How can I correctly setup attachInterrupt() in this sketch?

GolamMostafa September 20, 2021, 1:43pm 25

What is this critical section? Not much is found in the referenced document of Gammon.

Topic		Replies	Views
Interrupts Syntax & Programs	43	65289	May 6, 2021
Bot Interrupt Pins quit working. 3rd Party Boards	22	5857	May 6, 2021
Info su Interrupt0, Timer/Counter1, Input Capture e Output Compare Generale	65	21947	May 7, 2021
2 Interrupts, 2 Pins, Simultaneous usage Programming	52	26257	May 5, 2021
chiarimenti sugli interrupt Generale	78	22700	May 7, 2021