Discussion
How many address lines are needed to address 1 KB of memory?
Answer: D
Correct answer: 10
With \( n \) address lines a processor can select \( 2^{n} \) distinct locations. Since 1 KB in the binary sense is 1,024 bytes, \[ 2^{n} = 1024 \quad\Rightarrow\quad n = 10. \] The powers of two are worth having by heart for this family of questions: \( 2^{10} = 1\text{K} \), \( 2^{20} = 1\text{M} \), \( 2^{30} = 1\text{G} \). So 1 MB needs 20 address lines and 4 GB needs 32 - which is precisely why a 32-bit processor can address no more than 4 GB without extensions. The distractor 1024 confuses the number of locations with the number of lines needed to select among them. The width of the data bus is a separate matter: it determines how many bits are transferred at once, not how many locations exist. A memory of 1K × 8 has ten address lines and eight data lines.
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