any one why we call the functions and what its advantage

Answer 1

You call a function when you want to do some specific work.
So, instead of typing the same text (telling it what to do) again and again, the programmer can type it once and call it wherever required.

Answer 2

for exemple if you need to calculate a max of 4 number with function you write :
X = max (max(a,b),max(c,b));
without use function : it's too long . try it

Answer 3

after creating function we can call it number of time and that will reduce time and space complexity for code ....main advantage is according to need and functionality we can use use it....