LRU APPROXIMATION PAGE REPLACEMENT ALGORITHM

• use of reference bit page replacement can be done if the system does not support hardware 
• reference bit is set by the hardware,when the page is referenced.
• reference bits are associated with entry in the page table
• initially all the bits are cleared to 0 by the OS
• when process executes,the bit associated with each page referenced is set to 1 by the hardware
• from the reference bits,can determine which page is used and not
• need not know the order of use,but know which pages are used.