One The syntax format is as follows: If a Boolean expression |C If... else statement| Execute the above program, and the output is as follows:
In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress. if statement can be followed by an optional else statement else statement in a Boolean expression false when it is executed. 5.12.1. Grammar #
if(boolean_expression){
# In the Boolean expression boolean_ Execute when expression is true
}else{
# In the Boolean expression boolean_ Expression executed with false
}
boolean_expression for true , then execute``if`` the code within the block. If the Boolean expression is false , then execute else the code within the block. 5.12.2. Flow chart #
Example #
#/ Usr/bin/perl $a=100# Use the if statement to determine the Boolean expression if ($a<20 "; "a # $a 'a 'a' ($a){# ){# 20 : ; < boolean condition determine else{# execute expression false false, greater if less n n";} n';} of pre print printf statement than the to true true, use value when> A greater than 20
The value of a is: 100
Condition a is false
The value of a is:
Principles, Technologies, and Methods of Geographic Information Systems
102