File Access Methods

• Sequential : Blocks processed in order, one after the other
  Read operation reads the next block and updates pointer
  Write appends to the end of file
  Rewind / Forward - to skip or reach certain blocks (difficult)!
• Direct / Random : File viewed as a numbered sequence (array) of blocks
  Blocks can be read in random (any) order
• Indexed Sequential : Arrangement of records in a logical sequence - according to key contained in record
  An index from key to record
  Can access sequentially in key order or random
• Partitioned : File of sequential sub-files - for libraries etc

Space allocation USUALLY NOT contiguous - logical blocks translated to physical disk blocks