Ruby/CArray is an extension library for the multi-dimensional numerical array class. CArray can store integers and floating point numbers to perform calculations efficiently. Therefore, Ruby/CArray is suitable for numerical computation and data analysis. Ruby/CArray has different features from other multidimensional array libraries (narray, numo-narray, nmatrix), such as element-wise masks, creation of reference arrays that can reflect changes to the referent, the ability to access memory pointers of other objects, user-defined arrays, and so on.