Editing Conditional (computer programming) (section)

=== History and development ===
In early programming languages, especially some dialects of [[BASIC]] in the 1980s [[home computer]]s, an <code>if–then</code> statement could only contain <code>[[GOTO]]</code> statements (equivalent to a [[Branch (computer science)|branch]] instruction). This led to a hard-to-read style of programming known as [[spaghetti programming]], with programs in this style called ''spaghetti code''.  As a result, [[structured programming]], which allows (virtually) arbitrary statements to be put in statement blocks inside an <code>if</code> statement, gained in popularity, until it became the norm even in most BASIC programming circles. Such mechanisms and principles were based on the older but more advanced [[ALGOL]] family of languages, and ALGOL-like languages such as [[Pascal (programming language)|Pascal]] and [[Modula-2]] influenced modern BASIC variants for many years. While it is possible while using only <code>GOTO</code> statements in <code>if–then</code> statements to write programs that are not spaghetti code and are just as well structured and readable as programs written in a structured programming language, structured programming makes this easier and enforces it.  Structured <code>if–then–else</code> statements like the example above are one of the key elements of structured programming, and they are present in most popular high-level programming languages such as [[C (programming language)|C]], [[Java (programming language)|Java]], [[JavaScript]] and [[Visual Basic]] .

==== The "dangling else" problem ====
{{Main|Dangling else}}
The <code>else</code> keyword is made to target a specific <code>if–then</code> statement preceding it, but for [[Nesting (computing)|nested]] <code>if–then</code> statements, classic programming languages such as [[ALGOL 60]] struggled to define which specific statement to target. Without clear boundaries for which statement is which, an <code>else</code> keyword could target any preceding <code>if–then</code> statement in the nest, as parsed.
 '''if''' a '''then''' '''if''' b '''then''' s '''else''' s2
can be parsed as
 '''if''' a '''then''' ('''if''' b '''then''' s) '''else''' s2
or
 '''if''' a '''then''' ('''if''' b '''then''' s '''else''' s2)
depending on whether the <code>else</code> is associated with the first <code>if</code> or second <code>if</code>. This is known as the [[dangling else]] problem, and is resolved in various ways, depending on the language (commonly via the <code>end if</code> statement or <code>{...}</code> brackets).