Why threads are referred to as light-weight processes? What resources are used when a thread is created? How do they differ from those used when a process is created?

Does shared memory provide faster or slower interactions between user processes? Under what conditions is shared memory not suitable at all for inter-process communications?

Question # 2 Why threads are referred to as light-weight processes? What resources are used when a thread is created? How do they differ from those used when a process is created? Question # 3 Does shared memory provide faster or slower interactions between user processes? Under what conditions is shared memory not suitable at all for inter-process communications