AlgoTouch: An Execution-Centered Approach to Incremental Construction of Imperative Programs
Program construction in imperative languages remains largely based on writing textual code that specifies sequences of instructions operating on program data. This approach requires developers to anticipate the effects of instructions on evolving data states, which increases cognitive load and the likelihood of errors during early and incremental development. This paper presents AlgoTouch, an execution-based system for incremental construction of imperative programs through direct manipulation of program data. Rather than assembling syntactic structures, programs are constructed by executing concrete data transformations that are recorded and incorporated into an internal intermediate representation. AlgoTouch relies on an explicit notional machine that exposes data storage, computation, and control flow, enabling continuous alignment between observed execution and program structure. A central contribution of the system lies in its deterministic synthesis of control structures from execution behavior. Conditional statements are derived from observed comparisons, while iterative behaviors are encapsulated in loop macros that support non-linear and incremental construction. This design enables partial and incomplete programs to be executed, refined, and completed while preserving semantic consistency. AlgoTouch automatically generates correct and readable programs in several mainstream imperative languages, including Python, C, C++, and Java. The system is evaluated through engineering-level validation on a representative set of algorithmic benchmarks, demonstrating correctness, expressiveness, robustness, and language independence. By integrating execution, construction, and code generation within a unified architecture, this work introduces an alternative model for interactive program construction and contributes a new class of execution-centered development systems.