Buffers

• A buffer is a portion of memory set aside to store data, often before it is sent to an external device or as it is received from an external device
• Buffers are common to many kinds of systems including mechanical ones.
  • Film projectors tend to pull the film at a variable rate, so a loop of extra film is made between the feed and takeup reels.
  • A water tank on the top of an apartment building acts as a buffer for water use in the building

• Fully buffered: data is moved only when the buffer is full
• Line buffered: the buffer is a line (e.g., sequence of chars terminated with a new line
• Unbuffered: no buffering

For buffered output, the information is queued up in the buffer until it is full and then written.