diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 70bf59ca..18553a08 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -1,5 +1,13 @@
 set(SOURCES 
     src/main.cpp
+    src/string.cpp
+    src/arch/Serial.cpp
+)
+
+set(SOURCES
+    ${SOURCES}
+    src/arch/x86_64/IO.cpp
+    src/arch/x86_64/Serial.cpp
 )
 
 add_compile_options(-Os)
@@ -20,6 +28,7 @@ add_link_options(-lgcc -Wl,--build-id=none -z max-page-size=0x1000 -mno-red-zone
 add_executable(moon ${SOURCES})
 
 target_include_directories(moon PUBLIC ${LUNA_ROOT}/luna)
+target_include_directories(moon PRIVATE ${CMAKE_CURRENT_LIST_DIR}/src)
 
 target_link_options(moon PRIVATE LINKER:-T ${CMAKE_CURRENT_LIST_DIR}/moon.ld -nostdlib -nodefaultlibs)
 
diff --git a/kernel/src/arch/Serial.cpp b/kernel/src/arch/Serial.cpp
new file mode 100644
index 00000000..958557f6
--- /dev/null
+++ b/kernel/src/arch/Serial.cpp
@@ -0,0 +1,20 @@
+#include "arch/Serial.h"
+
+namespace Serial
+{
+    void write(const char* str, size_t size)
+    {
+        while (size--) putchar(*str++);
+    }
+
+    void print(const char* str)
+    {
+        while (*str) putchar(*str++);
+    }
+
+    void println(const char* str)
+    {
+        print(str);
+        putchar('\n');
+    }
+}
\ No newline at end of file
diff --git a/kernel/src/arch/Serial.h b/kernel/src/arch/Serial.h
new file mode 100644
index 00000000..031aaac0
--- /dev/null
+++ b/kernel/src/arch/Serial.h
@@ -0,0 +1,10 @@
+#pragma once
+#include <Types.h>
+
+namespace Serial
+{
+    void putchar(u8 c);
+    void write(const char* str, size_t size);
+    void print(const char* str);
+    void println(const char* str);
+}
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/IO.cpp b/kernel/src/arch/x86_64/IO.cpp
new file mode 100644
index 00000000..8afa0a08
--- /dev/null
+++ b/kernel/src/arch/x86_64/IO.cpp
@@ -0,0 +1,40 @@
+#include "arch/x86_64/IO.h"
+
+namespace IO
+{
+    u8 inb(u16 port)
+    {
+        u8 result;
+        asm volatile("inb %1, %0" : "=a"(result) : "Nd"(port));
+        return result;
+    }
+
+    void outb(u16 port, u8 value)
+    {
+        asm volatile("outb %0, %1" : : "a"(value), "Nd"(port));
+    }
+
+    u16 inw(u16 port)
+    {
+        u16 result;
+        asm volatile("inw %1, %0" : "=a"(result) : "Nd"(port));
+        return result;
+    }
+
+    void outw(u16 port, u16 value)
+    {
+        asm volatile("outw %0, %1" : : "a"(value), "Nd"(port));
+    }
+
+    u32 inl(u16 port)
+    {
+        u32 result;
+        asm volatile("inl %1, %0" : "=a"(result) : "Nd"(port));
+        return result;
+    }
+
+    void outl(u16 port, u32 value)
+    {
+        asm volatile("outl %0, %1" : : "a"(value), "Nd"(port));
+    }
+}
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/IO.h b/kernel/src/arch/x86_64/IO.h
new file mode 100644
index 00000000..05c6acf9
--- /dev/null
+++ b/kernel/src/arch/x86_64/IO.h
@@ -0,0 +1,13 @@
+#pragma once
+#include <Types.h>
+
+namespace IO
+{
+    u8 inb(u16 port);
+    u16 inw(u16 port);
+    u32 inl(u16 port);
+
+    void outb(u16 port, u8 value);
+    void outw(u16 port, u16 value);
+    void outl(u16 port, u32 value);
+}
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/Serial.cpp b/kernel/src/arch/x86_64/Serial.cpp
new file mode 100644
index 00000000..3dc26ec4
--- /dev/null
+++ b/kernel/src/arch/x86_64/Serial.cpp
@@ -0,0 +1,15 @@
+#include "arch/Serial.h"
+#include "arch/x86_64/IO.h"
+
+#define COM1 0x3f8
+
+static void serial_wait()
+{
+    while (!(IO::inb(COM1 + 5) & 0x20)) { asm volatile("pause"); }
+}
+
+void Serial::putchar(u8 c)
+{
+    serial_wait();
+    IO::outb(COM1, c);
+}
\ No newline at end of file
diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index abf41426..3b529072 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -1,7 +1,9 @@
-#include <Types.h>
+#include "arch/Serial.h"
 
 extern "C" void _start()
 {
+    Serial::println("Hello, world!");
+
     for (;;)
         ;
 }
\ No newline at end of file
diff --git a/kernel/src/string.cpp b/kernel/src/string.cpp
new file mode 100644
index 00000000..68167cd2
--- /dev/null
+++ b/kernel/src/string.cpp
@@ -0,0 +1,5 @@
+extern "C"
+{
+#define _LUNA_IMPLEMENTATION
+#include <String.h>
+}
\ No newline at end of file
diff --git a/luna/String.h b/luna/String.h
new file mode 100644
index 00000000..bba602be
--- /dev/null
+++ b/luna/String.h
@@ -0,0 +1,65 @@
+#pragma once
+#include <Types.h>
+
+void* memcpy(void* dest, const void* src, size_t n)
+#ifdef _LUNA_IMPLEMENTATION
+{
+    for (size_t i = 0; i < n; ++i) { *((u8*)dest + i) = *((const u8*)src + i); }
+    return dest;
+}
+#else
+    ;
+#endif
+
+void* memset(void* buf, int c, size_t n)
+#ifdef _LUNA_IMPLEMENTATION
+{
+    for (size_t i = 0; i < n; ++i) { *((u8*)buf + i) = (u8)c; }
+    return buf;
+}
+#else
+    ;
+#endif
+
+int memcmp(const void* a, const void* b, size_t n)
+#ifdef _LUNA_IMPLEMENTATION
+{
+    if (!n) return 0;
+    const u8* ap = (const u8*)a;
+    const u8* bp = (const u8*)b;
+    while (--n && *ap == *bp)
+    {
+        ap++;
+        bp++;
+    }
+    return *ap - *bp;
+}
+#else
+    ;
+#endif
+
+void* memmove(void* dest, const void* src, size_t n)
+#ifdef _LUNA_IMPLEMENTATION
+{
+    if (dest == src) return dest;
+    if (dest > src)
+        for (long i = n - 1; i >= 0; i++) { *((u8*)dest + i) = *((const u8*)src + i); }
+    else
+        for (long i = 0; i < (long)n; i++) { *((u8*)dest + i) = *((const u8*)src + i); }
+    return dest;
+}
+#else
+    ;
+#endif
+
+size_t strlen(const char* str)
+#ifdef _LUNA_IMPLEMENTATION
+{
+    const char* i = str;
+    for (; *i; ++i)
+        ;
+    return (i - str);
+}
+#else
+    ;
+#endif
\ No newline at end of file
diff --git a/luna/Types.h b/luna/Types.h
index d2dc477b..c45e4448 100644
--- a/luna/Types.h
+++ b/luna/Types.h
@@ -1,3 +1,4 @@
+#include <stddef.h>
 #include <stdint.h>
 
 typedef uint8_t u8;