From 4ffe05c74b078675019cdce97add647553dd6701 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=B9i=20Th=E1=BA=BF=20Vinh?=
 <93034845+thevinh23@users.noreply.github.com>
Date: Sun, 19 Apr 2026 20:51:29 +0700
Subject: [PATCH 1/2] Added sub-items for 'File Input and Output'

Added sub-items for 'File Input and Output' section in sidebar.
---
 wiki/cpp-tutorial/sidebar.ts | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/wiki/cpp-tutorial/sidebar.ts b/wiki/cpp-tutorial/sidebar.ts
index 019b2e4..6b40175 100644
--- a/wiki/cpp-tutorial/sidebar.ts
+++ b/wiki/cpp-tutorial/sidebar.ts
@@ -134,7 +134,25 @@ const sidebar = [
                 ],
                 collapsed: true,
             },
-            { text: "File Input and Output", link: "/cpp-tutorial/file-io" },
+            { 
+                text: "File Input and Output", 
+                link: "/cpp-tutorial/file-io",
+                items: [
+                    {
+                        text: "Read a File",
+                        link: "/cpp-tutorial/file-io#read-a-file",
+                    },
+                    {
+                        text: "Write a File",
+                        link: "/cpp-tutorial/file-io#write-a-file",
+                    },
+                    {
+                        text: "Redirecting standard input/output",
+                        link: "/cpp-tutorial/file-io#redirecting-stdio",
+                    },
+                ],
+                collapsed: true;
+            },
             {
                 text: "User Defined Types",
                 link: "/cpp-tutorial/user-defined-types",

From dfa62e9a44876a17173f91faa81f7372d012110c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=B9i=20Th=E1=BA=BF=20Vinh?=
 <93034845+thevinh23@users.noreply.github.com>
Date: Sun, 19 Apr 2026 16:14:27 +0000
Subject: [PATCH 2/2] Added 'File Input and Output' documentation

---
 wiki/cpp-tutorial/file-io.md | 63 ++++++++++++++++++++++++++++++++++++
 wiki/cpp-tutorial/sidebar.ts |  2 +-
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/wiki/cpp-tutorial/file-io.md b/wiki/cpp-tutorial/file-io.md
index dae69fc..07115a1 100644
--- a/wiki/cpp-tutorial/file-io.md
+++ b/wiki/cpp-tutorial/file-io.md
@@ -1,3 +1,66 @@
 ---
 wip: true
 ---
+
+# File Input and Output
+In C++, you can use the `fstream` library to create, write and read files. \
+To use fstream, you need to include the `<iostream>` **AND** `<fstream>` header files.
+
+``` cpp
+#include <iostream>
+#include <fstream> 
+```
+The `<fstream>` library provides three main classes:
+|Function|Description|
+|--------|-----------|
+|`std::ofstream`|Used to create and write to files|
+|`std::ifstream`|Used to read from files|
+|`std::fstream`|Used for both reading and writing|
+
+::: info Note
+`std::fstream` is a general-purpose file stream, while `std::ifstream` and `std::ofstream` are more specific and commonly used in practice.
+:::
+
+## Read a File (`std::ifstream`) {#read-a-file}
+`std::ifstream` is used to read data from a file.
+
+``` cpp
+std::string line;
+
+std::ifstream file("filename.txt");
+
+if (!file) return 1;
+
+while (std::getline(file, line)) {
+    std::cout << line << "\n";
+}
+
+file.close();
+```
+
+Using a `while` loop with `getline()` allows us to read a file line by line until we reach the end, and then print each line.
+
+## Write a File (`std::ofstream`) {#write-a-file}
+`std::ofstream` is used to write data to a file.
+
+``` cpp
+std::ofstream file("filename.txt");
+
+if (!file) return 1;
+
+file << "Hello Together C & C++!";
+
+file.close();
+```
+This will create the file if it doesn’t exist, or overwrite it if it already exists.
+
+## Redirecting standard input/output {#redirecting-stdio}
+`freopen` is used to redirect standard input and output streams to files.\
+It reassigns `stdin` or `stdout` to a file instead of the default console input/output.
+``` cpp
+freopen("input.txt", "r", stdin);
+freopen("output.txt", "w", stdout);
+```
+::: info Note
+`freopen` is commonly used in competitive programming for convenience, but it is not recommended for general C++ applications.
+:::
\ No newline at end of file
diff --git a/wiki/cpp-tutorial/sidebar.ts b/wiki/cpp-tutorial/sidebar.ts
index 6b40175..3feda6b 100644
--- a/wiki/cpp-tutorial/sidebar.ts
+++ b/wiki/cpp-tutorial/sidebar.ts
@@ -151,7 +151,7 @@ const sidebar = [
                         link: "/cpp-tutorial/file-io#redirecting-stdio",
                     },
                 ],
-                collapsed: true;
+                collapsed: true,
             },
             {
                 text: "User Defined Types",