Title of program: TOROID Method of solution Catalogue number: AAAE The structure problem is mathematically a boundary-value problem for a second-order, non-linear, two-dimensional partial Program obtainable from: CPC Program Library, Queen's Uni-differential equation. This problem is solved numerically by versity of Belfast, N. Ireland (see application form in this issue) following Stoeckly's method [2] improved by Miketinac and Computer: UNIVAC 1106; Installation: Computer Centre, Barton [31,who used it to calculate post-newtonian corrections University ofCape Town to the equilibrium configurations of rotating polytropes. Operating system: Exec 8 Restrictions on the complexity of the problem Programming language used: Fortran y The mathematical method adopted in developing the program works only for polytropes whose polytropic index is greater High speed storage required: 43K words. than or equal to one, [2]. However, in addition to calculating No. of bits in a word: 36 equilibrium configurations of polytropes pervaded by toroidal Overlay structure: Overlaid magnetic fields, the program, with minor modifications, could also be used for calculating equilibrium configurations of (uni-No. of magnetic tapes required: None formly or non-uniformly) rotating polytropes or rotating poly-Other peripherals used: Card reader, line printer tropes pervaded by toroidal magnetic fields or (rotating) poly-No. of cards in combined program and test deck: 1652 tropes containing toroidal magnetic fields of the type other than the one considered in [1]. The ratio of the specific heats, Card punching code: EBCDIC '~',can be any number.