On the Triviality of the Assignment Statement

The assignment statement is a basic programming operation which is used to assign a value to a variable. The assignment statement is needed in all programs which manipulate data. Most programmers assume that this statement is trivial and therefore should not pose conceptual problems for novice programmers. This article investigates the validity of this assumption. We describe a number of misconceptions of the assignment statement in the form of inappropriate mental models for the assignment statement. These were established through a literature review. We used a questionnaire to identify the prior programming experience of the students in a cohort of 1058 students enrolled for an introductory programming course. We classify the respondents into three categories namely those who have never programmed before; those who have previously tried but failed the introductory programming course; and those who claim that they have had prior programming experience. We then asked the students to complete ten questions which ask the outcome of a short program executing assignment statements. The multiple choice questions were designed to identify the mental model of the respondent regarding the assignment statement for a number of cases. We compare the occurrence of correct and wrong metal models in the three groups and discuss our observations as well as their consequences for teaching introductory programming.