15 bits
It takes 23 address lines to address 8 mb of memory.
It requires 30 address bits to address 1GB of RAM.230 = 1,073,741,824
It requires 6 bits to address 64 words. It does not matter what the word size is.
The number of address lines needed to access N-KB is given by log2N Then the number of address lines needed to access 256KB of main memory will be log2256000=18 address lines.
16384
3 bits
You need 12 address lines to access 4K of memory. 212 = 4096. log2 (4096) = 12.
9
That depends on the memory architecture of the system.if the memory chips are byte wide and not used to create a multibyte bus, 11 address bits are needed.if the memory chips are 32 bits wide, 9 address bits are needed (with the CPU internally selecting which of the 4 bytes it will use).it the memory chips are 64 bits wide, 8 address bits are needed (with the CPU internally selecting which of the 8 bytes it will use.if the memory chips are 4 bits wide, 12 address bits will be needed and the CPU must perform 2 memory cycles per byte that it needs. (yes, I have seen a computer that worked this way!)etc.
The memory address space is 64 MB, which means 226. However, each word is 4 bytes, which means that you have 224 words. This means you need log2 224 or 24 bits, to address each word.
address space=24bits => (2 Power 24)=16M words