Based on the provided reference, a structured program is fundamentally characterized by how its building blocks are designed to specify functions.
The Defining Characteristic: Pattern Specifies Function
According to the reference, a key trait of a structured program is having each instance of each specific pattern specify a function. This means that the recognizable units or segments within the program's code are constructed in such a way that they clearly define a particular input-to-output relationship.
Understanding the Function Specification
The reference provides a precise definition of what is meant by a "function" in this context:
A function is what the correspondence is between input data as sets of independent variables of some specified domains and output data as sets of dependent variables of some specified ranges.
Let's break down this definition:
- Correspondence: The core of the function is the established relationship or mapping.
- Input Data: This is the data the pattern receives. It's viewed as sets of independent variables.
- Specified Domains: For each input variable, there is a defined set of possible values it can take (its domain).
- Output Data: This is the data the pattern produces. It's viewed as sets of dependent variables.
- Specified Ranges: For each output variable, there is a defined set of possible values it can fall within (its range).
In essence, a structured program, according to this characteristic, is composed of patterns where every occurrence of a pattern clearly defines how specific inputs (from their defined domains) are related to, or transformed into, specific outputs (within their defined ranges).
Practical Insight
This characteristic emphasizes modularity and predictability. By ensuring each program pattern clearly specifies a function, developers can understand the purpose and behavior of different code sections by looking at their inputs and expected outputs.
- For example, a common pattern might be calculating a value based on user input. If this pattern specifies a function, you know exactly what output to expect for any given input within the defined range, making the code easier to reason about, test, and maintain.
This definition highlights the importance of clearly defined roles and data transformations for different parts of the program code.
