diff --git a/src/Module/CppLibrary/CppLibrary.hpp b/src/Module/CppLibrary/CppLibrary.hpp
new file mode 100644
index 0000000..0db4adb
--- /dev/null
+++ b/src/Module/CppLibrary/CppLibrary.hpp
@@ -0,0 +1,3 @@
+#pragma once
+
+#include "File/File.hpp"
\ No newline at end of file
diff --git a/src/Module/CppLibrary/File/File.hpp b/src/Module/CppLibrary/File/File.hpp
new file mode 100644
index 0000000..0341d74
--- /dev/null
+++ b/src/Module/CppLibrary/File/File.hpp
@@ -0,0 +1,74 @@
+#pragma once
+
+#include <cassert>
+#include <cstdint>
+#include <fstream>
+#include <limits>
+#include <vector>
+
+namespace Fig::CppLibrary
+{
+    using FileIDType = uint16_t;
+    struct File
+    {
+        FileIDType id;
+        std::fstream *fs;
+    };
+    class FileManager
+    {
+    private:
+        std::vector<File *> handlers;
+        std::vector<FileIDType> free_handlers;
+
+        FileIDType allocated = 0;
+
+    public:
+        static constexpr FileIDType MAX_HANDLERS = std::numeric_limits<FileIDType>::max();
+        static constexpr unsigned int MAX_FILE_BUF = 961200; // bytes
+
+        FileIDType AllocFile(std::fstream *fs)
+        {
+            FileIDType id = allocated++;
+            File *f = new File{.id = id, .fs = fs};
+            handlers.push_back(f);
+            return id;
+        }
+
+        void CloseFile(FileIDType id)
+        {
+            assert(id < allocated && "CloseHandler: id out of range");
+            File *f = handlers[id];
+            if (f == nullptr) { return; }
+            f->fs->close();
+            delete f->fs;
+            delete f;
+            free_handlers.push_back(id);
+            handlers[id] = nullptr;
+        }
+
+        File *GetNextFreeFile()
+        {
+            // if there is no free handler, create a new one
+            if (free_handlers.size() > 0)
+            {
+                FileIDType id = *free_handlers.begin();
+                handlers[id] = new File{.id = id, .fs = new std::fstream};
+                free_handlers.erase(free_handlers.begin());
+                return handlers[id];
+            }
+            return handlers[AllocFile(new std::fstream)];
+        }
+
+        File *GetFile(FileIDType id)
+        {
+            assert(id < allocated && "GetFile: id out of range");
+            return handlers[id];
+        }
+
+        static FileManager &getInstance()
+        {
+            static FileManager fm;
+            return fm;
+        }
+    };
+}; // namespace Fig::CppLibrary
\ No newline at end of file
diff --git a/src/Module/Library/std/file/file.fig b/src/Module/Library/std/file/file.fig
new file mode 100644
index 0000000..fffdb94
--- /dev/null
+++ b/src/Module/Library/std/file/file.fig
@@ -0,0 +1,101 @@
+/*
+    Official Module `std.file`
+    Library/std/file/file.fig
+
+    Copyright © 2026 PuqiAR. All rights reserved.
+*/
+
+import _builtins;
+import std.io;
+
+
+public struct __OpenMode
+{
+    public App: Int = 1;
+    public Ate: Int = 2;
+    public Bin: Int = 4;
+    public In: Int = 8;
+    public Out: Int = 16;
+    public Trunc: Int = 32;
+
+    public __openmode_to_string: Map = 
+    {
+        1 : "App",
+        2 : "Ate",
+        4 : "Bin",
+        8 : "In",
+        16 : "Out",
+        32 : "Trunc"
+    };
+}
+public const OpenMode := new __OpenMode{};
+
+public func repr_mode(mode: Int) -> String
+{
+    return OpenMode.__openmode_to_string[mode];
+}
+
+
+
+public struct FileError
+{
+    msg: String;
+}
+
+impl Error for FileError
+{
+    getErrorClass()
+    {
+        return "FileError";
+    }
+    getErrorMessage()
+    {
+        return msg;
+    }
+    toString()
+    {
+        return getErrorClass() + ": " + msg;
+    }
+}
+
+public struct File
+{
+    path: String;
+    mode: Int;
+
+    id: Int;
+
+    public func read() -> Any
+    {
+        return __fstdfile_read(id);
+    }
+
+    public func write(object: String) -> Null
+    {
+        __fstdfile_write(id, object);
+    }
+
+    public func close() -> Null
+    {
+        __fstdfile_close(id);
+    }
+
+    public func getID() -> Int
+    {
+        return id;
+    }
+}
+
+public func open(path: String, mode: Int) 
+{
+    const id := __fstdfile_open(path, mode);
+    if not __fstdfile_is_open(id)
+    {
+        throw new FileError{"File " + path + " open failed"};
+    }
+    return new File{
+        path: path,
+        mode: mode,
+        id: id
+    };
+}
\ No newline at end of file
diff --git a/src/Module/builtins.cpp b/src/Module/builtins.cpp
index 6e6dbb6..0582d68 100644
--- a/src/Module/builtins.cpp
+++ b/src/Module/builtins.cpp
@@ -5,13 +5,19 @@
 #include <Ast/Statements/ControlSt.hpp>
 #include <Ast/astBase.hpp>
 #include <Ast/functionParameters.hpp>
-#include <Evaluator/Context/context.hpp>
-#include <Core/fig_string.hpp>
 #include <Ast/AccessModifier.hpp>
+
 #include <Evaluator/Value/structType.hpp>
 #include <Evaluator/Value/value.hpp>
-#include <Module/builtins.hpp>
+#include <Evaluator/Value/Type.hpp>
+#include <Evaluator/Context/context.hpp>
 
