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else

Last revision 05/14/2024

Description

The 

if...else
allows greater control over the flow of code than the basic 
if
 statement, by allowing multiple tests to be grouped. An 
else
clause (if at all exists) will be executed if the condition in the 
if
statement results in 
false
. The 
else
can proceed another 
if
test, so that multiple, mutually exclusive tests can be run at the same time.

Each test will proceed to the next one until a true test is encountered. When a true test is found, its associated block of code is run, and the program then skips to the line following the entire if/else construction. If no test proves to be true, the default 

else
block is executed, if one is present, and sets the default behavior.

Note that an 

else if
block may be used with or without a terminating 
else
block and vice versa. An unlimited number of such 
else if
branches are allowed.

Syntax

1if (condition1) {
2      // do Thing A
3    }
4    else if (condition2) {
5      // do Thing B
6    }
7    else {
8      // do Thing C
9    }

Example Code

Below is an extract from a code for temperature sensor system

1if (temperature >= 70) {
2      // Danger! Shut down the system.
3    }
4    else if (temperature >= 60) { // 60 <= temperature < 70
5      // Warning! User attention required.
6    }
7    else { // temperature < 60
8      // Safe! Continue usual tasks.
9    }

See also

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