diff --git a/xeus-cpp/02_persistence.ipynb b/xeus-cpp/02_persistence.ipynb
index a208477..dd7c66e 100644
--- a/xeus-cpp/02_persistence.ipynb
+++ b/xeus-cpp/02_persistence.ipynb
@@ -69,6 +69,7 @@
   },
   {
    "cell_type": "code",
+   "execution_count": 4,
    "execution_count": 3,
    "id": "d2c38c70-3e92-446a-8c10-1c62edf177e1",
    "metadata": {},
@@ -77,6 +78,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
+      "Current Value: 2\n"
       "Current Value: 1\n"
      ]
     }
@@ -84,6 +86,14 @@
    "source": [
     "inc(); //Run this cell multiple times to see persistence in action"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "e4068173-ab1b-44e5-b439-a4063adfaa67",
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
@@ -97,6 +107,7 @@
    "file_extension": ".cpp",
    "mimetype": "text/x-c++src",
    "name": "C++",
+   "version": "23"
    "nbconvert_exporter": "",
    "pygments_lexer": "",
    "version": "cxx23"
diff --git a/xeus-cpp/06_cpp_oop.ipynb b/xeus-cpp/06_cpp_oop.ipynb
index 92d373c..e6acf72 100644
--- a/xeus-cpp/06_cpp_oop.ipynb
+++ b/xeus-cpp/06_cpp_oop.ipynb
@@ -286,6 +286,7 @@
    "file_extension": ".cpp",
    "mimetype": "text/x-c++src",
    "name": "C++",
+   "version": "17"
    "nbconvert_exporter": "",
    "pygments_lexer": "",
    "version": "cxx17"
diff --git a/xeus-cpp/07_stl_modern_cpp.ipynb b/xeus-cpp/07_stl_modern_cpp.ipynb
index 62c51b0..3e032ef 100644
--- a/xeus-cpp/07_stl_modern_cpp.ipynb
+++ b/xeus-cpp/07_stl_modern_cpp.ipynb
@@ -41,6 +41,8 @@
     "#include <optional>\n",
     "#include <variant>\n",
     "#include <functional>\n",
+    "#include <sstream>\n",
+    "using namespace std;"
     "#include <sstream>"
    ]
   },
@@ -69,6 +71,21 @@
     }
    ],
    "source": [
+    "vector<int> v = {5, 2, 8, 1, 9, 3, 7, 4, 6};\n",
+    "\n",
+    "// Sort and display\n",
+    "sort(v.begin(), v.end());\n",
+    "cout << \"Sorted: \";\n",
+    "for (int x : v) cout << x << \" \";\n",
+    "cout << endl;\n",
+    "\n",
+    "// Accumulate\n",
+    "int sum = accumulate(v.begin(), v.end(), 0);\n",
+    "cout << \"Sum: \" << sum << \"  Average: \" << (double)sum / v.size() << endl;\n",
+    "\n",
+    "// Find\n",
+    "auto it = find(v.begin(), v.end(), 7);\n",
+    "cout << \"Found 7 at index: \" << distance(v.begin(), it) << endl;"
     "std::vector<int> v = {5, 2, 8, 1, 9, 3, 7, 4, 6};\n",
     "\n",
     "// Sort and display\n",
@@ -102,6 +119,11 @@
    ],
    "source": [
     "// Transform: square each element\n",
+    "vector<int> squares(v.size());\n",
+    "transform(v.begin(), v.end(), squares.begin(), [](int x) { return x * x; });\n",
+    "cout << \"Squares: \";\n",
+    "for (int x : squares) cout << x << \" \";\n",
+    "cout << endl;"
     "std::vector<int> squares(v.size());\n",
     "std::transform(v.begin(), v.end(), squares.begin(), [](int x) { return x * x; });\n",
     "std::cout << \"Squares: \";\n",
@@ -141,6 +163,16 @@
    ],
    "source": [
     "// Word frequency counter\n",
+    "string text = \"the quick brown fox jumps over the lazy dog\";\n",
+    "map<string, int> freq;\n",
+    "\n",
+    "string word;\n",
+    "stringstream ss(text);\n",
+    "while (ss >> word) freq[word]++;\n",
+    "\n",
+    "cout << \"Word frequencies (alphabetical):\" << endl;\n",
+    "for (const auto& [w, cnt] : freq) {\n",
+    "    cout << \"  \" << w << \": \" << cnt << endl;\n",
     "std::string text = \"the quick brown fox jumps over the lazy dog\";\n",
     "std::map<std::string, int> freq;\n",
     "\n",
@@ -171,6 +203,14 @@
    ],
    "source": [
     "// Set: unique sorted elements\n",
+    "vector<int> dupes = {3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5};\n",
+    "set<int> unique_set(dupes.begin(), dupes.end());\n",
+    "\n",
+    "cout << \"Original (\" << dupes.size() << \" elements): \";\n",
+    "for (int x : dupes) cout << x << \" \";\n",
+    "cout << \"\\nUnique (\" << unique_set.size() << \" elements): \";\n",
+    "for (int x : unique_set) cout << x << \" \";\n",
