Exponential Integral Ei(x)

TOMS385 is a FORTRAN77 library which implements ACM TOMS algorithm 385, for evaluating the exponential integral Ei(x).

The text of many ACM TOMS algorithms is available online through ACM: or NETLIB:


TOMS385 is available in a FORTRAN77 version.

Related Data and Programs:

TEST_VALUES, a FORTRAN77 library which supplies test values of various mathematical functions.


  1. Kathleen Paciorek,
    Algorithm 385: Exponential Integral Ei(x),
    Communications of the ACM,
    Volume 13, Number 7, July 1970, pages 446-447.

Source Code:

Examples and Tests:

List of Routines:

You can go up one level to the FORTRAN77 source codes.

Last revised on 10 January 2006.