- Process:
- Process =
a program that
is running
- A number of
programs can be
running inside
a computer
Example: 3 processes running inside a computer
- Process =
a program that
is running
- Current process:
- Current process =
the process (= running program)
that is using the
CPU to
execute its
instructions
- Example:
- Suppose we have 3 running programs
(= process) stored
inside the computer memory:
- The program counter PC
contains a value that
is within running program P2:
- Then:
- The CPU will
fetch instructions
from running program (process) P2
- In other words:
- Process P2 is using the CPU to execute its instructions
Therefore: process P2 is the current process
- The CPU will
fetch instructions
from running program (process) P2
- Suppose we have 3 running programs
(= process) stored
inside the computer memory:
- Current process =
the process (= running program)
that is using the
CPU to
execute its
instructions
- Facts:
- There can be many
processes (= running programs)
inside a computer
But: there is only one current process (in a single CPU computer)
- I.e.: one process is being executed at any one time
- The current process can
store
intermediate result of its
computations in the
registers of the
CPU
That means:
- When another running program
wants to use the
CPU:
- We must
save the
values of the
registers
of the current process
(Otherwise, the intermediate resilts will be lost and can not be recovered !!!)
- We must
save the
values of the
registers
of the current process
- When another running program
wants to use the
CPU:
- There can be many
processes (= running programs)
inside a computer