Some of your code statements are very long and you'd like to make them more readable by splitting them over multiple lines.
Use the underscore character (_) to break statements over multiple lines, as shown in Example 2-10.
Example 2-10. Spanning multiple lines
k2(1) = dt * dy1dt(y(1) + k1(1) / 2#, y(2) + _ k1(2) / 2#, y(3) + k1(3) / 2#, y(4) + _ k1(4) / 2#)
You must include a space between the last character of a line and the underscore character.