We describe the construction of a database of extremely metal-poor ( EMP ) stars in the Galaxy .
Our database contains detailed elemental abundances , reported equivalent widths , atmospheric parameters , photometry , and binarity status , compiled from papers in the literature that report studies of EMP halo stars with \textrm { [ Fe / H ] } \leq - 2.5 .
The compilation procedures for this database have been designed to assemble the data effectively from electronic tables available from online journals .
We have also developed a data retrieval system that enables data searches by various criteria and illustrations to explore relationships between stored variables .
Currently , our sample includes 1212 unique stars ( many of which are studied by more than one group ) with more than 15000 individual reported elemental abundances , covering the relevant papers published by December 2007 .
We discuss the global characteristics of the present database , as revealed by the EMP stars observed to date .
For stars with \textrm { [ Fe / H ] } \leq - 2.5 , the number of giants with reported abundances is larger than that of dwarfs by a factor of two .
The fraction of carbon-rich stars ( among the sample for which the carbon abundance is reported ) amount to \sim 30 % for \textrm { [ Fe / H ] } \leq - 2.5 .
We find that known binaries exhibit different distributions of orbital period , according to whether they are giants or dwarfs , and also as a function of metallicity , although the total sample of such stars is still quite small .