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diff --git a/CM2005 Object Oriented Programming/Topic 4/4.3.1/topic4.cpp b/CM2005 Object Oriented Programming/Topic 4/4.3.1/topic4.cpp
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+#include <iostream>
+#include <vector>
+#include <string>
+
+//using namespace std;
+
+int main()
+{
+  //vector<string> a;
+  std::vector<std::string> strings;
+  strings.push_back("one");
+  strings.push_back("two");
+  strings.push_back("three");
+  // we use const because we won't mutate the data in the s variable
+  // Because we're only reading, we don't want to create a copy
+  // so we use a reference '&' instead
+  for (const std::string& s:strings)
+  {
+    std::cout << s << std::endl;
+    std::string lel = "lol";
+    //s.append(lel); // we can't use this because s is of type const
+  }
+}
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