In a basic computer system, which unit or component holds data and instructions temporarily while the CPU is actively processing them?

Introduction / Context:
This question deals with the different functional units of a computer and their roles. During program execution, the CPU needs fast access to data and instructions. This is provided by primary memory, also called main memory or RAM. Distinguishing between temporary storage in primary memory and long term storage in secondary devices is a key element of computer fundamentals.

Given Data / Assumptions:

• The question focuses on where data is held temporarily while the CPU processes it.
• Options include secondary storage, output units, primary memory, input units and the power supply.
• We assume a standard von Neumann style architecture where RAM serves as main working memory.

Concept / Approach:
Primary memory, usually implemented as RAM Random Access Memory, is directly connected to the CPU and is used to store currently executing programs and data. RAM is volatile, meaning it loses its contents when power is turned off. Secondary storage devices like hard disks and SSDs keep data long term but are slower and not directly accessed by the CPU in the same way. Input units bring data into the computer, and output units send results out, but neither holds data as working storage. The power supply only provides electrical power.

Step-by-Step Solution:
Step 1: Identify that the question emphasises temporary holding of data while processing occurs. Step 2: Primary memory or RAM is specifically designed for this purpose: storing instructions and data that the CPU is currently using. Step 3: Option c directly states Primary memory unit main memory or RAM, which matches this description. Step 4: Secondary storage devices such as hard disks are non volatile and used for long term storage; they are slower and not the main temporary workspace. Step 5: Output units like monitors and printers display or print data but do not function as the CPU's active workspace. Step 6: Input units like keyboards and mice capture user input and send it to the system but are not designed to hold the working dataset. Step 7: The power supply provides electrical energy but does not store data at all. Step 8: Therefore, the correct answer is the primary memory unit.

Verification / Alternative check:
Computer fundamentals texts clearly state that the main memory temporarily stores data and instructions that the CPU needs while executing programs. Diagrams of the basic computer system show arrows between the CPU and main memory to highlight their close relationship. Secondary storage is placed outside this immediate loop. This depiction confirms that primary memory is the correct unit for temporary data storage during processing.

Why Other Options Are Wrong:
Secondary storage, while essential, serves as long term data storage and does not function as the high speed temporary workspace emphasised in the question. Input and output units are for communication with the user or external devices, not for internal data holding. The power supply deals only with electricity. Thus, none of these units meets the requirement of temporarily storing active data for the CPU.

Common Pitfalls:
Students may confuse memory and storage because both terms refer to holding data. To avoid confusion, remember that memory usually means short term, fast, volatile storage such as RAM, while storage means long term, slower, non volatile devices such as hard disks or SSDs. Associating primary with first in line to the CPU can help you remember that primary memory is where active processing data lives.

Final Answer:
The unit that temporarily holds data while the CPU processes it is the primary memory unit main memory or RAM.