Working out the function round(5.879) gives the value 6 or 'returns' the value 6.
Functions that return values can form part of expressions. Using 'x <- pow(3,2)+round(5.879)' in a flowchart would therefore assign the value 15 to the variable x.
Sometimes a function can return a value even if it does not have any parameters. For instance, the function rand() returns a random number between 0 and 1 whenever it is called. It needs no parameters to do this.