Add iostream and initialization

ch_1/initialization/Makefile

@@ -0,0 +1,8 @@
+all:
+	g++ main.cpp -o main -O2 -DNDEBUG -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+debug:
+	g++ main.cpp -o main -ggdb -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+clean:
+	rm -r main

ch_1/initialization/main.cpp

@@ -0,0 +1,11 @@
+#include <iostream>
+
+int main() {
+    int x { 0 };
+    double pi { 3.1415 };
+    [[maybe_unused]] double tau { 6.2830 };
+
+    std::cout << pi;
+
+    return 0;
+}

ch_1/iostream/Makefile

@@ -0,0 +1,8 @@
+all:
+	g++ main.cpp -o main -O2 -DNDEBUG -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+debug:
+	g++ main.cpp -o main -ggdb -pedantic-errors -Wall -Weffc++ -Wextra -Wconversion -Wsign-conversion -std=c++23
+
+clean:
+	rm -r main

ch_1/iostream/main.cpp

@@ -0,0 +1,16 @@
+#include <iostream>
+
+int main() {
+    std::cout << "Hello, world!\n";
+
+    double pi { 3.1415 };
+    std::cout << "pi is approximately " << pi << std::endl;
+
+    std::cout << "Enter a character: ";
+    char c { };
+    std::cin >> c;
+
+    std::cout << "You entered " << c << "\n";
+    
+    return 0;
+}