I'm struggle on this practice question from this site....

Calculate the number of bits required in the address for memory having size of 16 GB. Assume the memory is 4-byte addressable.

MY QUESTION IS: what is the difference between an "address" and "the memory is 4 byte addressable"?

I understand an address would be its location in memory that is represented by bits, such as 2^n, where n is the number of bits in the address. But I'm confused about addressable in this question and how that's different than address

2^n * 4 bytes = 2^34 The solution is 32 bits

• On further research I think that the address is the unique location of the memory, and the addressable is how much data can be stored at that address.... that's what I got from this site: leescomputingblog.wordpress.com/2011/12/07/… Aug 23, 2020 at 13:15
• Address is a label that identifies a memory location. The memory is $4$ byte addressable means that you have labels that refer to memory locations of size $4$ bytes. You don't have names for smaller sizes. For example, if we have a memory of $12$ bytes and the memory is $4$ byte addressable, then we can have $3$ blocks of memory to which we can assign an address. Their addresses could be Memory block 1, The glorious block 2 and Ceres. Instead of fancy long name what is common is for the addresses to be binary numbers. Since there are $3$ addresses, then we need at least $2$ bits.
– plop
Aug 23, 2020 at 13:37
• In your problem, instead of $12$ bytes, you have $16$ GB ${}=2^{10}$ bytes. The memory is $4$ byte addressable. So, we can have $2^{10}/4=2^8$ different addresses. So, we need $8$ bits to encode all addresses.
– plop
Aug 23, 2020 at 13:41
• @plop Make an answer? Aug 23, 2020 at 15:11

Address is a label that identifies a memory location. The memory is $$4$$ byte addressable means that you have labels that refer to memory locations of size $$4$$ bytes. You don't have names for smaller sizes. For example, if we have a memory of $$12$$ bytes and the memory is $$4$$ byte addressable, then we can have $$3$$ blocks of memory to which we can assign an address. Their addresses could be Memory block 1, The glorious block 2 and Ceres. Instead of fancy long names what is common is for the addresses to be binary numbers. Since there are $$3$$ addresses, then we need at least $$2$$ bits.
In your problem, instead of $$12$$ bytes, you have $$16$$ GB $${}=2^{34}$$ bytes. The memory is $$4$$ byte addressable. So, we can have $$2^{34}/4=2^{32}$$ different addresses. So, we need $$32$$ bits to encode all addresses.