What type of operation does the IF...THEN...ELSE...ENDIF structure in Structured English illustrate?

The IF...THEN...ELSE...ENDIF structure in Structured English illustrates a selection operation. This structure allows a program to evaluate a condition and execute different blocks of code based on whether the condition is true or false.

When the program reaches an IF statement, it checks the specified condition. If the condition evaluates to true, the code within the THEN block is executed. Conversely, if the condition evaluates to false, the code within the ELSE block is executed instead. This clear branching allows for decision-making within the program flow, making it a key component in controlling how a program responds to different inputs or states.

While iteration typically involves repeating a set of instructions until a condition is met, and sequence refers to the linear execution of code statements, selection focuses specifically on diverging code paths based on conditional logic. Therefore, the choice that best describes the function and capability of the IF...THEN...ELSE...ENDIF structure is selection.