The diary is not written in the classic forms of "Dear Diary" or as letters to oneself; Anne calls her diary "Kitty", so almost all of the letters are written to Kitty. Anne used the above-mentioned names for her annex-mates in the first volume, from September 25, 1942 until November 13, 1942, when the first notebook ends. It is believed that these names were taken from characters found in a series of popular Dutch books written by Cissy van Marxveldt.
Anne's already budding literary ambitions were galvanized on 29 March 1944 when she heard a London radio broadcast made by the exiled Dutch Minister for Education, Art, and Science, Gerrit Bolkestein, calling for the preservation of "ordinary documents—a diary, letters ... simple everyday material" to create an archive for posterity as testimony to the suffering of civilians during the Nazi occupation. On May 20, 1944, she notes that she started re-drafting her diary with future readers in mind. She expanded entries and standardized them by addressing all of them to Kitty, clarified situations, prepared a list of pseudonyms, and cut scenes she thought would be of little interest or too intimate for general consumption. By the time she started the second existing volume, she was writing only to Kitty.