Difference between Process and Thread
S.N.
Process
Thread
1
Process is heavy weight or resource
intensive.
Thread is light weight taking lesser resources
than a process.
1
Process switching needs interaction with
operating system.
Thread switching does not need to interact with
operating system.
1
In multiple processing environments each
process executes the same code but has its
own memory and file resources.
All threads can share same set of open files,
child processes.
1
If one process is blocked then no other
process can execute until the first process
is unblocked.
While one thread is blocked and waiting, second
thread in the same task can run.
1
Multiple processes without using threads
use more resources.
Multiple threaded processes use fewer
resources.
1
In multiple processes each process operates
independently of the others.
One thread can read, write or change another
thread's data.
Advantages of Thread
Thread minimize context switching time.
Use of threads provides concurrency within a process.
Efficient communication.
Economy- It is more economical to create and context switch threads.
Utilization of multiprocessor architectures to a greater scale and efficiency.
Types of Thread
Threads are implemented in following two ways
User Level Threads
-- User managed threads
Kernel Level Threads
-- Operating System managed threads acting on kernel, an
operating system core.
OS - Memory Management
Memory management is the functionality of an operating system which handles or manages
primary memory. Memory management keeps track of each and every memory location either it
is allocated to some process or it is free. It checks how much memory is to be allocated to
processes. It decides which process will get memory at what time. It tracks whenever some
memory gets freed or unallocated and correspondingly it updates the status.
Memory management provides protection by using two registers, a base register and a limit
register. The base register holds the smallest legal physical memory address and the limit register
specifies the size of the range. For example, if the base register holds 300000 and the limit
register is 1209000, then the program can legally access all addresses from 300000 through
419999.
Instructions and data to memory addresses can be done in following ways
Compile time
-- When it is known at compile time where the process will reside,
compile time binding is used to generate the absolute code.
Load time
-- When it is not known at compile time where the process will reside in
memory, then the compiler generates re-locatable code.
Execution time
-- If the process can be moved during its execution from one memory
segment to another, then binding must be delayed to be done at run time
Dynamic Loading
In dynamic loading, a routine of a program is not loaded until it is called by the program. All
routines are kept on disk in a re-locatable load format. The main program is loaded into memory
and is executed. Other routines methods or modules are loaded on request. Dynamic loading
