Awk command - calculation of columns

Question

I am very new in Awk. I want to calculate the difference between first row column2 and second row column2. For instance:

Num1 Num2 
23   26
34   39
43   58
63           


        

Answer 1

Remember the old values (from the previous row).

awk 'NR > 1 { print $1 - old1, $2 - old2 }
            { old1 = $1; old2 = $2 }' data.file