Room for Tanuj and John Rennie

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John Rennie

04:56

@Tanuj hi :-)

Tanuj

hey

(: good morning

I have a couple of questions regarding kernels and modular programming etc

would you be free during the next hour ?

kernels and modules and awk and makefile etc

John Rennie

Yes, I'm around for several hours.

Tanuj

@JohnRennie thanks , I've just been reading from the ppts my teacher sent me , and its really confusing

John Rennie

OK ... ?

Tanuj

I am not able to solve any questions related to them

yeah , also I've never worked with Linux as such , so it gets more confusing

@JohnRennie i was reading about modular programming and it kind of sounds like a normal programming environment where we use functions to implement a particular task

is there any difference ?

John Rennie

05:01

Yes, the four things you mention are four completely different and unrelated things.

Tanuj

I'm thinking modular programs are handled by the kernel space whereas normal programs are handled in user space

John Rennie

A module typically means a device driver, so yes they are chunks of code that can be linked into the kernel.

Tanuj

hmm

so like can I say that modules are analogous to functions in a user program ?

John Rennie

Suppose you write a program that does some graphics. You don't want to write all the graphics code so you use a library that contains the graphics code.

Tanuj

@JohnRennie okay

that would be what I would do in a normal user space programming

John Rennie

05:08

So your program might call a function DrawCircle, and the code for this function is in the graphics library not in your program. Your program calls into the graphics library, and when the graphics are done it returns back to your program again.

(all in user space)

Tanuj

@JohnRennie got it

John Rennie

Now suppose you have some device, e.g. a coffee maker, attached to your computer.

Tanuj

yeah

John Rennie

The kernel doesn't know how to operate a coffeemaker because Linus Torvalds didn't think of it when it wrote the kernel.

So the code to operate the coffee maker is put into a module.

Tanuj

okay

right

John Rennie

05:11

Then when something needs to be done with the coffee maker the kernel calls into the module. The module does whatever needs doing then returns to the kernel.

Tanuj

so like we can continue to update the kernel according to our needs by updating it with new modules

John Rennie

So it's like your program using a graphics library except that all this happens in kernel space not user space.

@Tanuj exactly, yes.

Tanuj

Ah , so modules are analogous to functions arent they ?

functions , or subroutines , or libraries

John Rennie

I would have said analogous to libraries i.e. collections of many functions.

Tanuj

@JohnRennie Gotcha