From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/SYNTAX/if.html | 133 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 reference/C/SYNTAX/if.html (limited to 'reference/C/SYNTAX/if.html') diff --git a/reference/C/SYNTAX/if.html b/reference/C/SYNTAX/if.html new file mode 100644 index 0000000..8df9bb6 --- /dev/null +++ b/reference/C/SYNTAX/if.html @@ -0,0 +1,133 @@ +if-else keywords. + + + + + + +

+ +

The 'if' and 'else' keywords

+ +

+ +The if-else statement is a two-way decision statement. It is written as + +

+	if ( expression )	statement1;
+	[else			statement2;]
+

+ +The else portion is optional. If the expression evaluates to +true +(anything other than 0) then statement1 is executed. If there is an else +statement and the expression evaluates to +false +statement2 is executed. + +For example + +

+(1)
+	int NumberOfUsers;
+	.
+	.
+	if( NumberOfUsers == 25 )
+        {				/* No else part */
+	  printf( "There are already enough users. Try later.\n" );
+	  return ERROR;
+        }
+	.
+	.
+
+
+(2)	if( a >= b )	larger = a;	/* else part is present */
+	else		larger = b;
+

+ +Consider this code fragment: +

+	if( p == 1 )
+	  if( q == 2 )	r = p * 2 + q;
+        else r = q * 2 + p;
+

+Because the else part is optional, there is an ambiguity when an else is +omitted from a nested if sequence. In 'C', this is resolved by associating +the else with the closest previous if that does not have an else. +Therefore, in the above example, the else part belongs to the if(q==2) +statement. + +The code can be made more readable by explicitly putting parentheses in +the expression, like this + +

+	if( p == 1 )
+        {
+	  if( q == 2 )	r = p * 2 + q;
+        }
+	else r = q * 2 + p;
+
+		OR
+
+	if( p == 1 )
+        {
+	  if( q == 2 )	r = p * 2 + q;
+	  else r = q * 2 + p;
+        }
+

+ +Because the statement in the else part can also be an if statement, a +construct such as shown below is possible in 'C' to create a multiple +choice construct. + +

+	if( expression1 )
+	  statement1;
+	else if( expression2 )
+	  statement2;
+	else if( expression3 )
+	  statement3;
+	.
+	.
+	else
+	  statementN;
+

+ +

Example:

+ Basic if example. +
+

The 'if' and 'else' keywords

Example:

See also: