add class_basics example

Chapter05/class_basics.cpp

@@ -0,0 +1,37 @@
+#include <cstdint> 
+#include <cstdio>
+
+class uart { 
+
+public: 
+
+    uart(std::uint32_t baud = 9600): baudrate_(baud) {
+        printf("%s\n", __func__);
+    } 
+
+    void init() { 
+        printf("%s\n", __func__);
+        write_brr(calculate_uartdiv()); 
+    } 
+
+private: 
+
+    std::uint32_t baudrate_; 
+    std::uint8_t calculate_uartdiv() { 
+        printf("%s\n", __func__);
+        return baudrate_ / 32000; 
+    } 
+
+    void write_brr(std::uint8_t) {} 
+}; 
+
+ 
+
+int main () { 
+
+    uart uart1(115200); 
+    uart1.init(); 
+
+    return 0; 
+
+}