6. System
Model
A system is an organized group of
related objects or components;
models can be used for
understanding and predicting
the behavior of systems.
8. Deadlock
It is a situation where a set of processes are
blocked because each process is holding a
resource and waiting for another resource
acquired by some other process.
16. Deadlock Prevention, Detection, & Avoidance, and Recovery.
Prevention- This is done by restraining the ways a request can
be made. Since deadlock occurs when all the
above four conditions are met, we try to prevent
any one of them, thus preventing a deadlock.
Detection & Avoidance- We let the system fall into a
deadlock and if it happens, we detect it using a
detection algorithm and try to recover.
When a process requests a resource, the
deadlock avoidance algorithm examines the
resource-allocation state. If allocating that resource
sends the system into an unsafe state, the request is got
granted.
19. Deadlock Prevention, Detection, & Avoidance, and Recovery.
Therefore, it requires additional information such as
how many resources of each type is required by a
process. If the system enters into an unsafe state, it has to take a
step back to avoid deadlock.
Recovery- Some ways of recovery are as follows.
○ Aborting all the deadlocked processes.
○ Abort one process at a time until the system recovers from the
deadlock.
○ Resource Preemption: Resources are taken one by one from a
process and assigned to higher priority processes until the
deadlock is resolved.
22. Swapping
● Swapping is a memory management scheme in which any process can be
temporarily swapped from main memory to secondary memory so that the main
memory can be made available for other processes. It is used to improve main
memory utilization. In secondary memory, the place where the swapped-out
process is stored is called swap space.
23. Swap-out
Swap-out is a method of removing a process from RAM and adding it to the hard
disk.
Swap-in is a method of removing a program from a hard disk and putting it back into
the main memory or RAM.
Types of Swapping
Swap-in
25. Contiguous Memory Allocation
● Contiguous memory allocation refers to a memory management technique in
which whenever there occurs a request by a user process for the memory, one
of the sections of the contiguous memory block would be given to that process,
in accordance with its requirement.
26. Fixed-size Partition
Scheme
This scheme is also known as Dynamic partitioning and iThis technique is also
known as Static partitioning. In this scheme, the system divides the memory into
fixed-size partitions. The partitions may or may not be the same size. The size of
each partition is fixed as indicated by the name of the technique and it cannot be
changed.
This scheme is also known as Dynamic partitioning and is came into existence to
overcome the drawback i.e internal fragmentation that is caused by Static
partitioning. In this partitioning, scheme allocation is done dynamically.
Contiguous memory management techniques
Variable-size Partition Scheme
