diff --git a/demos/comma.cpp b/demos/comma.cpp
new file mode 100644
index 0000000..4ad62c8
--- /dev/null
+++ b/demos/comma.cpp
@@ -0,0 +1,17 @@
+#include <iostream>
+using std::cin;
+using std::cout;
+using std::endl;
+
+int main() {
+    std::string s;
+
+    while (cin >> s, s.length() > 5) {
+        cout << s << " is longer than 5\n";
+    }
+    cout << s << " is too short\n";
+
+    for (int i = 0, j = 0; i != 5; ++i, ++j) {
+        cout << i << ", " << j << endl;
+    }
+}
diff --git a/demos/file_io_example.cpp b/demos/file_io_example.cpp
new file mode 100644
index 0000000..5399738
--- /dev/null
+++ b/demos/file_io_example.cpp
@@ -0,0 +1,24 @@
+#include <fstream>
+#include <iomanip>
+#include <iostream>
+#include <string>
+
+void print_bytes(std::string infile) {
+    std::ifstream in{infile};
+
+    int c;
+    while ((c = in.get()) != EOF) {
+        std::cout << "read: " << std::setw(3) << c << " [" << char(c) << "]"
+                  << std::endl;
+    }
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        std::cout << "Usage: " << argv[0] << " filename" << std::endl;
+        return 1;
+    }
+
+    print_bytes(argv[1]);
+    return 0;
+}
diff --git a/demos/map_and_set.cpp b/demos/map_and_set.cpp
new file mode 100644
index 0000000..c1377df
--- /dev/null
+++ b/demos/map_and_set.cpp
@@ -0,0 +1,123 @@
+#include <iostream>
+using std::cin;
+using std::cout;
+using std::endl;
+#include <map>
+#include <set>
+
+void test_map() {
+    std::map<std::string, int> msi;
+
+    msi.insert(std::make_pair("Kalle", 1));
+    msi.emplace("Lisa", 2);
+    msi["Kim"] = 3;
+
+    for (const auto &a : msi) {
+        cout << a.first << " : " << a.second << endl;
+    }
+
+    cout << "Kim --> " << msi.at("Kim") << endl;
+    cout << "Lisa --> " << msi["Lisa"] << endl;
+    cout << "Hans --> " << msi["Hans"]
+         << endl; // [] default-konstruerar ett värde
+                  // för nycklar som inte finns
+    try {
+        cout << "Nisse --> " << msi.at("Nisse") << endl;
+    } catch (std::out_of_range &e) {
+        cout << "Nisse not found: " << e.what() << endl;
+    }
+    const auto &kim = msi.find("Kim");
+    if (kim != msi.end()) {
+        cout << "Kim : " << kim->second << endl;
+    } else {
+        cout << "Kim not found\n";
+    }
+    auto nisse = msi.find("Nisse");
+    if (nisse != msi.end()) {
+        cout << "Nisse : " << nisse->second << endl;
+    } else {
+        cout << "Nisse not found\n";
+    }
+}
+
+void test_set() {
+    std::set<int> ints{1, 3, 7};
+
+    ints.insert(5);
+
+    for (auto x : ints) {
+        cout << x << " ";
+    }
+    cout << endl;
+
+    auto has_one = ints.find(1);
+
+    if (has_one != ints.end()) {
+        cout << "one is in the set\n";
+    } else {
+        cout << "one is not in the set\n";
+    }
+
+    if (ints.count(1)) {
+        cout << "one is in the set\n";
+    } else {
+        cout << "one is not in the set\n";
+    }
+
+    auto has_two = ints.find(2);
+
+    if (has_two != ints.end()) {
+        cout << "two is in the set\n";
+    } else {
+        cout << "two is not in the set\n";
+    }
+
+    if (ints.count(2)) {
+        cout << "two is in the set\n";
+    } else {
+        cout << "two is not in the set\n";
+    }
+
+    auto has_five = ints.find(5);
+
+    if (has_five != ints.end()) {
+        cout << "five is in the set\n";
+    } else {
+        cout << "five is not in the set\n";
+    }
+
+    ints.erase(5);
+
+    auto has_five_now = ints.find(5);
+
+    if (has_five_now != ints.end()) {
+        cout << "five is in the set\n";
+    } else {
+        cout << "five is not in the set\n";
+    }
+}
+
+void test_set_bounds() {
+    std::set<int> ints{9, 1, 3, 7, 5};
+
+    auto lb3 = ints.lower_bound(3);
+    cout << "lb3: " << *lb3 << endl;
+    auto ub3 = ints.upper_bound(3);
+    cout << "ub3: " << *ub3 << endl;
+    auto lb4 = ints.lower_bound(4);
+    cout << "lb4: " << *lb4 << endl;
+    auto ub4 = ints.upper_bound(4);
+    cout << "ub4: " << *ub4 << endl;
+    auto er = ints.equal_range(7);
+    if (er.first == er.second) {
+        cout << "er.first == er.second";
+    }
+    cout << ", er.first: " << *er.first << ", er.second: " << *er.second
+         << endl;
+}
+
+int main() {
+    test_map();
+    test_set();
+    test_set_bounds();
+}
diff --git a/demos/print_seq.h b/demos/print_seq.h
new file mode 100644
index 0000000..c26ad6f
--- /dev/null
+++ b/demos/print_seq.h
@@ -0,0 +1,14 @@
+#ifndef PRINT_SEQ_H
+#define PRINT_SEQ_H
+
+#include <iostream>
+
+template <typename C> void print_seq(const C &c) {
+    using std::cout;
+    using std::endl;
+
+    cout << "[length: " << c.size() << "] ";
+    for (const auto &x : c) std::cout << x << " ";
+    cout << endl;
+}
+#endif
diff --git a/demos/typecast_int_float.cpp b/demos/typecast_int_float.cpp
new file mode 100644
index 0000000..7de2f84
--- /dev/null
+++ b/demos/typecast_int_float.cpp
@@ -0,0 +1,15 @@
+#include <iostream>
+
+int main() {
+    int a{1234};
+    float f{1234.0};
+
+    std::cout << "sizeof(int): " << sizeof(int)
+              << ", sizeof(float): " << sizeof(float) << std::endl;
+
+    std::cout << "static_cast: " << static_cast<float>(a) << " "
+              << static_cast<int>(f) << std::endl;
+
+    std::cout << "reinterpret_cast: " << *reinterpret_cast<float *>(&a) << " "
+              << *reinterpret_cast<int *>(&f) << std::endl;
+}