Another difficulty of programming the Ferranti Mark 1 computers was the two-level storage of the computers. There were eight pages of Williams cathode ray tube (CRT) random access memory as the fast primary store, and 512 pages of the secondary store on a magnetic drum. Each page consisted of thirty-two 40-bit words, which appeared as sixty-four 20-bit lines on the CRTs. The programmer had to control all transfers between electronic and magnetic storage, and the transfers were slow and had to be reduced to a minimum. For programs dealing with large chunks of data, such as matrices, partitioning the data into page-sized chunks could be troublesome.