Basic Computer Organisation Questions and Answers

Answer: C

The register used in arithmetic is the Accumulator.

In the 8085, the accumulator (register A) holds one operand of every arithmetic and logic operation, and the result is stored back in it.

The stack pointer holds the address of the top of the stack, the program counter the address of the next instruction, and 'instruction pointer' is the 8086's name for its program counter, not an 8085 register.

Answer: D

The answer is All of the above.

The 8085 flag register contains the Sign, Zero, Auxiliary Carry, Parity and Carry flags. The zero, carry and sign flags named in the options are all among them.

Choosing any single flag would leave out the other two, which are also present.

Each flag is a single bit set by the result of an operation: Zero when the result is 0, Carry on a carry out of bit 7, and Sign when bit 7 of the result is 1.

Answer: B

The Program Counter stores the address of the next instruction to be executed.

After each instruction is fetched, the PC is advanced so that it always points to the next instruction in memory. Jumps, calls and returns work by loading a new address into it.

The instruction being executed is held in the instruction register, data is stored in memory and registers, and arithmetic is done by the ALU.

Answer: C

The Control Unit manages and coordinates the execution of instructions.

The CU fetches each instruction, decodes it and generates the control signals that tell the ALU, registers, memory and input/output devices what to do and when. It directs the work but does not itself compute.

The actual arithmetic and logic is done by the ALU, data is stored in memory, and input/output is handled by I/O devices under the CU's direction.

Answer: B

In a von Neumann architecture, instructions and data are stored in a shared memory space.

The stored-program concept puts programs and data in the same memory, reached over the same bus. This simplicity is also its limit, the 'von Neumann bottleneck', since instructions and data cannot be fetched at once.

Separate memory spaces for instructions and data is the Harvard architecture. The control unit and cache are not where the program is stored.

Answer: A

Registers store data temporarily during program execution.

Registers are small, very fast storage locations inside the CPU that hold the operands, results, addresses and status information the processor is working on at that moment.

Computation is done by the ALU, long-term storage is the job of secondary memory, and data transfer to I/O devices is managed by I/O controllers and the OS, not by registers.

Answer: D

The condition is called bus contention.

Bus contention occurs when two or more devices drive the same bus lines at the same time, one pulling a line high while another pulls it low. The data is corrupted and the drivers can be damaged by the current, which is why devices use tri-state outputs and bus arbitration so that only one drives the bus at a time.

Address multiplexing sends row and column addresses over the same lines at different times, and address decoding selects a device from an address. 'Collision' is the term for simultaneous transmissions on a network such as Ethernet.

Answer: D

A complete microcomputer system consists of all three, so the answer is All of the above.

It needs a microprocessor to execute instructions, memory to hold programs and data, and peripheral equipment such as input and output devices and storage, so that it can communicate with the user. Any one of the three alone is only a part of the system.

Answer: C

A computer adds and compares data in the CPU chip.

Arithmetic and logic operations are done by the arithmetic logic unit inside the central processing unit, which adds numbers and compares them. The hard disk (A) and the floppy disk (B) are storage devices, and the memory chip (D) holds data and instructions but does no calculation.