In computer systems, why is secondary storage such as hard disks or SSDs needed in addition to primary memory (RAM)?

Introduction / Context:
Computer systems use both primary memory (RAM) and secondary storage devices such as hard disk drives and solid state drives. While RAM is very fast, it has limitations related to volatility and capacity. Secondary storage solves some of these limitations and plays a crucial role in storing operating systems, applications, and user data. This question asks why secondary storage is needed, highlighting two key properties that make it essential.

Given Data / Assumptions:

• We are comparing secondary storage with primary memory such as RAM.
• The options mention no need of power supply, large storage capacity, both properties, none of the above, and an unrelated performance statement.
• We assume basic knowledge of how data behaves in RAM versus on a disk.
• We focus on typical magnetic or solid state storage devices used in personal computers.

Concept / Approach:
Primary memory (RAM) is volatile, meaning that it loses its contents when power is turned off. It is also relatively expensive per unit of storage, so practical systems include only a limited amount. Secondary storage, such as hard disks or SSDs, is non volatile, retaining data even when the system is shut down, and offers much larger capacity at a lower cost per unit of data. Therefore, the main reasons for using secondary storage are its non volatility and large capacity, not directly increasing processor speed.

Step-by-Step Solution:
Step 1: Recall that RAM clears its contents when the computer is powered off, while secondary storage keeps data until it is explicitly erased.Step 2: Recognise that operating systems, applications, user documents, and media files must persist across reboots, which is possible only with non volatile storage.Step 3: Understand that modern hard disks and SSDs can store hundreds of gigabytes or terabytes of data, far more than typical RAM sizes.Step 4: Compare the options: option A refers to non volatility (no need of continuous power), and option B refers to large storage capacity.Step 5: Note that both properties are correct and together explain the need for secondary storage.Step 6: Conclude that option C, Both A & B, is the correct choice.

Verification / Alternative check:
To verify, think about what would happen if a computer had only RAM and no hard disk or SSD. Every time the system lost power, all programs and data would vanish, requiring the user to reinstall everything from scratch. Also, storing large video files, databases, or game installations would be impossible because RAM is limited and expensive. In reality, we install the operating system and applications on secondary storage and load parts of them into RAM only when needed. This real world scenario confirms that non volatility and high capacity are the primary reasons for using secondary storage.

Why Other Options Are Wrong:
Option A alone is incomplete because although non volatility is important, capacity is also a major reason for using secondary storage. Option B alone ignores the critical need for data to survive power off events. Option D, None of the above, is incorrect because both A and B are valid reasons. Option E, To increase processor speed, is misleading; while faster storage can reduce load times, processor speed is mainly determined by CPU design and clock frequency, not by the presence of secondary storage. Therefore, the combined option Both A & B is the only fully accurate choice.

Common Pitfalls:
Some learners may focus on one benefit of secondary storage and overlook the other, selecting only non volatility or only capacity. Others might mistakenly believe that secondary storage exists primarily to make the computer faster, confusing storage performance with processor speed. It is helpful to remember that RAM is like a fast work area for current tasks, while secondary storage is like a large, reliable archive where everything is kept even when the system is turned off. This mental model clarifies why both listed properties matter.

Final Answer:
Secondary storage is needed because it is non volatile and offers high capacity, so the correct choice is Both A & B.