Programming style

From Wikipedia, the free encyclopedia

You have new messages (last change).

Programming style refers to a set of rules or guidelines used when writing the source code for a computer program. It is often claimed that following a particular programming style will help programmers quickly read and understand source code conforming to the style as well as helping to avoid introducing faults.

A classic work on the subject was The Elements of Programming Style, written in the 1970s, and largely illustrated with examples from the Fortran language prevalent at the time.

The programming style used in a particular program may be derived from the coding standards or code conventions of a company or other computing organization, as well as the preferences of the author of the code. Programming styles are often designed for a specific programming language (or language family), but some rules are commonly applied to many languages. (Style considered good in C source code may not be appropriate for BASIC source code, and so on.)

Contents

[edit] Elements of good style

Good style, being a subjective matter, is difficult to concretely categorize; however, there are several elements common to a large number of programming styles. The issues usually considered as part of programming style include the layout of the source code, including indentation; the use of white space around operators and keywords; the capitalization or otherwise of keywords and variable names; the style and spelling of user-defined identifiers, such as function, procedure and variable names; the use and style of comments; and the use or avoidance of programming constructs themselves (such as GOTO statements).

[edit] Code appearance

Programming styles commonly deal with the appearance of source code, with the goal of improving the readability of the program. However, with the advent of software that formats source code automatically, the focus on appearance will likely yield to a greater focus on naming, logic, and higher techniques. As a practical point, using a computer to format source code saves time, and it is possible to then enforce company-wide standards without religious debates.

[edit] Indenting

Indent styles assist in identifying control flow and blocks of code. In programming languages that use indentation to delimit logical blocks of code, indentation style directly affects the behavior of the resulting program. In other languages, such as those that use brackets to delimit code blocks, the indentation style does not directly affect the product. Instead, using a logical and consistent indentation style makes code more readable. Compare:

if(hours < 24 && minutes < 60 && seconds < 60){
   return true;
}else{
   return false;
}

or

if(hours < 24 && minutes < 60 && seconds < 60)
{
   return true;
}
else
{
   return false;
}

with something like

if(hours < 24 && minutes < 60 && seconds < 60) {return true;}
else{return false;}

The first two examples are much easier to read because they are indented well, and logical blocks of code are grouped and displayed together more clearly.

This example is somewhat contrived, of course - all the above are more complex (less stylish) than

return hours < 24 && minutes < 60 && seconds < 60;

[edit] Spacing

Free-format languages often completely ignore whitespace. Making good use of spacing in code layout is therefore considered good programming style.

Compare the following examples of C code.

 int count;
 for(count=0;count<10;count++)
 {
   printf("%d",count*count+count);
 }

with

 int count;
 for (count = 0; count < 10; count++)
 {
   printf("%d", count * count + count);
 }

In the C-family languages, it is also recommended to avoid using tab characters in the middle of a line as different text editors render their width differently.

Python uses indentation to indicate control structures, so correct indentation is required. By doing this, the need for bracketing with curly braces ({ and }) is eliminated, and readability is improved while not interfering with common coding styles. However, this frequently leads to problems where code is copied and pasted into a Python program, requiring tedious reformatting. Additionally, Python code can be rendered unusable when posted on a forum or webpage that removes whitespace, on webpages Python code should be enclosed in a "<code> ... </code>" tag to be properly displayed. Haskell similarly has the off-side rule.

[edit] Naming, Logic, and Higher Techniques

[edit] Appropriate variable names

Appropriate choices for variable names are seen as the keystone for good style. Poorly-named variables make code harder to read and understand.

For example, consider the following pseudocode snippet:

get a b c 
if a < 24 and b < 60 and c < 60
  return true
else
  return false

Because of the choice of variable names, the function of the code is difficult to work out. However, if the variable names are made more descriptive:

get hours minutes seconds 
if hours < 24 and minutes < 60 and seconds < 60
  return true
else
  return false

the code's intent is easier to discern, namely, "Given a 24-hour time, true will be returned if it is a valid time and false otherwise."

[edit] Boolean values in decision structures

Some programmers think decision structures such as the above, where the result of the decision is merely computation of a Boolean value, are overly verbose and even prone to error. They prefer to have the decision in the computation itself, like this:

return hours < 12 && minutes < 60 && seconds < 60;

The difference is often purely stylistic and syntactic, as modern compilers produce identical object code for both forms.

[edit] Looping and control structures

The use of logical control structures for looping adds to good programming style as well. It helps someone reading code to understand the program's sequence of execution (in imperative programming languages). For example, in pseudocode:

 count = 0
 while count < 5
   print count * 2
   count = count + 1
 endwhile

The above snippet obeys the two aforementioned style guidelines, but the following use of the "for" construct makes the code much easier to read:

 for count = 0, count < 5, count=count+1
   print count * 2

In many languages, the often used "for each element in a range" pattern can be shortened to:

 for count = 0 to 5
   print count * 2

[edit] See also

[edit] External links

[edit] Coding conventions for languages

[edit] Coding conventions for projects

Retrieved from "http://en.wikipedia.org../../../p/r/o/Programming_style.html"