Data & Files
CIS241

Basics of Data Access ::
  1. Storage & Retrieval (Writing & Reading)
  2. Internal/External

Internal Storage ::
  1. Direct :: assignment to named memory location
	- variable
	- property value
  2. Indirect :: passed as value of parameter, or
		returned as value of function call

Internal Retrieval ::
  1. Reference to named memory location
	- variable
	- property value
	- parameter
  2. Function call

Internal to External Data Flow ::
  1. Data written to screen
  2. Data sent to other output devices, e.g., speakers
  3. Data written to disk (hard drive, floppy, etc.)

External to Internal Data Flow ::
  1. Data typed at keyboard
  2. Data sent via various input devices, e.g., microphone, sensor
  3. Data read from disk

The Key to File I/O ::
  For both input and output the program accessing the file must match the file organization.

Forms of Access ::
  1. Bit by bit
  2. Character by character
  3. Value by value