What are the main differences between FIDIC 1987 and 1999 red book in terms of Price Adjustment, IPC certification and Claim settlement procedure ?

Interprocess communication (IPC) is a set of programming interfaces that allows a programmer to coordinate activities among different program processes that can run concurrently in an operating system. This allows a program to handle many user requests at the same time. Since even a single user request may result in multiple processes running in the operating system on the user's behalf, the processes need to communicate with each other. The IPC interfaces make this possible. Each IPC method has its own advantages and limitations so it is not unusual for a single program to use all of the IPC methods.