Array is a data structure used to store a set of values (different types). There are two categories or arrays : One-dimensional and Multi-dimensional arrays.

Array and variable representation in memory (codeforwin.org)

//Syntax: 
dataType arrayName[arraySize];
// Examples: 
int data[100]; // 100 integers
float data[5]; // 5 floating-point values
// Note
// The size and type of an array cannot be changed once it is declared.

// Other declation forms 1
int data[5] = {19, 10, 8, 17, 9};
int data[] = {19, 10, 8, 17, 9};

// Other declation forms 2
int n = 10; 
int data[n];

// Other declation forms 3 (rest two elements as 0)
int arr[6] = { 10, 20, 30, 40 } -> int arr[] = {10, 20, 30, 40, 0, 0}

Accessing Array Elements (geeksforgeeks.org)

int data[5] = {19, 10, 8, 17, 9};
printf("%d %d", data[0], data[1]); --> 19 10

// Changing the value of the third element to -1
data[2] = -1;

// take input and store it in the 3rd element
​scanf("%d", &data[2]);

// in a loop
for(int i = 0; i < 5; ++i) {
     printf("%d\\n", data[i]);
}