semaphores, mutexes, conditional variables,
read-write locks, and
barriers.
❖
A higher-level mechanism is a monitor concept that combines
mutexes and conditional variables and sets some rules for their
interaction to protect shared data.
Using monitors is the most
consistent approach to stream synchronization.
Different types of memory are organized into a hierarchy. At the lower
levels of such a hierarchy, there is a cheaper and slower memory of a larger
volume, and as the hierarchy moves upwards the memory becomes more
expensive and faster (and its volume becomes smaller). The cheapest and
slowest storage device is the hard drive.
It is also called
secondary storage. Faster and more expensive memory is stored in the
memory chips installed on the computer - a memory called the main
memory. Faster storage facilities have
different cache processors, and
at least, these caches are more limited.
Managing memory is a rather difficult task. The required memory
characteristics are often not enough identified, and in order not to interfere
with the work of the user, it is necessary
to implement means of
coordination of different types of memory. Thus, the current application
cannot fit entirely in the main memory,
while unused code can use
tymch and COBOL stored on the hard drive. In this section, we look at
technologies that use primary memory.
