Blog - DATA SCIENCE

Tree indexing

In the indexed files seen in previous posts, the table of indexes is accessed sequentially with the drawbacks that I already mentioned this type of access has. However, there is a much more efficient indexing technique than sequential indexing and that is tree indexing, which significantly reduces search time. In this post, I will explain the aforementioned technique.

Using sequential access, when looking for data, it has to go through the index file sequentially until we find the searched one, obtaining the memory address of the beginning of the record in the data file. As index tables are much less heavy than files with all the data, we have a considerable improvement using indexes, even if the search in the table for these is sequential.

By changing the index table of sequential access to an organization of the indexes in a data tree, it will be able to access the indexes much more quickly. These types of structures are specially indicated to speed up searches, but let’s see how it does.

Indexed access

After the random access files I explained in the previous post, indexed access appears to correct the main drawbacks of those. Random access files meant a considerable reduction in the search time of data compared with the sequential access files. However, you had to know exactly the registration number of the data you are looking for, which is far to be efficient, since normally we will want to search by values in the different fields.

Let’s see it with our character Antonio, who changed from sequential access files to random access files. It turns out that when searching for a supplier by the registration number, he is wrong many times as he hardly remembers the position of this supplier in the file. He would like to be able to search for the supplier’s data, by the name of the supplier or by the name of the contact, but doing by the registration number of the suppliers usually ended making a mistake.

Random access files

Random access files allow us to go directly to recover the desired record, without having to read all the previous ones before. In this way they solve the main limitation of sequential access files, which was precisely their method of accessing the data, the need to go through the entire file from the beginning until we reached the point that interested us. This limitation is high time consuming and became larger and larger as the size of our file increases. Working with sequential access files having a high number of records, the reading times could take too long, to the point of not being operative and making sense of a migration to a random access file.

Sequential access files

Sequential access files were the first digital storage solution, those files present a certain structure to store the data but are still far away from the databases.

Let’s put ourselves at the beginning of the second half of the twentieth century when our protagonist Antonio begins to digitally the data of his business, the SuperGades store. The option available then was simply to pass the data from a paper file to a digital file, using a very simple word processor with very few functionalities, in which we would write the data without any format. This file is also called an archive, taking the name of its analogue antecedent, a physical file with drawers where we kept the files with the data.

Data organization

Organizations have always had to save and process different data for their operation. Data organization for its subsequent analysis has been one of the priorities for the organizations. Many years ago, computers were not available yet, the data was recorded on paper and stored in filing cabinets. Physical cabinets with drawers, which we consulted when we needed to recover any of these data.

This data organization forced us to have large spaces for storage and required a great effort of registration. It also had many other drawbacks. Always we wanted to access a piece of data, it spent considerable time locating it. Access was exclusive so that if someone was consulting any file of information, it was not available to anyone else. All this without mentioning the limited possibilities available for data processing.

The power supply

All the devices connected to the motherboard, need to be supplied with the electrical current for their operation. The power supply is the component of the computer that fulfils this function.

We take the electrical current from the electric supply network, to which we plug the PC Power Supply, which transforms alternating current into direct current, at suitable voltages for the computer devices. Therefore, although we normally refer to the Power Supply with that name, it does not generate electricity, it is not a source, but a transformer from alternating current to direct current, and from high voltage to low voltage.

Usually, a computer needs a 12-volt direct current to power the motors of devices, such as hard drives, and a 5-volt or 3.3-volt direct current for the different electronic components.

The motherboard

When we open a computer and look inside, it is inevitable to be surprised by the motherboard. The amount and variety of components can scare us a little, but in this post, we are going to analyze them and take away some basic ideas that will help us in our understanding of motherboards. In any event, first thing is to understand what the motherboard is and what it is for.

The motherboard is the integrated circuit that connects all the components of the computer. Some of them will be directly soldered to the plate. Others, such as the CPU or RAM, are connected through dedicated connectors. And the rest they do it through the so-called expansion buses (internal ports) or through the external ports.

Components of the computer

In previous posts, I have given a small introduction about the computer and its evolution, as a general purpose machine, and some basic brushstrokes about its architecture. The next posts will deal in detail with the different components of the computer, but before that, I think it will help to make a small list with these components, so that the student can get an idea of what is to come.

The architecture of computers

Talking about the architecture of computers, we refer to the set of all the blocks (one or several components) and the communications between them, which make the computer work in a coordinated way, serving a common purpose. Each block fulfills one or more tasks, which orderly and coordinated contribution makes the computer fulfills the function for which it was designed.

Classifying computers

We have a natural tendency to pigeonhole and classify things, and computers are not an exception. In this post, we are going to see the most common way of Classifying computers.

If we wonder what type of computer our laptop is, you might think that it fits perfectly into the category of minicomputer however it isn´t, it is really a microcomputer. But how important is this for me? What matters if my laptop is a minicomputer or a microcomputer? Well, even if you are never going to work with another computer than your laptop, it is always good to know that there are other categories of computers with other features, many more than those of your laptop. Who knows, maybe on some occasion you will have to face some task too big for your laptop.

The most common way to classify computers is according to their performance. We distinguish 5 types or categories.