Q:

Initialize array in c in the format `int a[3]={0,};`

I had seen a source where array initialize in int arr[3] ={0,}; What does it mean ? I normally use this format int arr[3]={0}; can i know what is the difference 

A:

This is probably a dup, but I'll take a shot anyhow.
There is no difference between   int arr[3] ={0,};  and   int arr[3] ={0};. 
Ref: C11 6.7.9:
    initializer:
         assignment-expression
         { initializer-list }
         { initializer-list , }

Both forms of initializer lists are considered initializers.  The form with the comma at the end is preferred by many because it makes it easier to rearrange or add elements to the list during code maintenance. 
 int arr[3] ={0,}; 

declares an array of three elements and initializes the first element to 0. When you do a partial initialization, the rest of the array is automatically initialized with zeros. 
Ref. C11 6.7.9:

If there are fewer initializers in a brace-enclosed list than there
  are elements or members of an aggregate, or fewer characters in a
  string literal used to initialize an array of known size than there
  are elements in the array, the remainder of the aggregate shall be
  initialized implicitly the same as objects that have static storage
  duration.

