What can a CALL instruction optionally conclude with?

A CALL instruction is used to transfer control to a subroutine within programming contexts, particularly in languages designed for control systems and embedded systems. When a CALL instruction is executed, the proceeding execution flow can be controlled and optionally concluded with an END instruction. This alignment helps signify the completion of subroutine execution, allowing for a structured return to the point of origin from where the CALL was executed.

The END instruction effectively denotes that no further operations for that subroutine are pending, establishing a clear boundary for the execution scope. This clarity is essential for maintaining organized and readable code, allowing other programmers (or future you) to easily understand where a subroutine begins and ends, thus facilitating better management of program control flow.

Other potential options, while relevant in specific contexts, do not serve as appropriate conclusions to a CALL instruction as fundamentally as the END instruction does. A WAIT condition typically involves pausing execution until a specific event occurs, a JUMP instruction alters the execution flow to another part of the program directly, and a PULSE command generates an output signal for a predefined duration without serving as a structural end to a subroutine. Therefore, the END instruction is integral for conclusive control flow management following a CALL instruction.