[Solved]I really need a little bit explain on parameter for function (Please HELP meTwT)

Question

Can someone help me explain why While(StockSelect(stocknum)) need to have 'stocknum' in the parameter of the function 'StockSelect' as it didn't get any input value yet or is there any reasons for doing this?
#My teacher show me this example code for my project
#Thanks for your answer

int main()
{
int stocknum;
while(StockSelect(stocknum))
{
int inqchoice = ShowStockMenu();
switch(inqchoice)
{
case 1:
PriceDataInquiry(stocknum);
break;
case 2:
GainLossCalculation(stocknum);
break;
default:
cerr<<"Invalid inquiry choice!"<<endl;
exit(EXIT_FAILURE);
}
}
return 0;
}

Answer 1

~ swim ~ That's what I needed! Thank you!

Answer 2

Martin Taylor Thank you I will go read some more:3