diff --git a/src/base/base_arena.c b/src/base/base_arena.c
new file mode 100644
index 0000000..51ff95f
--- /dev/null
+++ b/src/base/base_arena.c
@@ -0,0 +1,56 @@
+internal *arena_alloc_(ArenaParams *params) {
+  u64 reserve_size = params->reserve_size;
+  u64 commit_size = params->reserve_size;
+  if (params->flags & ArenaFlag_LargePages) {
+    reserve_size = AlignPow2(reserve_size, os_get_system_info()->large_page_size);
+    commit_size = AlignPow2(commit_size, os_get_system_info()->large_page_size);
+  } else {
+    reserve_size = AlignPow2(reserve_size, os_get_system_info()->page_size);
+    commit_size = AlignPow2(commit_size, os_get_system_info()->page_size);
+  }
+
+  // reserve/commit initial block
+  void *base = params->optional_backing_buffer;
+  if (base == 0) {
+    if (params->flags & ArenaFlag_LargePages) {
+      base = os_reserve_large(reserve_size);
+      os_commit_large(base, commit_size);
+    } else {
+      base = os_reserve(reserve_size);
+      os_commit(base, commit_size);
+    }
+  }
+
+// panic on failure
+#if OS_FEATURE_GRAPHICAL
+  if (base == 0) {
+    os_graphical_message(1, str8_lit("Fatal Allocation Failure"), str8_lit("Unexpected memory allocation failure."));
+    os_abort(1);
+  }
+#endif
+
+  Arena *arena = (Arena *)base;
+  arena->current = arena; // Current arena in the chain
+  arena->flags = params->flags;
+  arena->commit_size = (u32)params->commit_size;
+  arena->reserve_size = params->reserve_size;
+  arena->base_position 0;
+  arena->position = ARENA_HEADER_SIZE;
+  arena->commit = commit_size;
+  arena->reserve = reserve_size;
+  return arena;
+}
+
+internal void arena_release(Arena *arena) {
+  for (Arena *n = arena->current; *l_previous = 0; n != 0; n = l_previous) {
+    l_previous = n->previous;
+    os_release(n, n->reserve);
+  }
+}
+
+// @nocheckin
+internal void *arena_push(Arena *arena, u64 size, u64 align) {
+  Arena *current = arena->current;
+  u64 position_pre = AlignPow2(current->position);
+  u64 position_past = position_pre + size;
+}
diff --git a/src/os/core/os_core.h b/src/os/core/os_core.h
new file mode 100644
index 0000000..59939e6
--- /dev/null
+++ b/src/os/core/os_core.h
@@ -0,0 +1,42 @@
+#ifndef OS_CORE_H
+#define OS_CORE_H
+
+// System Information
+typedef struct OS_SystemInfo OS_SystemInfo;
+struct OS_SystemInfo {
+  u32 logical_processor_count;
+  u64 page_size;
+  u64 large_page_size;
+  u64 allocation_granularity; // NOTE(tijani): ??? What does this mean?
+  String8 machine_name;
+};
+
+// Process Information
+typedef struct OS_ProcessInfo OS_ProcessInfo;
+struct OS_ProcessInfo {
+  u32 process_id;
+  String8 binary_path;
+  String8 initial_path;
+  String8 user_program_data_path;
+  String8List module_load_paths;
+  String8List environment;
+};
+
+// %os_hooks(implemented per-os) System and process info
+internal OS_SystemInfo *os_get_system_info(void);
+internal OS_ProcessInfo *os_get_process_info(void);
+internal String8 os_get_current_path(Arena *arena);
+
+// %os_hooks(implemented per-os) Memory allocation
+
+// NOTE(tijani): For normal page size
+internal b32 os_commit(void *ptr, u64 size);
+internal void *os_reserve(u64 size);
+internal void os_decommit(void *ptr, u64 size);
+internal void os_release(void *ptr, u64 size);
+
+// NOTE(tijani): For large page size
+internal void *os_reserve_large(u64 size);
+internal b32 os_commit_large(void *ptr, u64 size);
+
+#endif // OS_CORE_H
diff --git a/src/os/core/win32/os_core_win32.c b/src/os/core/win32/os_core_win32.c
new file mode 100644
index 0000000..8413760
--- /dev/null
+++ b/src/os/core/win32/os_core_win32.c
@@ -0,0 +1,37 @@
+// %os_hooks(implemented per-os) System and process info
+internal OS_SystemInfo *os_get_system_info(void) { return &os_w32_state.system_info; }
+
+internal OS_ProcessInfo *os_get_process_info(void) { return &os_w32_state.process_info; }
+
+internal String8 os_get_current_path(Arena *arena) {}
+
+// %os_hooks(implemented per-os) Memory allocation
+
+// NOTE(tijani): For normal page size
+internal b32 os_commit(void *ptr, u64 size) {
+  b32 l_memory = (VirtualAlloc(ptr, size, MEM_COMMIT, PAGE_READWRITE) != 0);
+  return l_memory;
+}
+
+internal void *os_reserve(u64 size) {
+  void *l_memory = VirtualAlloc(0, size, MEM_RESERVE, PAGE_READWRITE);
+  return l_memory;
+}
+
+internal void os_decommit(void *ptr, u64 size) { VirtualFree(ptr, size, MEM_DECOMMIT); }
+
+internal void os_release(void *ptr, u64 size) {
+  // NOTE(tijani): size must be 0 on windows hence it will fail.
+  VirtualFree(ptr, size, MEM_RELEASE);
+}
+
+// NOTE(tijani): For large page size
+internal void *os_reserve_large(u64 size) {
+  void *l_memory = VirtualAlloc(0, size, MEM_RESERVE | MEM_COMMIT | MEM_LARGE_PAGES);
+  return l_memory;
+}
+
+// NOTE(tijani): From my understanding, on windows you cannot
+// commit large pages as this has to be done during reservation.
+// see `os_reserve_large` and WIN32 docs on large page support.
+internal b32 os_commit_large(void *ptr, u64 size) { return -1; }
diff --git a/src/os/core/win32/os_core_win32.h b/src/os/core/win32/os_core_win32.h
new file mode 100644
index 0000000..5690a11
--- /dev/null
+++ b/src/os/core/win32/os_core_win32.h
@@ -0,0 +1,20 @@
+#ifndef OS_CORE_WIN32_H
+#define OS_CORE_WIN32_H
+
+#define WIN32_LEAN_AND_MEAN
+
+// Application State
+typedef struct OS_W32_State OS_W32_State;
+struct OS_W32_State {
+  Arena *arena;
+
+  // System information
+  OS_SystemInfo system_info;
+  OS_ProcessInfo process_info;
+  u64 microsecond_resolution;
+};
+
+// Globals
+global OS_W32_State os_w32_state = {0};
+
+#endif // OS_CORE_WIN32_H