Structured Programming

C is called a structured programming language because to solve a large problem, C programming language divides the problem into smaller structural blocks each of which handles a particular responsibility. Structured programming is a programming approach that focuses on enhancing the clarity, quality, and efficiency of computer programs. It achieves this goal by heavily relying on structured control flow constructs, such as selection (if/then/else) and repetition (while and for) statements, along with block structures and subroutines. Structured or structural programming is often synonymed with few other programming paradigm like Procedural Programming and Modular Programming.

Procedural Programming

Procedural programming focuses on breaking down a program into reusable procedures or functions, which are a fundamental part of structured programming.

Modular Programming

Modular programming emphasizes the decomposition of a program into smaller, self-contained modules, promoting code reusability and maintainability.

Different Structural blocks

Below are the structural blocks –
  • Sequence: Programs are composed of a sequence of instructions that are executed in a sequential order. This means that the instructions are executed one after another, from top to bottom, unless control flow statements alter the execution order.
  • Selection: Structured programming includes conditional statements to control the flow of execution based on certain conditions. Common selection statements include "if-else" and "switch-case." These statements allow the program to make decisions and choose different paths of execution based on specific conditions. Read further on Selection / Decision making blocks if-else-elseif, switch-cases,
  • Iteration: Iteration, or looping, is another crucial element of structured programming. It allows the repetition of a sequence of instructions based on a condition. Common loop structures include "for," "while," and "do-while" loops. Loops enable the execution of a block of code repeatedly until a specified condition is met. Read further on Repetitive loops: For-loop, While-loop, Do-while loop etc
  • Subroutines or Functions: Structured programming promotes the use of subroutines or functions to break down complex programs into smaller, manageable pieces of code. Functions encapsulate a specific set of instructions that perform a particular task. They can be reused multiple times, enhancing code modularity and reusability. subroutines/procedures - functions
  • Single Entry and Exit Points: In structured programming, each subroutine or function typically has a single entry point and a single exit point. This principle aims to ensure clear control flow and avoid complex branching or jumps within the code, enhancing program readability and maintainability.

The program which solves the entire problem is a collection of such structural blocks. Even a bigger structural block like a function can have smaller inner structural blocks like decisions and loops.

Structured programming came into picture after the assembly language, ALGOL 58 and ALGOL 60. Let us go back to the time when structural support was not there in the programming languages. Programming languages used to use goto and jump type of statements to hop between different logical units. A bigger program used to be unorganized and difficult to understand. A need for structured programming came into picture and programming languages started introducing these block structures. Programming languages like C, BASIC, PASCAL, FORTRAN, COBOL gave support to structured programming methodologies.

C structural blocks

Statements and conditions

c condition and statements structural-blocks


c loops structural-blocks

Functions and procedures

c function procedure blocks

Structured blocks examples

Here is an example of Matrix addition program, which is divided into these sub procedures - input matrix, display matrix, add matrix, save result matrix to file. Here is a pictorial structural view of the program.

Matrix addition example

Another good example is calculate student's grade. Program is divided into these sub modules - input student marks, get student record, update student record, display student record, calculate grade. Here is a structural view of the program.

student grade example

Structured programming gave a good organization to programming blocks. But one major drawback is that similar functions cannot be grouped inside a module or class. Also functions cannot be associated to a type or structure. Thus data and functions cannot be bound together. C++ language overcomes these problems by introducing object oriented functionality in its programming capabilities. Object oriented programming is the next enhancement of all structured languages. C++, Java, C# and all modern programming languages support this capability.


