will change the data in the segment in which case the line may become compressible therefore at step 535 if it is determined that the miss is a write access control proceeds to step 540 where a determination is made as to whether f lt tc that is if the number of free blocks is below the threshold tc or whether the fifo is full if f is equal to or greater than tc and the fifo is not full then at step 542 the directory entry k is inserted in the fifo and the u201c in fifo u201d flag bit is set at step 543 otherwise at step 540 if f is less than tc control proceeds to step 541 which initiates two parallel sequences of operations the first sequence comprises steps 542 and 543 wherein the directory entry k is inserted in the fifo and the u201c in fifo u201d flag bit is set however since the number of free blocks has fallen below the threshold or the fifo is full an item is removed from the fifo which entails logically removing a segment from the virtual uncompressed cache this is accomplished by the following steps at step 525 a directory index k u2032 is found by removing the item at the tail of the fifo at step 526 having found and read entry k u2032 the u201c in fifo u201d flag bit is cleared for the entry k u2032 at step 527 the segment k u2032 is read from memory and at step 528 the segment k u2032 is compressed and stored back to memory where one possible result as.