Corrected the header, added output.

example_07-01.cpp

@@ -1,12 +1,17 @@
-// alphablend <imageA> <image B> <x> <y> <width> <height> <alpha> <beta>
-//
+// Example 7-1. Using the default random number generator to generate a pair of integers
+// and a pair of floating-point numbers
+
 //#include <opencv2/opencv.hpp>
 #include <opencv2/core/core.hpp>
 #include <iostream>
 
 using namespace std;
 
 int main(int argc, char** argv) {
+  cout << "\nExample 7-1. Using the default random number generator"
+       << "\nto generate a pair of integers and a pair of"
+       << "\n floating-point numbers"
+       << "\n\nCall:\n" << argv[0] << "\n" << endl;
 
   cv::RNG rng = cv::theRNG();
   cout << "An integer: "      << (int)rng   << endl;