option (d) should be correct.How (a) ?

Question

Comments

Yes option A would be the answer 2MB

Reference :https://gateoverflow.in/12059/ugcnet-dec2013-ii-49

Answer 1

#f bits we can store in a block = 128B = 2^10 bits

#f blocks = 2GB/128B = 2^24

1 block can store information about ------------------------2^10 blocks

#f blocks needed to store---------------------------------------2^24 blocks

= 2^14 blocks are needed for bit mapping

each block size = 2^7

total space req = 2^7*2^14 =2^21 = 2MB

Comments

you have done wrong calculations...

#f bits we can store in a block = 128B = 2^10 bits

#f blocks = 2GB/128B = 2^24

1 block can store information about ------------------------2^10 blocks

#f blocks needed to store---------------------------------------2^24 blocks

= 2^14 blocks are needed for bit mapping

each block size = 2^7

total space req = 2^7*2^14 =2^21 = 2MB

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typo!

Answer 2

I am getting  2MB

total number of bolck in File is  =  2GB/128B

                                                  =  16 M block

and each Block Need  1 bit in Bit map then total 16 M bit are needed to represent Bit Map in memory

memory for Bit map in Byte  = 16M bit / 8 bit

                                              =  2MB