AS/A2 computing 2013 July batch

[Ravichandran]

Dear students of Block 6 AS computing, welcome to the computing class. I am your facilitator Dr.Ravichandran ( you can call me Dr.Ravi), I will be your course facilitator for AS computing and A2 computing. I will start communicating with you in this discussion forum - where you can start posting your queries and useful resources.

You are highly encouraged to interact with me and also with your peers as the class begins from 30th July 2013.

All the best and keep moving. Do not hesitate to ask and send your queries if you have one.

Regards,

Dr.Ravichandran

i HAVE ATTACHED THE SYLLABUS TOO.

YOU CAN DOWNLOAD THE ATTACHMENT FILE.

[Ariel Logujin Takom]

Programming for 15th April 2014, to find the number of the word 'THE' repeating in a given sentence.

Private Sub Command1_Click()
Dim x As String
MsgBox "Hi! This is a program to find the number of times the word 'the' is repeated in a given sentence! :D'"

x = InputBox("Please input your sentence.")
j = Len(x)
For i = 1 To j
If Mid$(x, i, 3) = "the" Or Mid$(x, i, 3) = "The" Then Rptn = Rptn + 1 'Rptn is variable name
Next i
MsgBox "The number of 'the' in the sentence is/are " + Str(Rptn) + " number of times."

End Sub

[Ariel Logujin Takom]

Ammendments for my code:

Private Sub Command1_Click()
Dim x As String
MsgBox "Hi! This is a program to find the number of times the word 'the' is repeated in a given sentence! :D'"

x = InputBox("Please input your sentence.")
j = Len(x)
For i = 1 To j
If Mid$(x, i, 5) = " the " Or Mid$(x, i, 4) = "The " Then Rptn = Rptn + 1 'Rptn is variable name
Next i
MsgBox "The number of 'the' in the sentence is/are " + Str(Rptn) + " number of times."

End Sub

[Muhammad Aiman bin Hashim]

1. Paging

memory managements schemes of which a computer can retrieve and store data from secondary storage to the main memory in same size blocks called pages

2. Segmentation

division of computer's main memory in segments.

3. Fragmentation

phenomenon in which the storage space is used efficiently, reducing capacity or performanceand often both.

4. Virtual memory

memory management technique that uses both hardware and software. . It maps memory addresses used by a program, called virtual addresses into physical addresses in computer memory.

 

5. Page Table

A page table is the data structure used by a Virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM.

6. Swapping

When the physical memory in the system runs out and a process needs to bring a page into memory then the operating system must decide what to do. It must fairly share the physical pages in the system between the processes running in the system, therefore it may need to remove one or more pages from the system to make room for the new page to be brought into memory.

[Raid Syamil]

VIRTUAL MEMORY

In computing, virtual memory is a memory managment technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage as seen by a process or task appears as a contiguous address space or collection of continuous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.

 

PAGE TABLE

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses  and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM.

FRAGMENTATION

In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

DEFRAGMENTATION

In the maintenance of file systems, defragmentation is a process that reduces the amount of fragmentation. It does this by physically organizing the contents of the mass storage device used to store files into the smallest number of contiguous regions (fragments). It also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmentation utilities try to keep smaller files within a single directory together, as they are often accessed in sequence.

Defragmentation is advantageous and relevant to file systems on electromechanical disk drives. The movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to seek other fragments.

PAGING

In computer operating systems, paging is one of the memory-management schemes by which a computer can store and retrieve data from secondary storage for use in main memory. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. The main advantage of paging over memory segmentation is that it allows the physical address space of a process to be noncontiguous. Before paging came into use, systems had to fit whole programs into storage contiguously, which caused various storage and fragmentation problems.

Paging is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use secondary storage for data that do not fit into physical random access memory (RAM).

SWAPPING

(In many programming languages where the swap function is built-in; in C++,overloads are provided allowing std::swap to swap some large structures in O(1) time.) After swap() is performed, x will contain the value 0 and y will contain 1; their values have been exchanged. Of course, this operation may be generalized to other types of values, such as strings, aggregated data types and comparison sorts, utilize swaps to change the positions of data.

