Dewar, born in Oxford, England, earned his bachelor's degree and Ph.D. from the University of Chicago. He later joined the Computer Science faculty at New York University (NYU), where he became a full professor, and eventually served as chair of the department.
Specializing in programming language design and implementation, Dewar participated in the SETL project and became involved with Ada from the outset, first as a consultant to one of the language design teams and subsequently as a Distinguished Reviewer. He was one of the architects of the Ada/Ed compiler at NYU, which was written in SETL and served as an operational definition of the Ada 83 language. He was actively involved with Ada throughout the language’s history, as a member of the Ada Rapporteur Group that maintains the language standard and as a designer and implementor of AdaCore's GNAT Ada technology.
Dewar also was involved in the design of Algol 68, was a member of IFIP WG2.1 on Algorithmic Languages and Calculi, and served as that group's chair from 1978 to 1983. He was an expert in all aspects of language technology and co-developed compilers for SPITBOL (SNOBOL), Realia COBOL for the PC, and Alsys Ada. He also designed and implemented several real-time operating systems for Honeywell Inc.
In addition to co-authoring several books and writing many articles and technical papers, Dewar was a recognized expert in copyright and patent law for software.
At AdaCore, "the leading provider of commercial software solutions for Ada," Dewar was active in all phases of the company’s business. He was principal architect of the GNAT compiler technology, a member of several product development teams, tracked problem reports to make sure they were handled properly, wrote numerous journal articles and opinion pieces on topical events in the industry, and served as company spokesman to customers and the trade press. He was an outspoken advocate of Freely Licensed Open Source Software, and was instrumental in establishing a cooperative relationship between AdaCore and the Free Software Foundation.
David Cook, chair of ACM's Special Interest Group on Ada (SIGAda), said, " I personally compiled my very first Ada program in a workshop that Robert taught. Robert's passing leaves a void in the entire computing community, and especially in the Ada world."
Dewar is survived by two children, Jennifer and Keith Dewar, and two grandchildren.