Structured Programming in Software Engineering


Structured programming, or modular programming, is a programming paradigm that facilitates the creation of programs with readable code and reusable components. All current programming languages support structured programming, yet the support methods differ, much like programming language syntax.

Structured Programming in Software Engineering

Building structured code from modules written in various languages may also be feasible when modules or code pieces may be reused from a library, provided that they comply with a common module interface or application program interface definition. Reusing modules, however, can jeopardize data security and governance. Thus, it's critical to establish and implement a privacy policy that restricts module use and grants implicit data access permissions.

An application program should be divided into a hierarchy of independent modules or parts, each of which may contain more of these elements, according to structured programming. Code may be further organized inside each element by utilizing linked logic blocks that are intended to enhance readability and maintainability. These may include while and for, which create loops that keep going until a condition is fulfilled, and case, which compares a variable to a collection of values. A goto statement, or unconditional transfer of control, is obsolete and occasionally unavailable in all structured programming languages.


The structured program theorem provides the theoretical foundation of structured programming. It asserts that any computable function may be expressed using just three program combinations: sequencing, selection, and iteration. However, most publications attribute the finding to a 1966 study by Böhm and Jacopini, maybe because Dijkstra himself referenced this work. How to develop and evaluate an effectively structured program is not covered by the structured program theorem. Dijkstra, Robert W. Floyd, Tony Hoare, Ole-Johan Dahl, and David Gries made significant contributions to the discussion of these topics in the late 1960s and early 1970s.

Almost all computer scientists were persuaded by the end of the 20th century that understanding and utilizing the principles of structured programming is beneficial. Programming structures are now included in high-level programming languages like FORTRAN, COBOL, and BASIC, which did not have them at first.

Key Principles of Structured Programming

  • Top-Down Design: Top-down design is one of the cornerstones of structured programming. Using this method, a big problem is divided into smaller, easier-to-manage subproblems. The approach may then be made more understandable and effective by having developers work on each sub-problem separately.
  • Modularization: Structured programming encourages the development of compact, self-contained modules or functions. Each module covers a certain component of the program, which promotes code reusability and makes maintenance and debugging easier.
  • Structured Flow Control: This paradigm promotes the use of control structures such as conditionals and loops in order to achieve structured flow control. This lowers the possibility of adding mistakes while simultaneously improving the code's clarity.

Elements in Structured Programming

Control Structures

According to the structured program theorem, three types of control structures make up any program:

  • "Sequence" refers to ordered statements or sequentially performed subroutines.
  • "Selection": Depending on the program's condition, one or more assertions are carried out. In most cases, terms like “if, else, endif” are used to explain this. Each condition in the conditional statement should have a maximum of one exit point and at least one true condition.
  • "Iteration": a statement or block that keeps running until a certain state is reached by the program or until all of the elements in a collection have undergone specific procedures. Typically, phrases like while, repeat, for, or dountil are used to indicate this.


Statements can be grouped and handled as a single statement by using blocks. Block-structured languages have a syntax for formally enclosing structures. Examples of this include the curly braces {...} found in C and many later languages.

Types of Structured Programming

Structured Programming in Software Engineering

Three types of structured programming exist:

Procedural Programming

Modules are defined as functions or processes that are invoked in order to carry out a job, together with a set of parameters. After a procedural language starts a process, it receives data.

It is also the most prevalent category, with the following divisions under it:

  • Reusable modules are essentially defined as services with public interfaces by service-oriented programming.
  • The goal of microservice programming is to develop modules that are scalable and robust when deployed in the cloud since they do not internally store data.
  • In technical terms, functional programming refers to the writing of modules from functions, where the outputs of the functions are solely derivable from their inputs. Originally intended for serverless computing, functional programming has come to mean microservices in most contexts.

Object-Oriented Programming (OOP)

It describes a program as a collection of resources or objects that receive orders. A data resource is defined using an object-oriented language and sent to process commands. Programmers using procedural languages could write "Print(object)," but those using object-oriented programming might write "Tell Object to Print."

Third-party Modeling Programming

Database query languages are the most prevalent example of this. Units of code in database programming are linked to database access stages and are updated or executed when such actions take place. The code's structure depends on the database and database access structure. Reverse Polish notation, a math problem format that facilitates the effective solution of complicated equations, is another illustration of a model-based structure. Another example of model-based structured programming is quantum computing, where the language just supplies the necessary model, which the quantum computer needs to organize steps.

Difference between Structured and Unstructured Programming Languages

Structured programming languages make structured programming methods easier or more rigid. Unstructured languages can also support these methods, but doing so requires certain procedures in the program's design and execution. That is to say, organized programming methods predate structured programming languages.

The development of Algorithmic Language (ALGOL) 58 and 60 in the 1950s laid the theoretical foundation for structured programming. Until then, programmers had to explicitly create connected tests and actions using the goto statement or its equivalent to construct condition/action tests, which degraded the code's readability and resulted in what was commonly referred to as spaghetti code. ALGOL included a block structure in which a code element had an action and a condition.

Ten years later, modular programming now widely recognized as synonymous with structured programming emerged when it became evident that developer productivity could be increased through the reuse of common code. In modular programming, a program is split up into semi-independent modules, and each module is invoked as needed. Although some believe that true module independence is necessary for modular programming, most development teams see any program that breaks logic down into discrete parts as modular, even if those parts are part of the same program.

All current programming languages can generate structured code. Likewise, if utilized improperly, they might also result in code that could be accurately characterized as unstructured. Some claim that because unstructured programming languages include goto commands, they don't need to call a different module that returns when finished; however, that definition is very restrictive. It would be more accurate to state that different languages have different strategies for enforcing structure; some need structure, while others allow less organized code.

Advantages of Structured Programming

The benefits of organized programming are numerous. One benefit is that it promotes top-down implementation, which makes code easier to understand and maintain. Because even internal modules may be detached and made independent, placed in libraries, documented in directories, and referenced by several other programs, structured programming also encourages the reuse of code. Finally, everyone agrees that structured programming reduces development time and produces higher-quality code.

These benefits are typically viewed as strong, even decisive, and structured programming is used in almost all contemporary software development.

Disadvantages of Structured Programming

The main drawback of structured programming is that it requires more memory and has worse execution efficiency. The introduction of calls to a module or process, which returns to the caller after it is finished, is the root cause of both of these issues. When needed, system resources and parameters are popped from a stack, which is a queue arranged according to the last in, first out, or LIFO. The overhead related to the module interface increases with the amount of deconstructed program logic or the number of modules involved. Overstructuring and inefficiency are potential hazards for any structured programming language.

If the wrong kind of structure is chosen for the job at hand, structured programming can likewise be used improperly. The most well-known instance is figuring out math problems. Because recursion in code is eliminated and there is no need to explicitly indicate execution order, RPL is an efficient approach to formulate and solve a math problem. Nevertheless, the code generated would be significantly less efficient than the RPL version if the problem were to be presented in procedural or object form within structured programming.


With its focus on organization and clarity, structured programming is still essential in the rapidly changing field of software engineering. When carefully followed, its principles aid in the development of reliable and maintainable software. As we come to the end of our investigation of structured programming, it is evident that its systematic approach is not just a thing of the past but also a guiding principle for work on software projects both now and in the future.

To sum up, developers may address complexity, lower error rates, and promote code reuse by adopting structured programming concepts. A professional with years of experience or a student just starting in the field of software engineering can benefit from knowing and using structured programming to get better results.