[Ahmad Ammar Rashid]

1) Paging is a method of writing data and reading it from from secondary storage for use in primary storage. Its a fixed-length contiguous block of virtual memory, described by a single entry in the page table.

2) Memory segmentation is the division of a computer's primary memory into segments or sections. Segments usually correspond to natural divisions of a program such as individual routines or data tables so segmentation is generally more visible to the programmer than paging alone

3) Fragmentation is when data file over a certain size is stored in several segments rather than one contiguous sequence of bits in one place on the storage medium. 

4) Virtual memory is a section of a hard disk that's set up to emulate the computer's RAM.

5) A page table is the data structure used by a virtual memory system in a computer OS to store the mapping between virtual addresses and physical addresses.

6) Swapping is an older form of memory management similar to paging. It uses a space on the hard disk as a virtual memory"s extension of the computer's real memory RAM. The computer OS will pretend that you have more RAM than you actually do.

[MOHAMMAD LUQMAN B MOHD RADZAI]

1) What do you know about the following :

a) PAGING

Paging is one of the memory-management schemes by which a computer can store and retrieve data from secondary storage for use in main memory. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. 

Paging is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use secondary storage for data that do not fit into physical random-access memory (RAM).

b) SEGMENTATION

1) Packet segmentation, the process of dividing a data packet into smaller units for transmission over a data        communications network.

2) Memory segmentation, the division of computer memory into segments

3) Network segmentation, the splitting of a computer network into sub-networks, each being a network segment or network layer.

4) Image segmentation, the partitioning of a digital image into two or more regions.

5) Speech segmentation, the identification of word boundaries in speech.

6) Text segmentation, the identification of lexical units in writing systems.

c) FRAGMENTATION

In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

d) VIRTUAL MEMORY

In computing, virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage seen by a process or task appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.

e) PAGE TABLE

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM

f) SWAPPING

1)In computer programming, the act of swapping two variables refers to mutually exchanging the values of the variables. Usually, this is done with the data in memory.

2)Replacing one segment of a program in memory (RAM) with another part of the program and restoring it back to the original if required. Exchanging program segments is the primary function of virtual memory, which is a feature in almost every operating system. 

 3) A procedure in which a running program is temporarily suspended and moved onto secondary storage, and primary storageis reassigned to a more pressing job, in order to maximize the efficient use of primary storage.

-LUQMAN-

[Yuganesh]

Paging

Paging is an important part of virtual memory implementation in which the memory is divided into fixed size pages. it is available in the main memory as the OS copies a certain number of pages from your storage device to main memory. 

Segmentation

Segmentation works on segments.A segment is a continuous block of memory of a specific size. 

Fragmentation

refers to condition of disks in which files are divided into pieces scattered around the disk.It often slows down access of data because the disk drive must search through all part of the disks.

Virtual memory

An imaginary memory area which is to  enlarge the address space. Programs use  these virtual adress rather than real addresses to store data. When the program is actually executed , the virtual addresses are  converted into real memory addresses.

Page Table

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses.

Swapping

A dynamic method which involves the transfer processes between memory and disk.What if there is not enough memory to hold all the processes that want to run? The first solution that comes to mind is to move processes that have been blocked or descheduled to disk to make room for other ones that want to run. When it is their turn to run again, they can be brought back into memory.

