FILE ORGANIZATION

Wolmer’s Trust High School for Girls

INFORMATION TECHNOLOGY

 

Grade:  11                                                      Teacher:  Mrs. McCallum-Rodney

 

 

What is a Data File?

A data file is an organized area of memory (disk) that contains information of a similar nature. It is often thought of as a filing cabinet that might contain folders for each of your customers, for example. The filing cabinet is equivalent to the computer data file and the manila folder in the filing cabinet is equivalent to the computer record.

There are two types of files: master files and transaction files.

What is a Master File?

Master files contain the essentially permanent information about customers, inventory items, salesmen, vendors, and general ledger accounts, as well as, other entities.

This is a computer file that is used as the authority in a given job and that is relatively permanent.

 

What is a Transaction File?

The transaction files contain more changeable things such as sales orders, purchase orders, cash receipts, and accounts payable invoices--things that are constantly changing from day to day.

This is a computer file containing relatively temporary data about a particular data processing task.

 

What is a database? 

 

Often abbreviated DB. A collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system.

 

What is a field?

 

A space allocated for a particular item of information. A tax form, for example, contains a number of fields: one for your name, one for your Social Security number, one for your income, and so on. In database systems, fields are the smallest units of information you can access. In spreadsheets, fields are called cells.

 

Most fields have certain attributes associated with them. For example, some fields are numeric whereas others are textual, some are long, while others are short. In addition, every field has a name, called the field name.

What is a record?

A collection of fields is called a record.

 

What is disk defragmentation?

 

This is the process of reorganising a disk so that the files are stored in contiguous (side-by-side) sectors, thus speeding up the disk access and the performance of the entire computer.

 

How does disk defrag work?

 

The word "disk defrag" is typically used to refer to the Microsoft Windows utility called Disk Defragmenter. It is designed to solve a problem that occurs because of the way hard disks store data.

There are three key facts about hard disks:

1.Hard disks store data in chunks called sectors. If you imagine the surface of the disk divided into rings (like the rings of a tree), and then imagine dividing each ring into pie-slices, a sector is one pie-slice on one ring. Each sector holds a fixed amount of data, like 512 bytes.

2.The hard disk has a small arm that can move from ring to ring on the surface of the disk. To reach a particular sector, the hard disk moves the arm to the right ring and waits for the sector to spin into position.

3.Hard disks are slow in computer terms. Compared to the speed of the processor and its memory, the time it takes for the arm to move and for a sector to spin into place is an eon.

Because of fact #3, you want to minimize arm movement as much as possible, and you want data stored in sequential segments on the disk.

So let's imagine that you install a new application onto an empty hard disk. Because the disk is empty, the computer can store the files of the application into sequential sectors on sequential rings. This is an efficient way to place data on a hard disk.

As you use a disk, however, this efficient technique becomes harder for a disk. What happens is that the disk fills up. Then you erase files to reclaim space. These files that you delete are scattered all over the surface of the disk. When you load a new application or a large file onto the disk, it ends up being stored in hundreds or thousands of these scattered pockets of space. Now when the computer tries to load the scattered pieces, the disk's arm has to move all over the surface and it takes forever.

The idea behind the disk defragmenter is to move all the files around so that every file is stored on sequential sectors on sequential rings of the disk. In addition, a good defragmenter may also try to optimize things even more, for example by placing all applications "close" to the operating system on the disk to minimize movement when an application loads. When done well on older disks, defragmenting can significantly increase the speed of file loading. On a new disk that has never filled up or had any significant number of file deletions, it will have almost no effect because everything is stored sequentially already.

As you might imagine, the process of individually picking up and moving thousands of files on a relatively slow hard disk is not a quick process -- it normally takes hours.

Starting with Windows 98, the defragmenter places the data on the hard drive in the same sequence Windows uses it. The Windows 98 defragmenter also knows what programs you run the most often, and places those on the disk so the computer can access it the fastest possible time

 

Formatting a disk

 

Disk formatting is the process of preparing a hard disk or other storage medium for use, including setting up an empty file system.

