FOR - Iteration construct

Key Characteristics

• • Controlled Repetition: The primary function is to execute a set of instructions multiple times, either for a fixed count or based on a dynamic condition.
  • Loop Control Variables: Typically involves one or more variables that are initialized, tested against a condition, and incremented or decremented with each iteration to control the loop's execution.
  • Language-Specific Syntax: The implementation varies significantly across mainframe languages; for example, COBOL uses PERFORM VARYING, REXX uses DO i = start TO end BY step, and PL/I uses DO i = start TO end BY step or DO WHILE.
  • Pre-test or Post-test: Loops can be designed to test the termination condition *before* each iteration (e.g., PERFORM VARYING, DO WHILE) or *after* each iteration (e.g., PERFORM UNTIL with WITH TEST AFTER).
  • Loop Control Statements: Most languages provide mechanisms to alter the normal flow of a loop, such as EXIT (COBOL), `