arg(args, unsigned long long));
+                        kputs(tmpbuf);
+                        break;
+                    case 'o':
+                        fmt_o2a(tmpbuf, va_arg(args, unsigned int));
+                        kputs(tmpbuf);
+                        break;
+                    case 's':
+                        kputs(va_arg(args, char *));
+                        break;
+                    case 'u':
+                        fmt_u2a(tmpbuf, va_arg(args, unsigned int));
+                        kputs(tmpbuf);
+                        break;
+                    case 'x':
+                        fmt_x2a(tmpbuf, va_arg(args, unsigned int));
+                        kputs(tmpbuf);
+                        break;
+                    case '%':
+                        kputc('%');
+                        break;
+                }
+            }
+        }
+        else
+        {
+            kputc(*fmt);
+        }
+    }
+}
+
+void kputc(char c)
+{
+}
+
+void kputs(char * s)
+{
+    while (*s)
+    {
+        kputc(*s);
+        s++;
+    }
+}
+
+} /* extern "C" */
+
+static void fmt_d2a(char * buf, int val)
+{
+    if (val == 0x7FFFFFFF)
+    {
+        strcpy(buf, "-2147483648");
+    }
+    else
+    {
+        if (val < 0)
+        {
+            *buf++ = '-';
+            val = -val;
+        }
+        fmt_u2a(buf, (unsigned int) val);
+    }
+}
+
+static void fmt_u2a(char * buf, unsigned int val)
+{
+}
+
+static void fmt_ll2a(char * buf, long long val)
+{
+}
+
+static void fmt_ull2a(char * buf, unsigned long long val)
+{
+}
+
+static void fmt_x2a(char * buf, unsigned int val)
+{
+    bool printing = false;
+    for (int s = 28; s >= 0; s -= 4)
+    {
+        unsigned int n = (val >> s) & 0xF;
+        if (n)
+        {
+            printing = true;
+        }
+        if (printing)
+        {
+            *buf++ = "0123456789ABCDEF"[n];
+        }
+    }
+}
+
+static void fmt_o2a(char * buf, unsigned int val)
+{
+    bool printing = false;
+    for (int s = 30; s >= 0; s -= 3)
+    {
+        unsigned int n = (val >> s) & 0x7;
+        if (n)
+        {
+            printing = true;
+        }
+        if (printing)
+        {
+            *buf++ = "01234567"[n];
+        }
+    }
+}
diff --git a/kernel/lang/kio.h b/kernel/lang/kio.h
new file mode 100644
index 0000000..7916f0b
--- /dev/null
+++ b/kernel/lang/kio.h
@@ -0,0 +1,23 @@
+
+#ifndef KIO_H
+#define KIO_H
+
+#include <stdarg.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void kprintf(char * fmt, ...);
+
+void kvprintf(char * fmt, va_list args);
+
+void kputc(char c);
+
+void kputs(char * s);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
diff --git a/kernel/lang/string.cc b/kernel/lang/string.cc
new file mode 100644
index 0000000..8614fd9
--- /dev/null
+++ b/kernel/lang/string.cc
@@ -0,0 +1,14 @@
+
+#include "string.h"
+
+extern "C" {
+
+void strcpy(char * dst, const char * src)
+{
+    while (*src)
+    {
+        *dst++ = *src++;
+    }
+}
+
+} /* extern "C" */
diff --git a/kernel/lang/string.h b/kernel/lang/string.h
new file mode 100644
index 0000000..7505167
--- /dev/null
+++ b/kernel/lang/string.h
@@ -0,0 +1,15 @@
+
+#ifndef STRING_H
+#define STRING_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void strcpy(char * dst, const char * src);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif