Low-level design (LLD) is a component-level design process that follows a step-by-step refinement process. This process can be used for designing

data structures In computer science, a data structure is a data organization and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, and the functi ...

, required

software architecture Software architecture is the set of structures needed to reason about a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements a ...

source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

and ultimately,

performance A performance is an act or process of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Performance has evolved glo ...

algorithms In mathematics and computer science, an algorithm () is a finite sequence of mathematically rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for per ...

. Overall, the

data Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted for ...

organization may be defined during requirement analysis and then refined during data design work. Post-build, each component is specified in detail. The LLD phase is the stage where the actual software components are designed. During the detailed phase the logical and functional design is done and the design of application structure is developed during the high-level design phase.

Design phase

A design is the order of a system that connects individual components. Often, it can interact with other systems. Design is important to achieve high reliability, low cost, and good maintain-ability. We can distinguish two types of program design phases: * Architectural or

high-level design High-level design (HLD) explains the architecture that would be used to develop a system. The architecture diagram provides an overview of an entire system, identifying the main components that would be developed for the product and their interf ...

* Detailed or low-level design Structured flow charts and HIPO diagrams typify the class of software design tools and these provide a high-level overview of a program. The advantages of such a design tool are that it yields a design specification understandable to non-programmers and provides a good pictorial display of the module dependencies. A disadvantage is that it may be difficult for software developers to go from a graphic-oriented representation of software design to implementation. Therefore, it is necessary to provide little insight into the algorithmic structure describing procedural steps to facilitate the early stages of software development, generally using Program Design Languages (PDLs).Survey of Program Design Languages (PDLs): Brian A. Nejmeh, Herbert E. Dunsmore

Purpose

The goal of LLD or a low-level design document (LLDD) is to give the internal logical design of the actual program code. Low-level design is created based on the high-level design. LLD describes the class diagrams with the methods and relations between classes and program specs. It describes the modules so that the programmer can directly code the program from the document. A good low-level design document makes the program easy to develop when proper analysis is utilized to create a low-level design document. The code can then be developed directly from the low-level design document with minimal debugging and testing. Other advantages include lower cost and easier maintenance.

References

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