IT PhD Computer Journal

1. Install MinGW (how to set up MinGW – watch this video)
2. Inatsll Visual Studio Code (VSC)
3. you can immediately integrate VSC with Git so that everything is automatically synchronized. To do this, simply make a repository on Github and clone it to some folder on your computer. Open this folder in VSC and it will automatically pick up this repository, suggesting synchronization 🙂 Agree, what is already there. You can commit through the button in VSC (see the screenshot on the right) or automatically.
4. now install the plugin there “C/C++ for Visual Studio Code”:

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At the end of the fifth week of the CS50 Harvard course, we studied hash tables, which can be used to solve the problem of hashing words from text to check their spelling in a dictionary (speller.c). A dictionary is given in which words are listed on each new line. In a separate file, the text is given, which the program must check – which words in the text are spelled incorrectly. It is believed that all words that are not in the dictionary are wrong words.

It is necessary not only to create a program code that checks words from the text with a dictionary, but also to minimize the speed of this program. In order for the program to work quickly, you need to come up with your own hash function and choose the optimal number of buckets in the hash table (26 buckets are initially suggested). The task is located in the dictionary file (dictionary.c) and consists of four functions: dictionary loading (load), hash function (hash), word check (check) and memory release (unload).

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In the fifth week of the Computer Science – CS50 (Harvard) course, we studied data structures and learned how to access structure elements by their address. To complete your homework (Lab 5 – inheritance.c), you need to understand the scientific principle of inheritance of blood type from parents to children. Challenge: Write a program that runs a simulation of a three-generation family and assigns each member a blood type based on the parent’s blood type.

How blood type is inherited:

• there are only three possible forms of the gene (they are called the “allele” or building block) that determine the type of blood group – these are A, B, and O;
  the blood type itself is always two alleles (all sorts of combinations of A, B, and O), for example, AO, AA, OB, etc.;
• the blood type is “transmitted” from parents to the child as follows: one allele is randomly selected from each parent and then they are combined into a new pair – this is the child’s blood type (for example, the parents had AO and OB -> the child may have AB , OO, OB or AO).

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Random number generator in C with srand() and time(). Srand() is a helper function for the rand() function, generating a seed for the start of a sequence of (pseudo)random numbers. Because the time returned by the time() function changes once a second, when calling this code more often, there will be no randomness. To be – use nanoseconds through timespec_get ().

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
    int n, r;

    printf("Rng at your service:\n\n");
    srand((unsigned)time(NULL));

    for (n = 0; n < 10; n++)
    {
            r = rand();
            printf("%d\t", r % 100);
    }

    return 0;
}

Imagine that you deleted photos from your memory card and then wanted to restore them. It turns out that in some cases it is possible to do this, because when we delete a photo with the “delete” button, what actually happens is more like not deleting, but forgetting. The links between the bytes are lost, but the information itself is still in memory until it is overwritten with new photographs. Passing the CS50 course (Harvard) – at the end of the fourth week, we got the recover.c task, in which we are given the source file of the memory card card.raw and need to write a program that will restore all the photos.

Digital cameras often store photographs one after another in accordance with the FAT file system, where all information is divided into blocks of the same size of 512 bytes. And each photo is recorded using these blocks. Considering that photos can differ slightly in size from each other, but at the same time be recorded in the same number of blocks, it allows you to write code that sequentially goes through each block of the card’s memory and copies this data into new files. The “extra” bytes are called “unallocated space”, and even ancient photographs can be stored in it.

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At the end of the fourth week of the CS50 (Harvard) course, we had an interesting task: to make a program that takes the original image and imposes a filter on it with selection of the edges of objects (filter-more). This effect is achieved by applying the Sobel operator – a 3×3 grid is taken around each source pixel (another 8 pixels, in addition to the source one) and calculated by the formula, first the Gx and Gy values, and then the square root is calculated from the sum of the squares of the obtained values. The Gx and Gy values ​​are squared to avoid negative numbers.

What is the square of the numbers Gx and Gy? This is the calculation of the vertical and horizontal derivative values, which in practice looks like multiplying the RGB color values ​​of each pixel by a number in the given Gx and Gy matrices. The essence of such calculations is that we compare the values ​​​​on each side of zero, if there is no difference, then the color does not change, if there is a transition from smaller to larger, then there is a gradient and the larger the difference, the more the color changes in the image . Therefore, in the place where there is a transition, a “border” will be drawn on the new image.

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