The data ﬁles used by Matpower are Matlab M-ﬁles or MAT-ﬁles which deﬁne and return a single Matlab struct. The M-ﬁle format is plain text that can be edited using any standard text editor. The ﬁelds of the struct are baseMVA, bus, branch, gen and optionally gencost, where baseMVA is a scalar and the rest are matrices. In the matrices, each row corresponds to a single bus, branch, or generator. The columns are similar to the columns in the standard IEEE CDF and PTI formats. The number of rows in bus, branch and gen are , and , respectively. If present, gencost has either or rows, depending on whether it includes costs for reactive power or just real power. Full details of the Matpower case format are documented in Appendix B and can be accessed from the Matlab command line by typing help caseformat.