08. Arrays

Arrays :

Arrays are used to store same kind of data in matrix form.

Syntax of array :

    datatype variable_name[No_of_Matrix][No_of_Rows][No_of_columns];
        or
    datatype variable_name[No_of_Matrix][No_of_Rows][No_of_columns] = {value1, value2, value3};

Example :

int main() {
    // 1-D Array
    int marks[100] = {1, 2, 3, 4, 5};

    int length = sizeof(marks) / sizeof(marks[0]);

    // printing elements of array.
    for(int i=0; i<length; i++){
        printf("%d\t",marks[i]);
    }

    return 0;
}

Few important points about arrays :

  1. Indexing of array starts with zero.

  2. Pointer arithmetic is base for indexing of array (discussed in later section).

  3. Arrays follow same naming schemes as variables name.

Types of arrays :

  1. One Dimensional Array

  2. Two Dimensional Array

  3. Three Dimensional Array

One Dimensional Arrays :

One dimensional arrays are used to store multiple columns of data in a single row. * The address of elements inside array is in sequential form. * By default they have few things fixed : * No_of_Matrix = 1, No_of_Rows = 1 * 1-D Array : int age[10];

Syntax of 1-D array:

You could ignore No_of_Matrix and No_of_Rows part, because they are default.

int main() {

    datatype variable_name[No_of_columns];

    or

    datatype variable_name[No_of_columns] = {values};

    return 0;
}

Example of 1-D array :

    int main(int argc, char const *argv[])
    {
        char name[10] = {'J','a','y','a','n','t','\0'};

        printf("first letter : %c\n",name[0]);
        printf("second letter : %c\n",name[1]);
        printf("third letter : %c\n",name[1]);
        printf("fourth letter : %c\n",name[1]);

        // printing via loop
        for(int i=0; i< 10; i++){
            printf("%d | %d\n", i, name[i]);
        }

        return 0;
    }

Memory Representation in case of 1-D :

    name
    {
        [][][][][][][][]        [][][][][][][][]    ........
           1 byte                  1 byte
    }

  1. Here name is main container representing array.

  2. There are sub containers inside name array, 1 byte each representing char datatype.

Two Dimensional Arrays :

Two dimensional arrays are used to store multiple rows and columns of data in a single matrix. * The address of elements inside array is in sequential form. * By default they have few things fixed : * No_of_Matrix = 1, * 2-D Array : int ages[10][10];

Syntax of 2-D array:

    datatype variable_name[No_of_Rows][No_of_columns];
    or
    datatype variable_name[No_of_Rows][No_of_columns] = {values};

Example of 2-D array :

    int main(int argc, char const *argv[])
    {
        char matrix1[2][2] = {{1, 2},{4, 5}};

        // printing via loop
        for(int i=0; i< 2; i++){
            for (int j = 0; j < 2; j++) {
                printf("%d | %d = | %d |\n", i, j, matrix1[i][j]);
            }
        }

        return 0;
    }

Memory Representation in case of 2-D :

matrix

Multi Dimensional Arrays :

Multi dimensional arrays are used to store multiple matrix of data in a sequential order. * Also known as 3 Dimensional Arrays * The address of matrices is in sequential form. * 3-D Array : int ages[2][10][10];

Syntax of 3-D array:

    datatype variable_name[No_of_Matrix][No_of_Rows][No_of_columns];
    or
    datatype variable_name[No_of_Matrix][No_of_Rows][No_of_columns] = {values};

Example of 3-D array:

int main() {
    int data[2][3][3] = {
        {
            {1,2,3},
            {4,5,6},
            {7,8,9}
        },
        {
            {10,11,12},
            {13,14,15},
            {16,17,18}
        }
    };

    printf("Matrix |   Row  | Column =  Value\n");

    //access data using loop.
    for(int matrix=0; matrix < 2; ++matrix){
        for(int row=0; row < 3; ++row){
            for(int col=0; col < 3; ++col){
                printf("%6d | %6d | %6d = %6d\n",
                            matrix, row, col,
                            data[matrix][row][col]);
            }
        }
    }
    return 0;
}

Memory Representation in case of 3-D:

3d-array