Diana Merry-Shapiro was a computer programmer for the Learning Research Group of Xerox PARC in the 1970s and 1980s, after having originally been hired as a secretary. As one of the original developers of the Smalltalk programming language, she wrote the first system for overlapping display windows. Merry was also one of the co-inventors of the BitBLT ('bit block transfer') routines for Smalltalk, subroutines for performing computer graphics operations quickly which were pivotal in the evolution of user interfaces from text-based computing to graphical user interfaces.
As of 2003, Merry-Shapiro was still using Smalltalk as an employee of Suite LLC, a financial consulting firm.