In computing

Computing

Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

, hand coding means editing the underlying representation of a document

Document

The term document has multiple meanings in ordinary language and in scholarship. WordNet 3.1. lists four meanings :* document, written document, papers...

 or a computer program

Computer program

A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

, when tools that allow working on more sophisticated representation also exist. Typically this means editing the source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

, or the textual representation of a document or a program, instead of using a WYSIWYG

WYSIWYG

WYSIWYG is an acronym for What You See Is What You Get. The term is used in computing to describe a system in which content displayed onscreen during editing appears in a form closely corresponding to its appearance when printed or displayed as a finished product...

 editor that always displays an approximation of the final product. It may also mean translating the whole or parts of the source code into machine language manually instead of using a compiler

Compiler

A compiler is a computer program that transforms source code written in a programming language into another computer language...

 or an automatic translator.

The reasons to use hand coding include the ability to:

• Use features or refinements not supported by the graphical editor or compiler
• Control the semantics
  Semantics
  Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....
  
   of a document beyond that allowed by the graphical editor
• Produce more elegant source code to help maintenance and integration
• Produce better performing machine code than that produced by the compiler (see optimization
  Optimization (computer science)
  In computer science, program optimization or software optimization is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources...
  
  )
• Avoid having to pay for expensive WYSIWYG Editors. Note that there are some open-source editors available on the web, however.
• Develop an understanding of the methods underlying a common level of abstraction. For example, although it has become rare in real-life scenarios, computer science students may be required to write a program in an assembly language
  Assembly language
  An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
  
   to get a notion of processor register
  Processor register
  In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...
  
  s and other basal elements of computer architecture
  Computer architecture
  In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....
  
  .

However, hand coding may require more expertise and time than using automatic tools.