Carlos was born in Pawtucket, Rhode Island, the first of two children born to working-class parents. Her mother played the piano and sang and had an uncle who played the trombone and another who played the trumpet and drums. She began piano lessons at six years of age, and wrote her first composition, "A Trio for Clarinet, Accordion, and Piano," at 10. Carlos attended St. Raphael Academy, a Catholic high school in Pawtucket. In 1953, at fourteen, Carlos won a scholarship for building a computer presented at the Westinghouse Science Fair, a science competition for high-school students. From 1958 to 1962, Carlos studied at Brown University and graduated with a degree in music and physics, during which she taught lessons in electronic music at informal sessions.