[Ariel Logujin Takom]

We were asked the following questions on Friday, 8th of August 2014) :

1) What do you know about the following?

a) paging

b) segmentation

c) fragmentation

d) virtual memory

e) page table

f) swapping

a) Paging:

 -> Paging is one of the memory management technique in which the data to be processed are stored in the secondary storage drive (this is usually the Hard Disk Drive [HDD]) so that it can be quickly retrieved and sent to the main memory (RAM) for faster processing. The data stored are usually in same sized blocks called 'pages'. The action of transferring pages from HDD to RAM for processing is what is known as PAGING.

b) Segmentation:

-> Segmentation is the dividing of the computer's PHYSICAL MEMORY to store the address of a data so that when the user prompts the computer to process a certain data, the processor will retrieve the data via the address of the data (called PHYSICAL ADDRESS) stored within the segments or sections of the main memory.

c) Fragmentation:

-> Fragmentation occurs when the storage space of the computer is not being used efficiently, thus causing a drop in capacity and performance of the computer. The basic principle is that as the data is being moved continuously between main memory and the secondary memory, the data, which was initially in the form of 'chunks' are 'shredded' into smaller bits, in which these bits of data are mixed up with other data. Thus, retrieval of the intended data will be hard as the computer needs to recollect all the small bits of the data from all around the secondary memory where the 'shredded' data is stored.

d) Virtual Memory:

-> Virtual memory is a space allocated in the secondary memory to store the data in the form of VIRTUAL ADDRESS. These virtual address is used by the computer to store data/instructions/processes which the computer decides to NOT PROCESS COMPLETELY YET. When the computer does want to completely process them, then this virtual address will be converted into PHYSICAL ADDRESS and sent to the main memory for faster processing via PAGING.

e) Page Table: 
-> Page table is the data structure used in virtual memory to store the MAPPING or CONNECTION between the physical address and virtual address. 

f) Swapping:

-> Swapping is a simple memory management policy in which it moves an entire process between the main memory and the secondary memory.

[Mohd Afif Farhan b. Mat Said]

1. Paging

memory managements schemes of which a computer can retrieve and store data from secondary storage to the main memory in same size blocks called pages.

 

2. Segmentation

division of computer's main memory in segments. A segment is a continuous block of memory of a specific size

Examples:

a) Packet segmentation, the process of dividing a data packet into smaller units for transmission over a data        communications network.

b) Memory segmentation, the division of computer memory into segments

c) Network segmentation, the splitting of a computer network into sub-networks, each being a network segment or network layer.

d) Image segmentation, the partitioning of a digital image into two or more regions.

e) Speech segmentation, the identification of word boundaries in speech.

f) Text segmentation, the identification of lexical units in writing systems.

 

3. Fragmentation

In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

 

4. Virtual memory

virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage as seen by a process or task appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.The primary benefits of virtual memory include freeing applications from having to manage a shared memory space, increased security due to memory isolation, and being able to conceptually use more memory than might be physically available, using the technique of paging.

5. Page Table

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM.

In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. In reality, each process' memory may be dispersed across different areas of physical memory, or may have been moved (paged out) to another storage, typically to a hard disk.When a process requests access to its memory, it is the responsibility of the operating system to map the virtual address provided by the process to the physical address where that memory is stored. The page table is where the operating system stores its mappings of virtual addresses to physical addresses. Each mapping is also known as a page table entry (PTE).

                                          

 6. Swapping       

a) In computer programming, the act of swapping two variables refers to mutually exchanging the values of the variables. Usually, this is done with the data in memory.

b) Replacing one segment of a program in memory (RAM) with another part of the program and restoring it back to the original if required. Exchanging program segments is the primary function of virtual memory, which is a feature in almost every operating system.

 c) A procedure in which a running program is temporarily suspended and moved onto secondary storage, and primary storageis reassigned to a more pressing job, in order to maximize the efficient use of primary storage.

 

[SuhenR]

1) What do you know about the following?
a) Paging
-->Paging is memory managements schemes of which a computer can retrieve and store data from secondary storage to the main memory in same size blocks called pages.
b) Segmentation
--> Memory segmentation is the division of a computer's primary memory into segments or sections. Segments usually correspond to natural divisions of a program such as individual routines or data tables so segmentation is generally more visible to the programmer than paging alone
c) Fragmentation
--> fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. Fragmentation is often accepted in return for improvements in speed or simplicity
d) Virtual Memory
-->Virtual memory is a section of a hard disk that's set up to emulate the computer's RAM. Virtual memory is an imaginary memory area which is to enlarge the address space. It is a memory management technique that uses both hardware and software.
e) Page Table
--> Page table is the data structure used in virtual memory to store the mapping or connection between the physical address and virtual address.
f) Swapping
--> Swapping is a simple memory management policy in which it moves an entire process between the main memory and the secondary memory

[Nabil Izzularif Bin Mohd Safiai]

1. Paging

memory managements schemes of which a computer can retrieve and store data from secondary storage to the main memory in same size blocks called pages.

