self doubt

Question

What is protection in term of - "when multiple processes are waiting in the ready queue then one process should not affect the data of another process which is also waiting in the ready queue and this leads to the concept of providing protection between processes in ready queue. " ?

Answer 1

For protection,you nedd to know 2 things -:

1. User Space
2. Kernel Space.

What is User Space?

User Space is the address space where User program resides.

Let a  Process $P_{i}$ is using user space $1000$(address of that location and $P_{j}$ is using $1004$.Now $P_{i}$ is not supposed to access memory data./information of process $P_{j} $and also not of kernel space .

For this purpose protection is provided,so that $P_{i}$ should use only its own address space not of other process neither the kernel.

How this is implemented ?

Using the concept of limit register and base register.

See this 

If $P_{i}$ tries to use other's address space ,then it move to trap /Addresing error.

Answer 2

A process waiting in the ready queue can't access it's own memory let alone affecting others.
Only a running process can drop a bomb.

In a time sharing system, memory protection techniques ensure that a process can access only it's own "Process Image". This includes stack, heap, Read/Only memory, Read/Write Memory and shared library.

If a running process tries to access other process' memory, a segmentation fault occurs and the culprit process is terminated.