Computer Architecture

Step 1: Interpret 2's complement numbers.
1101 (4-bit 2's complement) =
0100 (4-bit 2's complement) =
Step 2: Add the two values:
Step 3: Binary addition:
Step 4: Overflow check:
One number is negative, one is positive → No overflow. But if considering MSB change in sign bit, question might interpret overflow differently.

Note: The widely accepted answer is (3) DMA (Direct Memory Access), as it is designed specifically to handle data transfer between memory and peripherals without CPU intervention.
However, if DDA (Digital Differential Analyzer) is considered in this context (e.g., in specialized systems or questions where DDA has a broader functional meaning), it may be marked as correct based on specific syllabus or exam keys.

Cache memory is a small, fast memory located near the CPU. It acts as an intermediary between the CPU and the main memory (RAM) to speed up data access by storing frequently accessed data.
Understand the function of cache memory.
Cache memory stores copies of frequently accessed data from RAM to speed up the CPU’s access to data. When the CPU needs data, it first checks the cache, and if the data is not found, it fetches it from RAM. Thus, the correct answer is:

Step 1: Let's analyze the statements:

- I. Hardware control units are faster, but their design is more rigid and difficult to modify compared to microprogrammed control units, which are flexible and easier to modify. Thus, this statement is true.
- II. In horizontal microprogramming, each control signal is represented by a separate bit, making it more parallel but also increasing the control word length. This statement is true.
- III. Vertical microprogramming typically has shorter control words but sacrifices parallelism because fewer control signals are available. This statement is incorrect, as vertical microprogramming usually does not provide greater parallelism.
- IV. Microprogrammed control units are generally easier to modify and implement compared to hardware control units, which are hardwired and less flexible. This statement is true.

Step 2: Based on this analysis, the correct answer is (a) because statements I, II, and IV are correct, while statement III is incorrect.

In the given system:
- The CPU has 6 registers.
- Each instruction is 32 bits wide.
- Each instruction involves two registers and one memory address.
Let's break this down:

1. Registers: With 6 registers, the number of ways to choose 2 registers for an instruction is given by the combination formula , which represents selecting 2 registers out of 6. 2. Memory address: The main memory size is 512 KB, which means we need to address 512 x 1024 bytes = locations. Since each memory address is 19 bits, there are possible memory addresses. 3. Total distinct instructions: The number of distinct instructions is the product of the number of ways to choose the registers and the number of possible memory addresses. Hence, the total number of distinct instructions is: The number of distinct instructions is thus , which is 128 distinct instructions when considering the register and operand combination. Thus, the correct answer is .