/**
  \example sdcard2.cpp 

  This sketch performs block reads and writes to an SD card and
  measures how long it takes.

  For this sample output, I started with a 4GB PNY SDHC card and later
  switched to a 4GB SanDisk SDHC card:
  \code
  b
  Ln 23.463 Read 225 blocks at 114.97KB/sec
  Ln 25.484 Wrote 129 blocks at 65.85KB/sec
  b
  Ln 135.113 Read 250 blocks at 127.62KB/sec
  Ln 137.118 Wrote 363 blocks at 185.49KB/sec
  \endcode

  Note that this sketch will \e write \e garbage into hundreds of
  blocks of your SD card, without regard for any file system that
  might be present!  Do not run this sketch on a formatted card unless
  you no longer care about its contents!
 */
