CSF: Boring Stuff

Question 1

Name the 6 Storage Units in Order (Smallest to Largest)

Answer 1

Bit
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte

Question 2

Name all the Components in the CPU?

Answer 2

Control Unit, ALU, Accumulator, Instruction Register, Program Counter, Memory Address and Memory Data

Question 3

What does the CU (Control Unit) do?

Answer 3

It decodes, controls and co-ordinates everything that happens within the CPU

Question 4

What does the Arithmetic & Logic Unit (ALU) and the Accumulator do?

Answer 4

The ALU makes calculations and makes decisions while the Accumulator holds the data being manipulated by the ALU

Question 5

What does the Instruction Register do?

Answer 5

Holds the instruction currently being decoded by the CU

Question 6

What does the Program Counter do?

Answer 6

Keeps track of the point we have reached in the program

Question 7

What does the Memory Address Register (MAR) and the Memory Data Register (MDR) do?

Answer 7

The MAR points to the exact memory location in RAM of the data/instructions being fetched or written and the MDR is a ‘transfer zone’ for data being transferred between the memory and CPU

Question 8

Name all three buses and explain them

Answer 8

Control Bus - Connects the CU to all other components and it carries timing and control signals. This bus is bi-directional as the CU sends out control signals and receives acknowledgements.

Data Bus - Allows data to be passed between the CPU and RAM. This bus is bi-directional as well meaning data can flow in both directions between the MDR and the RAM.

Address Bus - Connects the Memory Address Register to the RAM and it carries binary signals which prepares the cell to send or retrieve data. This bus is uni-directional meaning it only carries points from the MAR to the RAM,

Question 9

How to Calculate the Number of Cells in the Address Bus?

Answer 9

2^width of the address bus

Question 10

Is RAM volatile or not?

Answer 10

It is volatile meaning it loses all stored information when it loses power.

Question 11

What is the role of the ROM chip?

Answer 11

Its role is to start the computer, perform the Power On Self Test (POST), load basic input and output services, then load the OS. Also, the ROM chip is non-volatile.

Question 12

Explain cache

Answer 12

The cache is memory which sits between the RAM and the CPU. When the processor needs to read/write to a location in the processor it can first check if the data can be found on the cache and if it is it will just read/write to the cache which is much quicker.

Question 13

What is a Device Driver?

Answer 13

A dedicated piece of software that enables Hardware to communicate to the OS. They also pass data to and from the peripheral.

Question 14

What is Polling Approach?

Answer 14

Polling is when the processor goes round each device in turn and see’s if they require any resources

Question 15

Name an Advantage and Disadvantage of Polling

Answer 15

Ad - Easy system to implement
Dis - Once the processor has moved on, a device has to wait on its turn again

Question 16

What is the Interrupting Approach?

Answer 16

Interrupting is when the device goes to the processor with its request and interrupts what its doing

Question 17

Name an Advantage and Disadvantage of Interrupting

Answer 17

Ad - Devices requirements can be met much quicker
Dis - Its a complex system to implement

Question 18

What is the Interrupt Service Routine (ISR)?

Answer 18

When an interrupt request reaches the CPU, it causes the CPU to interrupt the task that it was doing and change to the ISR. Once an IRQ is accepted by the CPU, it must identify the source of the request and locate the appropriate ISR in memory. The PIC identifies the IRQ responsible for the
interrupt. When the ISR is completed, the CPU returns to the program it was executing and resumes its previous task.

Question 19

What is the stack?

Answer 19

A dedicated piece of RAM that stores all the values the CPU dumps onto it when dealing with an interrupt and when its done the contents within the Stack are popped back into the CPU

Question 20

Explain Direct Memory Access (DMA)

Answer 20

A system where the transfer of data is directly set up between the peripheral and RAM which runs without the use of the CPU. This is all set up by the DMAC.

Question 21

Advantage and Disadvantage of DMA

Answer 21

Frees the CPU to get on with other things and it completes the process of transferring data much quicker.

DMA requires both the entire bus system and the RAM and if the CPU requires the bus system or RAM while the DMAC is using it, the DMAC takes priority which could cause memory loss in the CPU.

Question 22

What does the DMAC need to set up the DMA process?

Answer 22

The memory start address, the quantity of data, the device involved and whether the transfer if an input or output.

Question 23

What are the Five Layers of the OS?

Answer 23

User Interface (UI)
File Management System
Input/Output
Memory Management
Kernel

Question 24

What is the purpose of the File Management System?

Answer 24

To organise and manage the storage of data on permanent data

Question 25

What is the purpose of the Input-Output Layer?

Answer 25

Manages communications between peripherals and CPU and if another layer needs access to a device they send a request to the I/O layer

Question 26

What is the purpose of the Memory Management Layer?

Answer 26

Shares the physical memory of the computer between processes and programs

Question 27

What does the MML do when there isn’t enough physical memory?

Answer 27

Uses virtual memory

Question 28

What is Thrashing?

Answer 28

Thrashing is when a workload cannot be held effectively within the physical memory and the constant swapping of data makes a sound. Thrashing negatively effects the computers performance

Question 29

What is the Kernel?

Answer 29

The Kernel is the most protected layer of the OS and its responsible for handling things such as multi-tasking, process control, error handling and interrupt management.