A2 computing 2012-2013 bath.

[Ravichandran]

Dear A2 students,

                               It is indeed a great privilege for me to welcome all of you to this A2 computing class, which stared June 2012. I wish you have all had a great experience in you AS level computing where you had learned programming and theory in your own way. From my side, I have always seen you all as students who have good knowledge in programming. However, coming to the theory, I am sorry to say that you have not met my requirements, most of the time you answers have deviated from the examiners requirement and as such, you have lost marks heavily in theory. Now, please dont take the same experience and attitude with you in your A2 computing course, you may sure end up landing no where. So, right from the beginning, inculcate the habit of reading more into the subject thought and sure reading alone would provoke you to bring dozens of questions to classroom discussions. I dont want the classroom to be an passive teaching place or an active learning place, I want the classroom to be a flipped classroom. That is where the students experience are discussed in the classroom and the problems are solved. This alone can get you a A grade. For this, you need to have your reading habit to go on and on on a daily basis until the end of the A2 course. Hope all of you would take this A2 course very serious and fill in your intellectual void with my words of wisdom taken from the CIE oven and served to you hot.

All the best,

Keep moving,

Dr.Ravi   

[2ur8dmrc0puwv]

Mention the register to execute the program and explain the use of each registers

1. Program Counter (PC)  - This register fetches instructions and increments the address memory
2. Current Instruction Counter (CIR) – The current instruction register stores the instruction that is currently being executed
3. Memory Address Register (MAR) – The memory address register stores the address of data or instructions that are to be accessed from main memory
4. Memory Data Register (MDR) – The memory data register stores data that has been read from, or is about to be written to, the main memory.
5. Index Register -  A register used to determine the address of an operand

Explain the Fetch-Decode-Execute-Cycle (9 Steps)

1. CPU reads the PC for next instruction address

2. Contents of the PC moved/copied to the MAR

3. Memory Address is searched, content of address copied to MDR

4. PC increments by one

5. Content of MDR copied to CIR

6. Content (Instructions) in CIR is decoded

7. Execute instructions (command)

8. Repeat step 1

How do you explain the fetch-decode-execute cycle using the pseudo code algorithm?

1. MAR  <- [PC]
2. PC  <- [PC] + 1
3. MDR  <- [[MAR]]
4. CIR  <- [MDR]
5. DECODE
6. EXECUTE
7. GO TO STEP 1

What is parallel, array, and math-co processor?

1. Parallel – Simultaneous use of more than one processor to execute a program
2. Array – An array processor implement the instruction set where each instruction is executed on all data items associated and then move on the other instruction.
3. Math co Processor – a processors that allows a computer to perform mathematical calculations more efficiently and faster, increases the overall speed of a computer in many places.

 

[3ckv6ewo262qp]

Raj Kumaran Kalidas said:

Exercise Chapter 3.

[Ahmad Syahmi Irfan]

19/2/2013

[Dain Razali]

1. Mention the registers used to execute a program and explain the use of each register.

2. Explain the fetch-decode-execute cycle. (9 steps)

3. How do you explain the fetch-decode-execute cycle using the pseudocode algorithm

4. What is parallel-processor, array-processor, maths co-processor.

Solution

1. a) Program Counter (PC)

Stores the address of the next instruction to be fetched. The value of the PC will be incremented everytime an instruction is accessed.

b) Memory Address Register (MAR)

When the next address is needed, its address is copied from the PC and placed in the MAR.

c) Memory Data Register (MDR)

Address is found using the MAR and the contents are placed in the MDR.

d) Current Instruction Register (CIR)

Contents from the MDR are subsequently copied into the CIR. The CIR holds the instruction that is about to be executed. Once called for, the instruction in the CIR is split into its individual parts.

e) Index Register (IR)

Used to modify operand addresses during the run of a program.

******************************************************************************************************************************************************

2. The 'fetch' stage:

a) Copy the address in the program couner (PC) into the memory address register (MAR).

b) Increment the PC (preparation for the next fetch)

c) Load the instruction in the MAR into the memory data register (MDR)

d) Load the instruction in the MDR into the current instruction register (CIR).

The 'decode' stage:

e) Identify the type of addressing used by the instruction.

i) If it is a direct address, load a copy of the address into the MAR and retrieve the contents of the address.

ii) If it is an indexed address, add the address to the contents of the index register (IR) and copy the result to the MAR.

f) Decode the instructions.

The 'execute' stage:

g) If the instruction is a jump instruction then:-

i) Load the address operand to the PC

ii) Go to Step (a)

h) Execute the instruction.

i) Repeat the cycle (Go to step (a)).

****************************************************************************************************************************************

3. Using pseudocode algorithm:

a) MAR <== [PC]

b) PC <== [PC] + 1

c) MDR <== [[MAR]]

d) CIR <== [MDR]

e) Decode

f) Execute

g) Go to Step (a)

*******************************************************************************************************************************************

4. a) Parallel processor

- Has more than one processor working on the job.

- Works on the task by splitting the task into sub-tasks and allocating them to different processors to be processed simultaneously.

- Used to produce weather forecasts.

b) Array processor

- Data locations can be processed simultaneously when there is similar calculation to be done for each location.

- Used to simulate the effect of a single action on a number of points on a car chassis.

c) Maths co-processor

- Registers are long enough to handle floating-point numbers as single data values.

- Increases performance by reducing the number of operations that need to be carried out. Used in graphics-demanding applicationsas the calculations are time sensitive and the screen requires a high frame rate.

[Muhammad Mujahid Lokman]

19/2/2013 class assignment