He was born in 1951 in Cluj, in the Transylvania region of Romania, the son of Ilie and Rafila Cristian.
After graduating from the Nicolae Bălcescu High School in his native city, he went in 1971 to France to study at the Grenoble Institute of Technology, in the Department of Applied Mathematics and Computer Science.
[1][2] Cristian went on to the University of Newcastle upon Tyne in the United Kingdom, where he worked in the area of specification, design, and verification of fault-tolerant software.
In 1982 he emigrated to the United States, joining the IBM Research Center in Almaden Valley, in San Jose, California.
[2] In 1991 he joined the University of California, San Diego as Professor in the Department of Computer Science and Engineering.