Software Engineering Fundamentals

About Rajib Mall

• Dr. Rajib Mall is a Professor in the Department of Computer Science and Engineering at IIT Kharagpur.
• He holds a B.E., M.E., and Ph.D. from the Indian Institute of Science, Bangalore.
• He was previously employed at Motorola (India) and joined IIT Kharagpur in 1994.

What is Software Engineering?

• Software engineering is a systematic approach to developing, operating, and maintaining software.
• It leverages a collection of techniques, methodologies, and guidelines based on past experience.
• It applies engineering principles to software development.

IEEE Definition of Software Engineering

• Software engineering is defined as the application of a systematic, disciplined, and quantifiable approach to the development, operation, and maintenance of software.

Software Crisis

• Software products often fail to meet user requirements.
• They are expensive, difficult to modify, debug, and enhance, and are often delivered late.
• Software development frequently uses resources non-optimally.
• Software development costs significantly outweigh hardware costs, highlighting the crucial role of efficiently developing software.

Standish Group Report

• The report shows that 28% of software projects are successful, 49% are delayed or overrun, and 23% are canceled.

Exploratory Programming Style

• The exploratory style of programming, often used in early software development, becomes increasingly difficult to manage in team development environments.
• The effort required to develop software grows exponentially with its size, leading to inefficiencies and breakdowns when software becomes large.

Human Cognition Mechanism

• Human memory consists of two parts: short-term memory and long-term memory.
• Incoming information is first processed in the short-term memory, where it can be lost due to decay or displacement by new information.
• Information from long-term memory can be retrieved into the short-term memory for processing.
• Relating multiple items together, called chunking, helps consolidate information and reduce memory burden.

Decomposition

• The decomposition principle suggests breaking down a problem into smaller, more manageable parts to simplify its resolution.
• However, it's important to ensure that the decomposed parts are relatively independent of each other for this approach to be effective.

Importance of Software Engineering in Developing Large Programs

• Software engineering equips individuals with the skills to develop large programs.
• It provides systematic techniques for handling the exponential growth in complexity as program size increases.
• It emphasizes abstraction (modelling) and decomposition to manage complexity.

Benefits of Studying Software Engineering

• Studying software engineering helps develop skills for efficient development of large programs.
• It teaches systematic techniques for specification, design, user interface development, testing, project management, maintenance, and more.
• It fosters an understanding of challenges that arise in team development environments.
• It equips individuals with the skills to become more productive and high-quality programmers.

Types of Software Projects

• Software projects can be categorized as products (generic software) or services (custom software).
• The global software market is valued in trillions of US dollars, with approximately equal proportions in products and services.
• The service sector is experiencing rapid growth.
• Significant reuse of existing software components is common practice.

Computer Systems Engineering

• Computer systems engineering involves the development of both software and specific hardware for a product.
• This area encompasses software engineering and involves deciding whether tasks are best executed through software or hardware.
• Hardware simulators are frequently used to test and develop software during the design process.
• Hardware and software are often developed concurrently.
• Integration and testing of hardware and software are essential phases.

Emergence of Software Engineering Techniques

• Early computer programming in the 1950s relied heavily on assembly language, with program sizes limited to a few hundred lines of code.
• Programmers developed their own coding styles, often driven by intuition, resulting in the exploratory or build-and-fix programming style.

High-Level Language Programming (Early 60s)

• The introduction of high-level languages like FORTRAN, ALGOL, and COBOL significantly reduced software development efforts.
• Although high-level languages simplified development, the exploratory programming style remained prevalent.
• Program sizes were limited to a few thousand lines of source code.

Control-flow Based Design (Late 60s)

• Dijkstra's influential article, "Goto Statement Considered Harmful," advocated for structured programming and contributed to the shift away from using GO TO statements in programming.
• It was concluded that three fundamental programming constructs (sequence, selection, and iteration) are sufficient to express any programming logic, leading to the development of structured programming methodology.

Structured Programming

• Structured programs adhere to three key constructs: sequence, selection, and iteration.
• Structured programs are developed using modular programming techniques.
• While structured programming emphasizes these constructs, some deviations are occasionally permitted for practical reasons like premature loop exits or exception handling.

Benefits of Structured Programming

• Structured programs are easier to read, understand, maintain, and develop.
• They also tend to be less buggy than programs developed using unstructured approaches.
• Research has shown that programmers make fewer errors when using structured programming constructs like if-then-else and do-while compared to GO TO statements.

Data Structure-Oriented Design (Early 70s)

• As program sizes increased, the importance of designing effective data structures became increasingly apparent, taking precedence over control structure design.
• Data structure-oriented design techniques emphasize deriving a program structure from its data structure, which can enhance efficiency and maintainability.