Memset statement doubt

#1

What does the memset statement do? And second question, why is “a” and “pre” pre-defined?

#2

memset is used for initializing array with given value.
pre[ ] is used to store the % values of sum, and a[ ] is array of given elements.

#3

Why are we using memset? It uses header we are dealing with integers over here.

#4

@yobasu2015 memset(array_name,value,sizeof(array_name)) is syntax for using memset.
it initializes every element of array_name with value.