+#include <Module/CppLibrary/CppLibrary.hpp>
+
+#include <Module/builtins.hpp>
+#include <Core/fig_string.hpp>
+
+#include <cassert>
 #include <memory>
 #include <print>
 #include <iostream>
@@ -132,9 +138,18 @@ namespace Fig::Builtins
             {u8"__fmath_tan", 1},
             {u8"__fmath_tanh", 1},
             {u8"__fmath_trunc", 1},
+
+            /* file start */
+            {u8"__fstdfile_open", 2},
+            {u8"__fstdfile_close", 1},
+            {u8"__fstdfile_is_open", 1},
+
+            {u8"__fstdfile_read", 1},
+            {u8"__fstdfile_write", 2},
         };
         return builtinFunctionArgCounts;
     }
+
     const std::unordered_map<FString, BuiltinFunction> &getBuiltinFunctions()
     {
         static const std::unordered_map<FString, BuiltinFunction> builtinFunctions{
@@ -421,6 +436,47 @@ namespace Fig::Builtins
                  ValueType::DoubleClass d = val->getNumericValue();
                  return std::make_shared<Object>(trunc(d));
              }},
+            /* file start */
+            {u8"__fstdfile_open",
+             [](const std::vector<ObjectPtr> &args) -> ObjectPtr {
+                 const FString &path = args[0]->as<ValueType::StringClass>();
+                 const ValueType::IntClass &mode = args[1]->as<ValueType::IntClass>();
+
+                 CppLibrary::File *f = CppLibrary::FileManager::getInstance().GetNextFreeFile();
+                 f->fs->open(path.toBasicString(), static_cast<unsigned int>(mode));
+                 return std::make_shared<Object>(static_cast<ValueType::IntClass>(f->id));
+             }},
+            {u8"__fstdfile_close",
+             [](const std::vector<ObjectPtr> &args) -> ObjectPtr {
+                 const ValueType::IntClass &id = args[0]->as<ValueType::IntClass>();
+                 CppLibrary::FileManager::getInstance().CloseFile(id);
+                 return Object::getNullInstance();
+             }},
+            {u8"__fstdfile_is_open",
+             [](const std::vector<ObjectPtr> &args) -> ObjectPtr {
+                 const ValueType::IntClass &id = args[0]->as<ValueType::IntClass>();
+                 return std::make_shared<Object>(CppLibrary::FileManager::getInstance().GetFile(id)->fs->is_open());
+             }},
+            {u8"__fstdfile_read",
+             [](const std::vector<ObjectPtr> &args) -> ObjectPtr {
+                 const ValueType::IntClass &id = args[0]->as<ValueType::IntClass>();
+                 CppLibrary::File *f = CppLibrary::FileManager::getInstance().GetFile(id);
+
+                 char *buf = new char[CppLibrary::FileManager::MAX_FILE_BUF];
+                 f->fs->read(buf, CppLibrary::FileManager::MAX_FILE_BUF);
+                 return std::make_shared<Object>(ValueType::StringClass(reinterpret_cast<const char8_t *>(buf)));
+             }},
+            {u8"__fstdfile_write",
+             [](const std::vector<ObjectPtr> &args) -> ObjectPtr {
+                 const ValueType::IntClass &id = args[0]->as<ValueType::IntClass>();
+                 const ValueType::StringClass &str = args[1]->as<ValueType::StringClass>();
+
+                 CppLibrary::File *f = CppLibrary::FileManager::getInstance().GetFile(id);
+                 const char *data = reinterpret_cast<const char *>(str.c_str());
+                 f->fs->write(data, str.size());
+                 return std::make_shared<Object>(static_cast<ValueType::IntClass>(str.length()));
+                 // bytes wrote
+             }},
         };
         return builtinFunctions;
     }
diff --git a/src/Module/builtins.hpp b/src/Module/builtins.hpp
index 86b3d26..7e9da06 100644
--- a/src/Module/builtins.hpp
+++ b/src/Module/builtins.hpp
@@ -10,6 +10,7 @@
 #include <unordered_map>
 #include <functional>
 #include <vector>
+#include <fstream>
 
 namespace Fig
 {
@@ -44,7 +45,20 @@ namespace Fig
         using BuiltinFunction = std::function<ObjectPtr(const std::vector<ObjectPtr> &)>;
 
         const std::unordered_map<FString, int> &getBuiltinFunctionArgCounts();
-        const std::unordered_map<FString, BuiltinFunction> &getBuiltinFunctions();
+
+        /*
+            File
+        */
+
+        struct FileHandler
+        {
+            int64_t id;
+            std::fstream *fs;
+        };
+
+        std::vector<FileHandler *> &getFileHandlers(); // global
+
+        const std::unordered_map<FString, BuiltinFunction> &getBuiltinFunctions();        
 
         inline bool isBuiltinFunction(const FString &name)
         {