Which computer architecture has one instruction stream and one data stream?

The correct answer is A: SISD. SISD stands for Single Instruction, Single Data. This computer architecture model, part of Flynn's Taxonomy, describes a traditional uniprocessor system where there is one control unit that fetches a single stream of instructions and processes a single stream of data. Most traditional von Neumann architecture computers fall into this category, executing instructions sequentially on individual data items. This is the simplest and most common form of computer architecture.

• B: MIMD is incorrect. MIMD stands for Multiple Instruction, Multiple Data. This architecture features multiple processors that can simultaneously execute different instructions on different data streams. This is characteristic of modern multi-core processors, distributed systems, and parallel computers.
• C: MISD is incorrect. MISD stands for Multiple Instruction, Single Data. This is a less common architecture where multiple processors execute different instruction streams on the same data stream. Examples are rare, but it can be found in specialized fault-tolerant systems or pipeline architectures where different operations are performed on the same data in sequence.
• D: SIMD is incorrect. SIMD stands for Single Instruction, Multiple Data. This architecture involves a single instruction being executed simultaneously on multiple data items. This is common in vector processors and graphics processing units (GPUs), which are highly efficient for tasks like image processing, scientific computing, and multimedia operations where the same operation needs to be applied to a large dataset.