Why Can’t Johnny and Jenny Program in C?

1. Why Can’t Johnny and Jenny Program in C? (and why their parents could) Eric Freudenthal <efreudenthal@utep.edu>, Brian A. Carter, Alexandria N. Ogrey <{bacarter,anogrey}@miners.utep.edu> What Changed Observations Hypotheses • OO-programming and machine organization taught separately. • Semantics of Procedural langauges are more similar to underlying hardware than OO languages. • C introduced in a language survey course where semantics are disconnected from implementation. • Students graduate without: • Proficiency at procedural languages and explicit memory management (in C) • Deep understanding of high level languages’ implementations • Language shift: • Before: Introduction to programming and most assignments in procedural languages. • Upper-division students and graduates were able to easily gain proficiency in C or other procedural langauges. • After: Introduction to programming and most assignments in O-O languages (generally Java) • Upper-division students and graduates find C arcane and difficult to master. • Students knowledge is compartmentalized • The distance between OO and machine language abstractions is too large. • Combining introduction to computer organization and procedural languages will integrate knowledge and increase student competency at programming in procedural languages. What we are trying to do about it…. (a reform to a Junior-level Course in Computer Organization) • Interleaved introduction to C and machine language/assembly. • Addressing modes: C’s abstractions for addressing memory including pointers, arrays, and structs are used to motivate addressing modes • Control flow: Students first reduce control-flow structures to “goto C” and which then directly translates to assembly language. • Arithmetic expressions: Students manually construct parse-tree to identify temporary variables and evaluation order. • Subroutine linkage: C-calling convention used, students write programs with routines in both languages • Interrupts: First level handler in assembly calls C 2nd level handler • Structure of many projects… • First design it in C • Translate components to assembly (when necessary) • Initial results: • Tests: students understand relationship between C abstractions and implementation in assembly language