Rounding up and down a number C++

Question

I'm trying to allow my program to round a number up and down respectively.

For example, if the number is 3.6, my program is suppose to round up the nearest number which is 4 and if the number is 3.4, it will be rounded down to 3.

I tried using the ceil library to get the average of 3 items.

results = ceil((marks1 + marks2 + marks3)/3)

However, the ceil only rounds the number down but does not roll the number up.

There's 1 algorithm i stumbled upon

var roundedVal = Math.round(origVal*20)/20;

but i still can't figure a formula for some problem.

Answer 1

std::ceil 

rounds up to the nearest integer

std::floor 

rounds down to the nearest integer

std::round 

performs the behavior you expect

please give a use case with numbers if this does not provide you with what you need!