Alonzo Church (1903–1995) was an American mathematician and logician who made significant contributions to mathematical logic and the foundations of computer science. He is best known for the development of lambda calculus, a formal system that became a fundamental concept in the theory of computation. Here are key aspects of Alonzo Church’s life and work:

1. Early Life and Education:
   • Alonzo Church was born on June 14, 1903, in Washington, D.C., United States.
   • He earned his Ph.D. in mathematics from Princeton University in 1927 under the supervision of Oswald Veblen.
2. Lambda Calculus:
   • Church introduced lambda calculus in the 1930s as a formal system for representing computation. Lambda calculus is a mathematical abstraction used to study the concept of computability and is considered one of the foundational elements of computer science.
3. Church-Turing Thesis:
   • Church independently formulated the Church-Turing thesis, which posits that any effectively calculable function can be computed by a Turing machine. This thesis played a crucial role in shaping the understanding of computability and the limits of what can be algorithmically computed.
4. Contributions to Logic:
   • Church made significant contributions to mathematical logic. He worked on the development of the lambda calculus as a foundation for logic and computation.
   • His work on the concept of effective calculability, along with Turing’s work on Turing machines, laid the groundwork for the Church-Turing thesis.
5. Collaboration with Alan Turing:
   • Church and Alan Turing independently developed similar concepts of computability around the same time. They later corresponded and recognized the equivalence of their approaches, contributing to the formulation of the Church-Turing thesis.
6. Introduction of Church Numerals:
   • Church introduced Church numerals, a way of representing natural numbers using lambda calculus. Church numerals are part of the encoding of data within the lambda calculus.
7. Academic Positions:
   • Church held academic positions at various institutions, including Princeton University and the University of California, Los Angeles (UCLA).
   • He was a professor at Princeton for many years and had a significant influence on generations of mathematicians and computer scientists.
8. Church-Rosser Theorem:
   • Church proved the Church-Rosser theorem, which is a fundamental result in lambda calculus. The theorem asserts that, in a specific formal system, if two reduction sequences start from the same term, they can be joined to a common reduction sequence.
9. Later Life:
   • In the later part of his career, Church continued to contribute to logic and the foundations of mathematics.
   • He also served as the editor of the Journal of Symbolic Logic for many years.
10. Death:
    • Alonzo Church passed away on August 11, 1995, in Hudson, Ohio, United States.

Alonzo Church’s work laid the theoretical groundwork for the field of computer science. His development of lambda calculus and the Church-Turing thesis provided key insights into the nature of computation and played a crucial role in the development of the theory of algorithms and computability.