487: Highlights

• If you want to maintain state information in a status variable, then choose an integral data type of sufficient size, and then instantiate a pattern such as the following:

  unsigned char status variable name; 
  

• If you want to set a particular bit in a status variable, then combine the status variable with the corresponding power-of-2 integer using the bitwise or operator, |, and then assign the status variable to the result:

  status variable = status variable | power of 2; 
  

• If you want to test a particular bit in a status variable, then combine the status variable with the corresponding power-of-2 integer using the bitwise and operator, &, and then test the resulting value in an if statement.

  if (status variable & power of 2) 
    ... 
  

• Whenever you use the bitwise-and operator, &, you can treat one operand as a mask that lets through some bits of the other operand and that filters out others.
• If you want to test several bits in a status variable to see whether any are set, then combine the status variable with an appropriate multibit mask.