An array in C is initialized by assigning values to its elements at the time of declaration using an initializer list enclosed in curly braces {}. Here are the common ways to initialize an array in C:

• Initialize with all elements specified:
  You can declare and initialize an array by listing all its elements inside braces. For example:

  c
  
  int arr[] = {1, 2, 3, 4, 5};
  

This creates an array of size 5 with values 1, 2, 3, 4, and 5 in order

• Partial initialization:
  You can initialize only some elements, and the rest will be set to zero automatically if the array has static storage duration or if partially initialized. For example:

  c
  
  int arr[5] = {1, 2, 3};
  

Here, arr = 1, arr[1] = 2, arr[2] = 3, and the remaining elements are initialized to 0

• Omitting the size:
  When you provide an initializer list without specifying the size, the compiler infers the size from the number of elements in the list:

  c
  
  int arr[] = {10, 20, 30};
  

This creates an array of size 3

• Initialize all elements to zero:
  You can initialize all elements to zero by using {0}:

  c
  
  int arr[5] = {0};
  

This sets all 5 elements to zero

• Using loops for initialization:
  Arrays can also be initialized element-by-element in a loop after declaration:

  c
  
  int arr[5];
  for (int i = 0; i < 5; i++) {
      arr[i] = i * 2;
  }
  

This sets elements to 0, 2, 4, 6, 8 respectively

Summary of Syntax

c

// Declare and initialize with explicit size
int arr[5] = {1, 2, 3, 4, 5};

// Declare and initialize without size (size inferred)
int arr[] = {1, 2, 3};

// Partial initialization, rest zero
int arr[5] = {1, 2, 3};

// Initialize all to zero
int arr[5] = {0};

In all cases, the initializer list is a comma-separated list of constant expressions inside braces {} and is preceded by an equal sign =

. This is the standard and most common way to initialize arrays in C.