+    "cout << endl;"
     "std::vector<int> dupes = {3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5};\n",
     "std::set<int> unique_set(dupes.begin(), dupes.end());\n",
     "\n",
@@ -211,6 +251,17 @@
     "auto isAbove = [threshold](int x) { return x > threshold; };  // capture by value\n",
     "auto addTo   = [&threshold](int x) { return x + threshold; };  // capture by reference\n",
     "\n",
+    "vector<int> nums = {1, 3, 5, 7, 9, 2, 4, 6, 8};\n",
+    "vector<int> above, shifted;\n",
+    "\n",
+    "copy_if(nums.begin(), nums.end(), back_inserter(above), isAbove);\n",
+    "transform(nums.begin(), nums.end(), back_inserter(shifted), addTo);\n",
+    "\n",
+    "cout << \"Above \" << threshold << \": \";\n",
+    "for (int x : above) cout << x << \" \";\n",
+    "cout << \"\\nShifted +\" << threshold << \": \";\n",
+    "for (int x : shifted) cout << x << \" \";\n",
+    "cout << endl;\n",
     "std::vector<int> nums = {1, 3, 5, 7, 9, 2, 4, 6, 8};\n",
     "std::vector<int> above, shifted;\n",
     "\n",
@@ -253,6 +304,12 @@
    "source": [
     "// unique_ptr — single ownership\n",
     "{\n",
+    "    auto uptr = make_unique<string>(\"unique owner\");\n",
+    "    cout << \"unique_ptr: \" << *uptr << endl;\n",
+    "    // auto uptr2 = uptr;  // ERROR: cannot copy unique_ptr\n",
+    "    auto uptr2 = move(uptr);  // Transfer ownership\n",
+    "    cout << \"After move, uptr is \" << (uptr ? \"valid\" : \"null\") << endl;\n",
+    "    cout << \"uptr2: \" << *uptr2 << endl;\n",
     "    auto uptr = std::make_unique<std::string>(\"unique owner\");\n",
     "    std::cout << \"unique_ptr: \" << *uptr << std::endl;\n",
     "    // auto uptr2 = uptr;  // ERROR: cannot copy unique_ptr\n",
@@ -263,6 +320,9 @@
     "\n",
     "// shared_ptr — shared ownership\n",
     "{\n",
+    "    auto sptr1 = make_shared<int>(42);\n",
+    "    auto sptr2 = sptr1;  // Both share ownership\n",
+    "    cout << \"shared value: \" << *sptr1 << \"  use_count: \" << sptr1.use_count() << endl;\n",
     "    auto sptr1 = std::make_shared<int>(42);\n",
     "    auto sptr2 = sptr1;  // Both share ownership\n",
     "    std::cout << \"shared value: \" << *sptr1 << \"  use_count: \" << sptr1.use_count() << std::endl;\n",
@@ -294,6 +354,8 @@
    ],
    "source": [
     "// std::optional\n",
+    "optional<int> safeDivide(int a, int b) {\n",
+    "    if (b == 0) return nullopt;\n",
     "std::optional<int> safeDivide(int a, int b) {\n",
     "    if (b == 0) return std::nullopt;\n",
     "    return a / b;\n",
@@ -302,12 +364,28 @@
     "auto r1 = safeDivide(10, 2);\n",
     "auto r2 = safeDivide(10, 0);\n",
     "\n",
+    "cout << \"10/2 = \" << (r1 ? to_string(*r1) : \"undefined\") << endl;\n",
+    "cout << \"10/0 = \" << (r2 ? to_string(*r2) : \"undefined\") << endl;"
     "std::cout << \"10/2 = \" << (r1 ? std::to_string(*r1) : \"undefined\") << std::endl;\n",
     "std::cout << \"10/0 = \" << (r2 ? std::to_string(*r2) : \"undefined\") << std::endl;"
    ]
   },
   {
    "cell_type": "code",
+   "execution_count": null,
+   "id": "variant-demo",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "// std::variant\n",
+    "using Number = variant<int, double, string>;\n",
+    "\n",
+    "vector<Number> numbers = {42, 3.14, string(\"forty-two\"), 100, 2.718};\n",
+    "\n",
+    "for (const auto& n : numbers) {\n",
+    "    visit([](const auto& val) {\n",
+    "        cout << val << \" (\" << typeid(val).name() << \")\" << endl;\n",
+    "    }, n);\n",
    "execution_count": 9,
    "id": "variant-demo",
    "metadata": {},
@@ -353,6 +431,9 @@
  ],
  "metadata": {
   "kernelspec": {
+   "display_name": "C++17",
+   "language": "cpp",
+   "name": "xcpp17"
    "display_name": "C++23",
    "language": "cpp",
    "name": "xcpp23"
@@ -362,6 +443,7 @@
    "file_extension": ".cpp",
    "mimetype": "text/x-c++src",
    "name": "C++",
+   "version": "17"
    "nbconvert_exporter": "",
    "pygments_lexer": "",
    "version": "cxx23"