A corrupted operating system can be reverted to a clean state by formatting the hard disks into partitions that are divided into logical sections that are formatted with their own file systems. This is normally only done on hard disks because of the small sizes of other disk types, as well as compatibility issues.

A corrupted operating system can be reverted to a clean state by formatting the disk and reinstalling the OS, as a drastic way of combating a software problem or malware infection. Obviously, important files should be backed up beforehand.

BACKING UP A FILE

It is necessary to have a backup of your complete hard disk including every aspect of the installed operating systems, which you can restore if you have to replace your hard disk or if you screw things up.

COMPRESSING A FILE

A compression of a file is to save space on a storage medium.

CONVERSION TO A NEW SYSTEM

When a new system needs to be implemented in an organization, there are three different ways to adopt this new system: The big bang adoption, phased adoption and parallel adoption. In case of parallel adoption the old and the new system are running parallel, so all the users can get used to the new system, and meanwhile do their work using the old system. Phased adoption means that the adoption will happen in several phases, so after each phase the system is a little nearer to be fully adopted.

Note:  With a pilot conversion only one location in the company uses the new system – so it can be tested.  After the pilot site approves the new system, other sites convert using one of the other conversion strategies.

PARALLEL CONVERSION FROM AN OLD SYSTEM TO A NEW SYSTEM

Parallel adoption is a method for transferring between an old (IT) system to a target (IT) system in an organization. In order to reduce risk, the old and new system run simultaneously for some period of time after which, if the criteria for the new system are met, the old system is disabled. The process requires careful planning and control and a significant investment in labor hours.

DIRECT CONVERSION FROM AN OLD SYSTEM TO A NEW SYSTEM

This is the adoption type of the instant changeover, when everybody trained to use the  new system moves to the fully functioning new system on a given date.

·         At a  predetermined time the old system will no longer be used and learning will occur via the new system

·         Useful in a scenario like a school wins a contract to deliver existing learning to a group of students overseas.  The new system has to be ready next January to deliver to these new clients as well as the local clients.

With the big bang adoption, the switch between using the old system and using the new system happens at one single date, the so called instant changeover of the system. Everybody starts to use the new system at the same date and the old system will not be used anymore from that moment on.

The big bang adoption type is riskier than other adoption types because there are fewer learning opportunities incorporated in the approach, so quite some preparation is needed to get to the big bang. 

The advantages of this method:

·         Training is only needed for the new system.

·         User documentation does not need to be updated during the implementation process, because it happens in such a short period.

·         The changeover is at one date and this date is clear for everyone.

·         There are no special interfaces needed to be able to get used to the new system, because the new system is all there is.

The disadvantages on the other hand are:

·         There is no time for extra additions

·         The completeness and validity of the converted data is not completely proved, only in the pre-phases, but not in the whole system situation.

·         Start up problems are a problematic factor

·         The operation is complex, one of the main complexities is tuning all activities to happen on one moment: the big bang

·         ‘Fall back’-plans are hard to develop and become more impossible when the big bang has taken place

·         This adoption is vulnerable because of the limited possibilities to maneuver. There is a lot of pressure because the deadline must be met.

PHASED CONVERSION

The new learning system is introduced a section/unit at a time.  The remaining units are delivered using the old system.

Pros:

·                     The conversion will be done in parts. Time is available for adjustments

·                     Negative influences that arise at the start are less critical

·                     No ‘catch-up’ period is needed.

·                     Time for the users to adapt is longer

·                     Technical staff can concentrate on part of the system or some of the users.

Cons:

·         Several adjustments are needed

·         Training sessions are confusing for users as they are asked to work with the new and the old system

·         Several changes in documentation

·         The duration of the project

·         System delivery milestone is unclear

·         Correctness and completeness of the dataset has to be checked several times

·         A ‘fall back’ to the old system is becoming more difficult with every new phase.

·         The implementation may appear unclear to the employees and other users.

Risks:

·                     Complexity of the implementation

·                     Prone to make mistakes

·                     Fall back impossible in later phases