  • C structured programming is simple and easy to understand and implement.
  • It is well suited for small size implementation. However this is not restricted. A good design can extend it to large size implementation.
  • Programmers do not require to know complex design concepts to start a new program.
  • Readability: Code is organized into smaller, coherent structures, making it easier to understand and follow by programmers.
  • Maintainability: The modular design allows for easier maintenance, debugging, and updates without affecting the entire program.
  • Reusability: Functions and subroutines enable code reuse, reducing redundancy and saving development time.
  • Efficiency: Utilization of structured control flow constructs, like loops, leads to optimized and faster-performing programs.
  • Error Handling: The use of structured error-handling mechanisms, such as try-catch blocks, results in more robust and stable applications.
  • Top-Down Design: Facilitates the breakdown of complex problems into manageable subproblems, aiding in a systematic approach to software development.
  • Collaboration: Developers can work on separate modules simultaneously, promoting team collaboration and efficient project development.
  • Scalability: The structured approach provides a solid foundation for expanding and scaling software as the project grows.
  • Code Understanding: Easier comprehension of the program's logic and flow, making it more accessible for programmers to modify and extend.
  • Testing: Modular code is conducive to efficient unit testing, enabling developers to isolate and verify specific functionality.
  • Debugging: Smaller, well-defined code blocks simplify the process of identifying and fixing errors and issues.
  • Adaptability: Changes in requirements can be accommodated more easily through well-structured code blocks.
  • Code Optimization: The structured design encourages efficient algorithm implementation and optimization.
  • Code Documentation: Clear organization facilitates better documentation, making it easier to maintain and understand the codebase over time.
  • Reduced Complexity: Structured programming breaks down complex tasks into simpler, manageable components, reducing cognitive load for developers.
  • Learning: It serves as an excellent introduction to programming concepts for beginners due to its systematic and organized approach.
  • Standardization: Promotes the adoption of consistent coding practices and style, enhancing overall code quality.
  • Portability: Well-structured programs are often more portable and can be adapted to different environments and platforms with minimal changes.
  • Maintainable Legacy Code: Converting older, unstructured code into structured form enhances its maintainability and longevity.
  • Enhanced Software Quality: The advantages of structured programming lead to higher-quality software with fewer bugs and issues.


  • Lack of Object-Oriented Features: Structured programming lacks the powerful object-oriented features that provide additional benefits for software development. Data and methods and not be bind together in a module.Polymorphism and inheritance are not available.
  • Scaling : Complex design and full object oriented design cannot be implemented.
  • Limited Expressiveness: The rigid structure might limit the expression of certain complex algorithms or unconventional programming approaches.
  • Code Duplication: Without careful design, code duplication may occur across multiple functions or modules, leading to maintenance issues.
  • Code Length: Structured programming can sometimes result in longer code, which may affect readability and increase the potential for errors.
  • Overuse of Functions: Excessive use of functions can lead to a proliferation of small, specialized functions, making the codebase harder to manage.
  • Readability Overload: Overuse of structured constructs might lead to excessive indentation and nested blocks, reducing code readability.
  • Complexity Management: While structured programming helps manage complexity to some extent, extremely large projects may still become challenging to handle.
  • Learning Curve: Beginners might find it initially challenging to grasp the concept of structured programming due to its rigid organization.
  • Design Overhead: Properly structuring a program requires careful planning and design, adding an overhead at the beginning of the development process.
  • Inflexible Flow Control: The structured control flow constructs may not be ideal for every programming scenario, limiting the flexibility of program flow.
  • Limited Real-time Applications: In some real-time applications, the strict sequential execution may not be suitable for meeting specific timing constraints.
  • Debugging Overhead: Tracing issues across multiple nested structures can be more complex and time-consuming during debugging.
  • Maintenance Complexity: As projects grow and evolve, managing interactions between various structured components can become more challenging.
  • Learning Curve for Legacy Code: When working with legacy unstructured code, transitioning to a structured approach may require significant effort and resources.
  • No Direct Support for Parallelism: Structured programming does not inherently provide features for easy parallelization of code, which is essential in modern multi-core processor.
  • Scalability Concerns: In certain cases, structured programming may not scale well for very large, complex software systems.
  • Inter-module Dependencies: Tightly coupled modules may hinder code maintenance and updates due to cascading changes.
  • Excessive Abstraction: Overuse of functions and subroutines can lead to unnecessary abstraction, making it harder to understand the program's flow.
  • Performance Trade-offs: Some structured constructs may introduce slight performance overhead compared to lower-level programming approaches.
  • Incompatibility with Specific Domains: Certain specialized domains or specific programming tasks might require alternative programming paradigms, rendering structured programming less suitable.
Programmers generally prefer object oriented programming language over structured programming language when implementing a complex gaming applications or front end business applications.

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