PTHREADS is a set of C examples programs which illustrate the use of the POSIX thread libraries for parallel programming.
MPI is a parallel programming interface for distributed memory systems.
OPEN_MP is a parallel programming interface for shared memory systems.
COND1 demonstrates the use of a condition variable which can cause a process to wait and then resume execution.
DOT_PRODUCT is an extensive example which shows how the dot product of two vectors could be computed.
JOIN1 shows how a thread can wait for other threads to finish.
MUTEX1 shows how a mutex can be used to control the access by different threads to a single data itme.
PTHREAD1 is a simple example which shows how threads are created and terminated.
You can go up one level to the C source codes.