4.1 Roughly speaking, what is a thread?

The state of a thread includes the following:

• Global variables. These are variables that are statically allocated.
• The heap. The heap is a space where objects are allocated dynamically.
• The stack and stack pointer. This is where local variables, parameters and many other states related to subroutines are stored.

Two threads of the same process share global variables and the heap, but each has its own stack and stack pointer. As such, two threads cannot execute on different machines due to the necessity to share memory. However, this also makes it possible for threads to share variables and dynamically allocated objects.