In older personal computers, the size of primary memory (main memory or RAM) typically ranged between which of the following values?

Introduction / Context:
This question refers to the historical configuration of early personal computers rather than modern systems. In the early days of PCs, main memory capacities were very small compared with today, and typical exam questions still refer to these values as part of basic computer history. Understanding how primary memory sizes have evolved over time helps learners appreciate advances in hardware and recognise classic specifications that may appear in competitive exam syllabi.

Given Data / Assumptions:

• The focus is on primary memory, also called main memory or RAM, in early personal computers.
• The question asks for the range in which this memory typically fell.
• Options list several ranges measured in kilobytes and megabytes.
• We assume reference to classic systems where the widely known upper limit was 640 KB of conventional memory.

Concept / Approach:
In the early generation of IBM compatible personal computers, conventional memory was limited to 640 KB due to design constraints in the addressing scheme. Typical systems shipped with at least 256 KB of RAM and could be expanded up to 640 KB of primary memory that was directly usable by the operating system and applications. Very small values such as 2 KB to 8 KB are characteristic of microcontrollers or older home computers, not the widely recognised IBM PC range. Larger sizes in megabytes became common later. Therefore, the historical exam oriented range usually cited for primary memory in early PCs is 256 KB to 640 KB, making that option the correct answer.

Step-by-Step Solution:

Verification / Alternative check:
Historical documentation and computer history summaries often mention 640 KB as the conventional memory limit on early PCs, with extended memory available only through special techniques. They describe common configurations such as 256 KB, 512 KB and 640 KB of RAM. Smaller amounts like 64 KB were more common in early home computers and microcomputers that predated the IBM PC standard, while megabyte level memory became typical only in later generations. Exam preparation books for computer awareness usually repeat the range 256 KB to 640 KB when discussing the size of primary memory in early PCs, confirming that this is the expected answer.

Why Other Options Are Wrong:

• 64 KB to 256 KB: Reflects capacities of some early microcomputers but does not include the well known 640 KB limit of classic PCs.
• 256 KB to 512 KB: Misses the common upper boundary of 640 KB that is emphasised in exam oriented material.
• 2 KB to 8 KB: Far too small and more characteristic of simple microcontrollers, not mainstream early PCs.
• 1 MB to 4 MB: These sizes became common later and do not describe the typical range of primary memory in the earliest IBM compatible personal computers.

Common Pitfalls:
Because modern computers have gigabytes of memory, learners sometimes underestimate how small early memory sizes were and guess ranges in megabytes. Others may have heard 640 KB mentioned without remembering the lower end of the range. To handle such questions, it helps to memorise the classic line that early PCs had primary memory ranging from around 256 KB up to a conventional limit of 640 KB. When you see exam options that include this specific range, it is usually the correct answer for questions about the size of primary memory in early personal computers.

Final Answer:
In early personal computers, the size of primary memory typically ranged between 256 KB to 640 KB.