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You are learning to make blueberry muffins :
- Find a recipe and acquire the necessary ingredients
(flour, eggs, sugar, butter, blueberries etc)
- Here, recipe is the program
- You are the CPU (the processor of the recipe or information or program)
- The ingredients constitute the inputs, and the muffins the output
- Process is the activity of actually reading the recipe, fetching the
ingredients and baking the cake.
Interruptions from the outside world - the television, the
neighbours etc - start from where you left off.
![figure71](img3.gif)
Figure:
- A process is more than just a program
- I run ls - you run ls - same program, but different
processes (in Unix)
- Less to a process than a program - a single program can invoke more
than one process to complete a task
- Process must be able to create other processes (dynamic process creation)
and destroy those not needed.
- The start-up or initialisation processes present on all OS.
![figure78](img4.gif)
Figure:
- Process creating by Fork and Join in Unix
- To create different child processes, child must execute
exec(filename, arguments)
join = wait(pid)
- Concurrency and synchronisation is mixed
- When a create process call is made to the OS, the OS allocates :
Process id (Pid) = create(filename,arguments)
Allocate storage space
Use other mechanisms to achieve synchronisation with processes already
active
- WinNT supports both duplicating parent's address space and loading a
new program into a process
Omer F Rana
Thu Feb 6 16:13:26 GMT 1997