 

2. Segmentation

division of computer's main memory in segments. A segment is a continuous block of memory of a specific size

Examples:

a) Packet segmentation, the process of dividing a data packet into smaller units for transmission over a data        communications network.

b) Memory segmentation, the division of computer memory into segments

c) Network segmentation, the splitting of a computer network into sub-networks, each being a network segment or network layer.

d) Image segmentation, the partitioning of a digital image into two or more regions.

e) Speech segmentation, the identification of word boundaries in speech.

f) Text segmentation, the identification of lexical units in writing systems.

 

3. Fragmentation

In computer storage, fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

 

4. Virtual memory

virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage as seen by a process or task appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.The primary benefits of virtual memory include freeing applications from having to manage a shared memory space, increased security due to memory isolation, and being able to conceptually use more memory than might be physically available, using the technique of paging.

5. Page Table

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM.

In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. In reality, each process' memory may be dispersed across different areas of physical memory, or may have been moved (paged out) to another storage, typically to a hard disk.When a process requests access to its memory, it is the responsibility of the operating system to map the virtual address provided by the process to the physical address where that memory is stored. The page table is where the operating system stores its mappings of virtual addresses to physical addresses. Each mapping is also known as a page table entry (PTE).

                                          

 6. Swapping       

a) In computer programming, the act of swapping two variables refers to mutually exchanging the values of the variables. Usually, this is done with the data in memory.

b) Replacing one segment of a program in memory (RAM) with another part of the program and restoring it back to the original if required. Exchanging program segments is the primary function of virtual memory, which is a feature in almost every operating system.

 c) A procedure in which a running program is temporarily suspended and moved onto secondary storage, and primary storageis reassigned to a more pressing job, in order to maximize the efficient use of primary storage.

[Megat Muhammad Nasir]

i) Virtual Memory

In computing, virtual memory is a memory managment technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage as seen by a process or task appears as a contiguous address space or collection of continuous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.

ii) Page Table

A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the accessing process, while physical addresses are used by the hardware or more specifically to the RAM.

iii) Fragmentation

Fragmentation is a phenomenon in which storage space is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. For other systems (e.g. the FAT file system) the space used to store given data (e.g. files) is the same regardless of the degree of fragmentation (from none to extreme).

There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity.

iv) Defragmentation

In the maintenance of file systems, defragmentation is a process that reduces the amount of fragmentation. It does this by physically organizing the contents of the mass storage device used to store files into the smallest number of contiguous regions (fragments). It also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmentation utilities try to keep smaller files within a single directory together, as they are often accessed in sequence.

Defragmentation is advantageous and relevant to file systems on electromechanical disk drives. The movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to seek other fragments.

v) Paging

In computer operating systems, paging is one of the memory-management schemes by which a computer can store and retrieve data from secondary storage for use in main memory. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. The main advantage of paging over memory segmentation is that it allows the physical address space of a process to be noncontiguous. Before paging came into use, systems had to fit whole programs into storage contiguously, which caused various storage and fragmentation problems.

Paging is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use secondary storage for data that do not fit into physical random access memory (RAM).

vi) Swapping

(In many programming languages where the swap function is built-in; in C++,overloads are provided allowing std::swap to swap some large structures in O(1) time.) After swap() is performed, x will contain the value 0 and y will contain 1; their values have been exchanged. Of course, this operation may be generalized to other types of values, such as strings, aggregated data types and comparison sorts, utilize swaps to change the positions of data.