Add .gitignore and IntelliJ IDEA project configuration files and projects for cpp intro, pointers and classes

cpp/intro/main.cpp

@@ -0,0 +1,36 @@
+#include <iostream>
+#include "functions.h"
+
+using namespace std;
+
+void functionB() {}
+void functionC(); // forward declaration
+void functionD(); // forward declaration
+
+int main() {
+    std::cout << "Hello, World!" << std::endl;
+
+    // functionA(); // compiler error - functionA is defined after call
+    functionB(); // no error - functionB is defined before call
+    // functionC(); // linker error - functionC is declared but not defined
+    functionD(); // no error - functionD is declared and defined
+    functionE();
+    // functionF(); // linker error - functionF is defined twice
+
+    byte b;
+    int8_t b2;
+    short s;
+    int i;
+    long l;
+    long long ll;
+
+    cout << "size of short: " << sizeof(short) << endl;
+    cout << "size of int: " << sizeof(int) << endl;
+    cout << "size of long: " << sizeof(long) << endl;
+    cout << "size of long long: " << sizeof(long long) << endl;
+
+    return 0;
+}
+
+void functionA() {}
+void functionD() {}