Program structure and design

Abstract

This article models program design as a process of search through the program structure. Some of this structure is captured in the final program code, but much of the fine structure is impIicit in the design process and is not apparent in the final artifact. Viewed from a procedural perspective, a program consists of a set of roles connected by linear order; this is the way a serial computer views a program. Viewed from a functional perspective, a program consists of a set of actions connected by data and control flow dependencies, so they define a nonlinear plan that can be used by a parallel machine. A person sees a program as a set of nodes connected through their data flow, control flow, or Iinear order. Nodes occur at many Ieveis of description, from the most basic concrete node that corresponds to a line of code, up to an abstract node that may consist of one or more routines of arbitrary size.My thanks to Clayton Lewis for pieces of the puzzle, and to the reviewers for their excellent comments. The model owes a great debt to the work of

Display navigation by an expert programmer

“…We refer to this guided search as probing. At a high level, probing is similar to Rist's cuebased memory search [17]. It also corresponds closely to the mechanistic aspects of the Model Human Processor's long-term memory [3].…”

“…It could be that she somehow keeps all such knowledge in working memory for a long time while juggling other tasks, but this is not cognitively plausible. An alternative is to posit a limited working memory, dictating that the programmer must externalize situation knowledge onto paper or the display [4,5,17]. However, there is no evidence that our programmer externalizes knowledge.…”

“…For the model, the string ^operator, underlined on the upper left of Figure 4, is the beacon [2,17,19] (sp chunk-128 :chunk (goal <gl> "operator <ol> "state <sl>) (<ol> "name s-constructorl6 "type s-constructor) (<sl> "assigners <al>) (<al> "n <n2>) (<n2> "max <nl>) (<nl> "head <ul>) (<ul> -"referent <r*l>) -> (<ul> "referent <rl> + "referent (<rl> "referent-of <ul> + "type i comprehend chunk tests, and note in WM that it has seen an operator test in a chunk before.…”

Intention-based scoring

“…Studies that focus on the content and structure of this knowledge generally identify structured "chunks" that achieve a variety of goals, sometimes called schemata [9] or plans [10]. In terms of such theories, two key problems have been suggested as a way of understanding what programmers must do to produce a program [3]:…”

Computer-science education as a cultural encounter

“…Most of these studies concern knowledge of expert and novice programmers, with emphasis on novice difficulties [23]. In addition, there has been emphasis on determining the knowledge needed to bring about effective strategies and in identifyingthe resulting abilities that emerge [19]. Recently, however, interest has been growing regarding the potential of the socio-cultural perspective on learning to advance research in CS education [1,9,13,14,15].…”