Help with writing a new moving average

[Ka Ho]

Hello,

I am very new here  and want to practice a bit in coding. I decided to write a moving average.

Writing from scratch is hard so I pull up an ema script people writes.

There is this line

inpPrice = PRICE_CLOSE

_ema.calculate()

getPrice(inpPrice,open,high,low,close,i)

I would like to know what 

_ema.calculate()

getPrice()

do, why don't we just use open high low and close themselves to calculate?

Let say I want to manipulate the open high low and close before feeding into the moving average function, can I just change the arguments in getPrice(inpPrice,open,high,low,close,i)?

Here is the ema code I found online:

https://www.mql5.com/en/code/25047