move exercises and lectures into subfolders

Exercises/C21/sprintf_example.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+    int i;
+    char FileName[100];
+
+    for ( i = 1 ; i < 10 ; i++)
+    {
+        //'Print' text into string
+        sprintf(FileName , "file%d.dat" , i);
+
+        // Sidplay the name created
+        printf("Current file name: %s\n", FileName);
+    }
+
+    return 0;
+}