The C Programming Language

For Your Amusement " C is quirky, flawed, and an enormous success. While accidents of history surely helped, it evidently satisfied a need for a system implementation language efficient enough to displace assembly language, yet sufficiently abstract and fluent to describe algorithms and interactions in a wide variety of environments. "-Dennis Ritchie 2 Goals of this Lecture Help you learn about: • The decisions that were made by the designers* of C • Why they made those decisions … and thereby… • The fundamentals of C Why? • Learning the design rationale of the C language provides a richer understanding of C itself • A power programmer knows both the programming language and its design rationale * Dennis Ritchie, then later, members of standardization committees 3 Historical context-1972 Operating systems were programmed in assembly language (i.e., in machine instructions) [Efficient; expressive; easy to translate to machine language; but not portable from one computer instruction set to another; hard to write programs, hard to debug, maintain…] Application programs were in " high-level " languages such as Need: ease of programming, (reasonable) expressiveness, structured programming, data structures, modularity, compilable on a 64-kilobyte computer Program operating-systems in a " high-level " language Don't even attempt: safety When possible, have a bit of: portability Goals for Java language-1995 It's not that Java was particularly innovative (in these respects). By 1995, decades of computer-science research had made it straightforward to achieve all these goals at once. In 1972, nobody knew how.