diff --git a/test_your_setup/README.md b/test_your_setup/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..719a06b9d60804e2a1f276139469279477682227
--- /dev/null
+++ b/test_your_setup/README.md
@@ -0,0 +1,30 @@
+# Compile:
+
+## hello.cc
+g++ hello.cc
+clang++ hello.cc
+
+## hello_c++20.cc
+g++ -std=c++20 hello_c++20.cc 
+clang++ -std=c++20 -stdlib=libc++ hello_c++20.cc 
+
+## hello_m.cc
+
+With gcc:
+g++ -std=c++20 -fmodules-ts -xc++-system-header iostream
+g++ -std=c++20 -fmodules-ts hello_m.cc
+
+with clang:
+clang++ -std=c++20 -stdlib=libc++ -fmodules hello_m.cc
+
+## hello_c++20_m.cc
+
+With gcc:
+g++ -std=c++20 -fmodules-ts -xc++-system-header concepts
+g++ -std=c++20 -fmodules-ts -xc++-system-header iostream
+g++ -std=c++20 -fmodules-ts hello_c++20_m.cc
+
+With clang:
+clang++ -std=c++20 -stdlib=libc++ -fmodules hello_c++20_m.cc
+
+
diff --git a/test_your_setup/hello.cc b/test_your_setup/hello.cc
new file mode 100644
index 0000000000000000000000000000000000000000..da9e571df49e6724b13114a924b7860a0c26b538
--- /dev/null
+++ b/test_your_setup/hello.cc
@@ -0,0 +1,7 @@
+#include <iostream>
+
+auto main() -> int
+{
+    std::cout << "Hello, world!\n";
+}
+
diff --git a/test_your_setup/hello_c++20.cc b/test_your_setup/hello_c++20.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5aa6763727927617c1d9dc9808dbff4998c85483
--- /dev/null
+++ b/test_your_setup/hello_c++20.cc
@@ -0,0 +1,21 @@
+#include <iostream>
+#include <concepts>
+
+auto message(auto&& x)
+{
+    std::cout << x << "\n";
+}
+
+template <class T>
+concept is_a_number = std::integral<T> or std::floating_point<T>;
+
+auto main() -> int
+{
+    message("Hello, world!");
+    auto n = 1234.0;
+    if constexpr (is_a_number<decltype(n)>)
+	std::cout << n << " is a number.\n";
+    else
+	std::cout << n << " is not a number!\n";
+}
+
diff --git a/test_your_setup/hello_c++20_m.cc b/test_your_setup/hello_c++20_m.cc
new file mode 100644
index 0000000000000000000000000000000000000000..acbf1f668f10ede246786c93ff71196481b7e515
--- /dev/null
+++ b/test_your_setup/hello_c++20_m.cc
@@ -0,0 +1,21 @@
+import <iostream>;
+import <concepts>;
+
+auto message(auto&& x)
+{
+    std::cout << x << "\n";
+}
+
+template <class T>
+concept is_a_number = std::integral<T> or std::floating_point<T>;
+
+auto main() -> int
+{
+    message("Hello, world!");
+    auto n = 1234.0;
+    if constexpr (is_a_number<decltype(n)>)
+	std::cout << n << " is a number.\n";
+    else
+	std::cout << n << " is not a number!\n";
+}
+
diff --git a/test_your_setup/hello_m.cc b/test_your_setup/hello_m.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f743015337ce7b049038e5ba97b0fca1e08ae90d
--- /dev/null
+++ b/test_your_setup/hello_m.cc
@@ -0,0 +1,7 @@
+import <iostream>;
+
+auto main() -> int
+{
+    std::cout << "Hello, world!\n";
+}
+