diff --git a/.clangd b/.clangd
index 4ec85cd..5467e39 100644
--- a/.clangd
+++ b/.clangd
@@ -1,3 +1,3 @@
 CompileFlags:
   Add: 
-    - -DOS_WINDOWS
+    - -DOS_LINUX
diff --git a/core.cpp b/core.cpp
index efa4328..7320438 100644
--- a/core.cpp
+++ b/core.cpp
@@ -1,5 +1,6 @@
 #define STB_SPRINTF_IMPLEMENTATION
 #include "core.h"
+#include "os.h"
 
 void *pushSize(Arena *arena, size_t bytes) {
     if (arena->capacity - arena->head >= bytes) {
@@ -11,11 +12,7 @@ void *pushSize(Arena *arena, size_t bytes) {
 }
 
 Arena *arenaAlloc(size_t capacity) {
-#if OS_WINDOWS 
-    Arena *result = (Arena *)VirtualAlloc(NULL, sizeof(Arena) + capacity, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
-#elif OS_LINUX
-    Arena *result = (Arena *)mmap(0, capacity, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-#endif
+    Arena *result = (Arena *)os_alloc(sizeof(Arena) + capacity);
     result->memory = result + sizeof(Arena);
     result->capacity = capacity;
     result->head = 0;
@@ -23,6 +20,7 @@ Arena *arenaAlloc(size_t capacity) {
 }
 
 void arenaFree(Arena *arena) {
+    os_free(arena);
 #if OS_WINDOWS 
     VirtualFree(arena, NULL, MEM_RELEASE);
 #elif OS_LINUX
@@ -315,9 +313,9 @@ string readEntireFile(Arena *arena, string filename) {
     }
     return result;
 #elif OS_LINUX
-    FILE *input = fopen((char *)file.str, "r");
+    FILE *input = fopen((char *)filename.str, "r");
     struct stat st;
-    stat((char *)file.str, &st);
+    stat((char *)filename.str, &st);
     size_t fsize = st.st_size;
     string readBuffer = PushString(arena, filesize);
     readBuffer.length = filesize;
diff --git a/core.h b/core.h
index 55fe41a..7ff357b 100644
--- a/core.h
+++ b/core.h
@@ -7,15 +7,6 @@
 #include <stdio.h>
 #include <time.h> // TODO(dledda): try not to depend on this one
 
-#if OS_WINDOWS
-    #include "Windows.h" 
-#elif OS_LINUX
-    #include <sys/mman.h>
-    #include <sys/stat.h>
-#else 
-    #error Development environment not supported.
-#endif
-
 // ### Misc macros ### 
 #if ENABLE_ASSERT
 #define Assert(expression) if (!(expression)) {*(volatile int *)0 = 0;}
diff --git a/os.cpp b/os.cpp
new file mode 100644
index 0000000..64a2575
--- /dev/null
+++ b/os.cpp
@@ -0,0 +1,12 @@
+#ifndef OS_CPP
+#define OS_CPP
+
+#if OS_WINDOWS
+#include "os_win32.cpp"
+#elif OS_LINUX
+#include "os_linux.cpp"
+#else 
+    #error Development environment not supported.
+#endif
+
+#endif
diff --git a/os.h b/os.h
new file mode 100644
index 0000000..e23818f
--- /dev/null
+++ b/os.h
@@ -0,0 +1,12 @@
+#ifndef OS_H
+#define OS_H
+
+#include "core.h"
+
+// ### Memory ###
+void *os_alloc(size_t capacity);
+void os_reserve(void *ptr);
+void os_decommit(void *ptr);
+void os_free(void *ptr);
+
+#endif
diff --git a/os_linux.cpp b/os_linux.cpp
new file mode 100644
index 0000000..0ca6a11
--- /dev/null
+++ b/os_linux.cpp
@@ -0,0 +1,21 @@
+#ifndef OS_IMPL_LINUX_CPP
+#define OS_IMPL_LINUX_CPP
+
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include "os.h"
+
+void *os_alloc(size_t capacity) {
+    return mmap(0, capacity, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+}
+
+void os_reserve(void *ptr) {
+}
+
+void os_decommit(void *ptr) {
+}
+
+void os_free(void *ptr) {
+}
+
+#endif
diff --git a/os_win32.cpp b/os_win32.cpp
new file mode 100644
index 0000000..46fc5ef
--- /dev/null
+++ b/os_win32.cpp
@@ -0,0 +1,20 @@
+#ifndef OS_IMPL_WIN32_CPP
+#define OS_IMPL_WIN32_CPP
+
+#include "os.h"
+#include "Windows.h" 
+
+void *osAlloc(size_t capacity) {
+    return VirtualAlloc(NULL, sizeof(Arena) + capacity, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+}
+
+void osReserve(void *ptr) {
+}
+
+void osDecommit(void *ptr) {
+}
+
+void osFree(void *ptr) {
+}
+
+#endif