Identify the correct order of the following computer memories on the basis of…

Concept

Memory access time is the delay between requesting a data item and receiving it. Computer memories form a hierarchy: the closer a memory sits to the CPU's execution core, the faster (lower access time) but smaller it is, while memory farther away is larger but slower. Ordering by increasing access time therefore means going from the memory nearest the processor outward to the most distant storage.

Applying the hierarchy

Rank the four memories from nearest-to-the-core (fastest) to farthest (slowest):

1. Registers: sit inside the CPU and are read in well under a nanosecond — the lowest access time.

2. Cache memory: SRAM placed between the CPU and main memory; a few nanoseconds — slower than registers, faster than RAM.

3. Main memory (RAM): DRAM accessed over the memory bus; tens of nanoseconds — slower than cache.

4. Secondary memory (disk/SSD): accessed over an I/O path; microseconds to milliseconds — by far the highest access time.

Increasing access time (low to high) is therefore Registers, then Cache, then Main Memory, then Secondary Memory.

Cross-check

This is exactly the reverse of the speed ordering and of the cost-per-bit ordering: registers are the costliest and fastest per bit, secondary memory the cheapest and slowest. Reading the standard pyramid top-down gives the same sequence, confirming the order Registers → Cache → Main Memory → Secondary.