Computer Organization And Architecture

Step 1: Understanding Flynn’s classification.
Flynn’s taxonomy classifies computers based on the number of instruction streams and data streams.
Step 2: Characteristics of Von Neumann architecture.
Von Neumann computers execute a single instruction at a time on a single data item using a single processor.
Step 3: Matching with Flynn’s classes.
Single Instruction stream and Single Data stream corresponds to SISD.
Step 4: Final conclusion.
Therefore, Von Neumann computers are classified as SISD systems.

Step 1: Understanding top-down parsing.
Top-down parsers begin parsing from the start symbol and try to generate the input string by expanding non-terminals.
Step 2: Direction of derivation.
In top-down parsing, the leftmost non-terminal is always expanded first, while the input is scanned from left to right.
Step 3: Distinguishing from bottom-up parsing.
Bottom-up parsers construct a rightmost derivation in reverse, which is not the case here.
Step 4: Final conclusion.
Hence, a top-down parser uses a leftmost derivation.

Step 1: Understanding programmed I/O.
In programmed data transfer, the CPU is actively involved in every data transfer between the I/O device and memory. This keeps the CPU busy and prevents it from performing other useful tasks.
Step 2: Understanding DMA (Direct Memory Access).
In DMA mode, a dedicated DMA controller transfers data directly between the I/O device and the main memory without continuous CPU intervention. The CPU is only involved at the start and end of the transfer.
Step 3: Analyzing the advantage of DMA.
Since the CPU is free while the DMA controller handles data transfer, the CPU can execute other processes concurrently. This leads to better overall utilization of system resources.
Step 4: Final conclusion.
Thus, DMA improves overall system performance by allowing parallel execution of CPU tasks and I/O operations, thereby increasing concurrency.