The for statement can be divided into three separate parts, as shown in Table 5.3.
Table 5.3 for Loop Elements
Syntax Name When Executed Contents
Before any other element of the for statement or the substatement. Often used to initialize loop indices. It can contain expressions or declarations.
Before execution of a given iteration of the loop, including the first iteration. An expression that evaluates to an integral type or a class type that has an unambiguous conversion to an integral type.
At the end of each iteration of the loop; expression1 is tested after expression2 is evaluated. Normally used to increment loop indices.
The for-init-statement is commonly used to declare and initialize loop-index variables. The expression1 is often used to test for loop-termination criteria. The expression2 is commonly used to increment loop indices.
The for statement executes the statement repeatedly until expression1 evaluates to zero. The for-init-statement, expression1, and expression2 fields are all optional.
The following for loop:
for( for-init-statement; expression1; expression2 )
is equivalent to the following while loop:
while( expression1 )