In a computer system, what is the main job of the CPU (Central Processing Unit) with respect to programs and data processing?

Introduction / Context:
The CPU, or Central Processing Unit, is often called the brain of the computer because it performs the core computing work. It interacts with memory and input or output devices to execute instructions and manipulate data. Understanding the primary responsibilities of the CPU helps clarify how a computer actually performs tasks specified by software.

Given Data / Assumptions:

• The component under discussion is the CPU.
• Options mention carrying out program instructions, storing data for future use, processing data and information, and a combined choice.
• We assume a standard von Neumann architecture where CPU executes instructions stored in memory.
• Data storage for long term use is usually handled by memory and storage devices, not by the CPU itself.

Concept / Approach:
The CPU reads program instructions from memory, interprets them, and executes them. These instructions usually involve processing data, such as performing arithmetic, comparisons, or logical operations. This means the CPU both carries out program instructions and processes data and information. Long term storage is primarily handled by memory and disk storage, not the CPU. Therefore, option A (carry out instructions) and option C (process data and information) are both correct descriptions of the CPU's main job, so the combined option “both (a) and (c)” is the best answer.

Step-by-Step Solution:
Step 1: Consider whether the CPU carries out program instructions. Yes, the CPU fetches, decodes, and executes instructions from memory. Step 2: Consider whether the CPU stores data for future use. Long term storage is handled by RAM and disk; the CPU may have registers but does not mainly store data for future use. Step 3: Consider whether the CPU processes data and information. Yes, the CPU performs arithmetic and logical operations on data as part of instruction execution. Step 4: Identify which options correctly describe the CPU's main functions. Option A and option C are both correct, while option B is not the primary job. Step 5: Choose the combined option “both (a) and (c)”.

Verification / Alternative check:
Descriptions of the CPU in basic textbooks emphasise the instruction cycle: fetch, decode, execute. The execute phase involves processing data, which clearly matches options A and C. They also describe the memory unit and storage devices as responsible for storing data and programs. CPU registers provide temporary working storage but not long term retention. This consistent description confirms that the CPU mainly executes instructions and processes data, not primarily stores it for future use, and supports the combined answer.

Why Other Options Are Wrong or Incomplete:
Option A (carry out program instructions): Correct but incomplete, because it does not explicitly mention processing data, which is a key part of execution. Option B (store data/ information for future use): This describes the role of memory or storage more than the CPU. Option C (Process data and information): Correct but incomplete without stating that the CPU follows program instructions.

Common Pitfalls:
Learners sometimes think the CPU does everything, including storing data, simply because it is described as the brain. Others choose only one of the correct aspects and miss the combined option. To avoid this, remember that the CPU specialises in executing instructions and processing data, while memory and storage specialise in retaining data. When a combined answer summarises both execution and processing, it usually best captures the CPU's main job.

Final Answer:
The main job of the CPU is to carry out program instructions and process data and information, that is, both (a) and (c).