Introduction To Computing And Internet Computer Science Essay

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Question 1

An element or device that is responsible for conversion of the data format that is suitable for human communication to a format that is acceptable for the computer is an input device.

An input device is a peripheral (a device that is connected to the computer) that is used to communicate between the user and the computer. It converts the user's information input and converts it into a language which the computer can understand.[1]

Examples of an input device: Keyboard, Mouse, Scanner.

An element or device that converts the information back from a computer oriented representation to what is suitable for human is an output device.

An output device is a peripheral that is used to communicate between the user and the computer. It receives data from the computer and converts it into a form which the user can understand.[1]

Examples of an output device: Monitor, Printer, Speaker.

An element or device that is the main resource which holds both the programs and data is the memory.

A memory stores programs and data temporarily or permanently. There are two types of data storage, short-term data storage and long-term data storage. Short-term data storage stores data that are being processed by the computer. Long-term data storage stores data that the users can retrieve. [1]

Computer memory is organized into a hierarchy according to the access time.

Untitled-1.png

Figure 1.1

(Adapted from Ryan J. Leng, 2007)

The diagram above shows that processor registers have the fastest access time among the rest. Next in the hierarchy are the L1, L2 caches. Next is the main memory.

These are the internal memory of the computer system. Below the group of internal memory in the hierarchy comes the external memory. External memory is able to store data at a cheaper rate but its access time is slower than the internal memory.

Example of internal memory: Random Access Memory (RAM).

Example of external memory: Hard Disk Drive.

An element or device that fetches instructions from main storage, interprets them and issues the necessary instructions to various parts of the computer system is the control unit.

The control unit provides control signals and timing to direct operations. It controls operations by sending out control signals to various parts of the system to perform certain functions.[1]

An element or device that conducts arithmetic and logical computation is the arithmetic logic unit (ALU).

The ALU is the core of the central processing unit (CPU). The control unit sends signal to the ALU to process the data. ALU performs operations such as addition, subtraction, multiplication, division and Boolean logic. [1]

Block Diagram of Communication Between Devices:blockdiagram.jpg

Figure 1.2

(Adapted from William Stallings, 2010, Page 19)

User inputs from the input equipment under the I/O equipment block are sent as instructions together with data to the arithmetic logical unit (ALU) and control unit (CU).

When processing the input from the I/O equipment block, the ALU communicates with the CU by exchanging instructions, data and signals.

Processed data will be stored in the internal memory temporarily. Based on the nature of the work, the data storing may not be in the internal memory all the time.

After the processing of data has been finished, data is then retrieved from the memory and storage block.

The ALU and CU will then communicate between them by exchanging instructions, data and signals while processing the output from the memory and storage block.

The processed data will then be sent back to the output device under the I/O equipment block with instruction, data and signals.

Question 2

Step 1:

Since the sign bit is 1, this tells us that it is a negative decimal number.

Step 2:

The exponent 1000 0000 is in biased excess, hence the value is:

27 - 127 = 110

Step 3:

The mantissa is 1.1 and it is negative, therefore the data will be:

-1.1 x 21 = -112

Step 4:

The binary value is then converted to denary which the decimal value is:

- (21 + 20) = -310

Question 3

Decimal value given: -1.26

Step 1:

The negative sign tell us that the sign bit is 1.

Step 2:

We then convert 1.26 to binary value which will be:

1.26 = 1.010001010001111010111 x 20

Step 3:

Since 1.010001010001111010111 x 20 is already in floating point notation and the exponent is 0, biasing it will give us 0111 1111.

Step 4:

Therefore the IEEE754 single precision format of -1.26 is:

Sign

Exponent

Significand

1

0111 1111

0100 0010 1000 1111 0101 110

Chronological Order

1

2

3

4

5

6

7

8

9

10

Action Number

B

F

D

E

I

A

G

H

C

J

Question 4

scheduling.jpg

Figure 4.1

(Adapted from William Stallings, 2010, Page 276)

Action B:

The request for Process P is sent to the long term queue of the Operating System (OS) waiting to be process. A long term queue is basically a waiting list of processes waiting to use the processor.

Action F:

When there are sufficient resources for Process P to be processed, the long-term scheduler of the OS will allocate the memory to the request of Process P and Process P is created.

The newly created Process P is then sent to the short term queue. A short term queue is a list of processes that are ready to be processed by the OS.

Action D:

In the short term queue, the short term scheduler will determine which process to be sent into the processor to execute. When Process P is being sent into the processor, the processor executes OS instructions and user processes alternately.

Action E:

Since Process P is a process that involves I/O operation, it will need access to the I/O device. Therefore, Process P is being moved to the I/O queue of the I/O device by the short term scheduler when the processor receives instruction about I/O in Process P.

Action I:

Because the processor runs at a much faster speed than the I/O operation, the processor will be idle at most of the time. In order to reduce idle time, the processor should have some other processes for it to carry out while waiting for the I/O response.

However, the main memory is full. Thus, Process P is swapped out of the main memory to create some free space for other processes.

Action A:

Process P, which is being swapped out of the main memory by the medium term scheduler to the intermediate queue is now residing on disk while waiting for the I/O operation to be complete.

Action G:

When the I/O operation is completed, the I/O module sends an interrupt request to the processor. The processor will suspend execution of its current process and ready to work on Process P.

Action H:

Process P is then moved from the I/O queue by the short term scheduler back into the short term queue for the processor to process it.

Action C:

The intermediate scheduler swaps Process P into the main memory and the processor continues the execution of Process P from where it was stopped previously.

Action J:

When Process P is completed or being stopped by the user, it will be send to the end state. The OS will then delete Process P from all the queues.

Example:

An example of this operation would be a printing job for the printer. Assume the print job is Process P.

When the user selects the print command on the computer using either a mouse or a keyboard, a request is send to the long term queue. When there are sufficient resources for the print job to be process, some memory are allocated to Process P from the main memory. Next, Process P is send to the short term queue to wait for it to be process by the processor.

Process P involves an I/O operation. An I/O operation is much slower than the processor's speed and because there are other processes other than Process P within the processor, the processor may swap Process P to the intermediate queue. At the same time, Process P is moved to the I/O queue of the I/O device because there may be other processes other than Process P that is waiting to access the device. In this case, Process P is a print job. Therefore, the I/O device is a printer and the other processes are other print jobs for the printer to carry out.

When the turn for Process P to be printed is up, it is send to the printer. As the printing speed of the printer is much slower than the processor's speed, the processor will send the data pieces by frames while alternating with the processing of other processes.

When the printing of Process P is completed, Process P will be stopped and send to the end state. The OS then delete Process P from all queues.

Conclusion

The computer system is made up of major components. The major components are the processor, main memory and the I/O equipments. The major components communicate with each other via data and signals processed by the Arithmetic Logic Unit (ALU) and send out by the Control Unit (CU).

The computer system only works on binary digits and IEEE 754 is a standard for floating point data storage.

Operating System (OS) manages different processes in the computer system by scheduling. There are four major types of scheduling. They are the long term scheduling, short term scheduling, medium term scheduling and I/O scheduling. In the case when there is an I/O operation, swapping is performed so as to increase the efficiency usage of the main memory for process execution.

Learning Outcome

Firstly, we have learned about the various components in a computer system and how they work together and carry out a certain function.

Next, as the computer only works on binary digits, we have learned how to represent data in IEEE 754 by converting from a denary number and vice versa.

Lastly, we now understand the whole process of scheduling performed by the OS. Memory management is also another task performed by the OS and both are important in a multiprogramming system.

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