executable code versus non-executable code

[Guest Spin]

Gurus,

 

Today, I overheard four guys in a meeting bandying about executable code

versus non-executable code. I couldn't quite follow but what I thought I

heard was executable code was things like exe's and non-executable code was

like dll's (they can't be executed directly, they must be called by

something else. Is my understanding close to correct?

 

--

Spin

[Guest Alun Jones]

"Spin" <Spin@invalid.com> wrote in message

news:6iokckFrmbjvU1@mid.individual.net...<span style="color:blue">

> Today, I overheard four guys in a meeting bandying about executable code

> versus non-executable code. I couldn't quite follow but what I thought I

> heard was executable code was things like exe's and non-executable code

> was like dll's (they can't be executed directly, they must be called by

> something else. Is my understanding close to correct?</span>

 

It's a bit of an artificial distinction, because the code in a DLL is the

same kind as the code in an EXE, and EXEs are run by causing them to load -

in other words, they don't just run by themselves.

 

Code doesn't just run by itself, it has to be loaded by other code, in a

chain of execution that goes all the way back to the boot-loader, which is

loaded by the hardware.

 

Alun.

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[Guest FromTheRafters]

"Spin" <Spin@invalid.com> wrote in message

news:6iokckFrmbjvU1@mid.individual.net...<span style="color:blue">

> Gurus,

>

> Today, I overheard four guys in a meeting bandying about executable code

> versus non-executable code. I couldn't quite follow but what I thought I

> heard was executable code was things like exe's and non-executable code

> was like dll's (they can't be executed directly, they must be called by

> something else. Is my understanding close to correct?</span>

 

I suppose you would have to ask them what they meant.

 

To me, non-executable code would be code that still

required additional translation before it could execute.

Source code for instance would be non-executable

in most cases.

 

When the code reaches a form that the user can cause

the translation and execution of without any further

action needed, I would consider it executable. This

means that scripts are executable code because once

invoked - no further action is required by the user.

PE files contain executable code because once invoked

the translation into an executable image and loading

and execution of that image takes place without further

action by the user. DLLs and PEs differ in the way they

are invoked and can differ in as little as one bit in the

header IIRC.

[Guest Spin]

That brings up another question I've always had. In Task Manager, if you

click the Processes tab, the first column is titiled "Image Name". Why are

running .exe''s sometimes referred to as "images" anyway? I ask b/c you

made the same reference.

[Guest FromTheRafters]

I can only guess at this one, it probably results from the

fact that the state of memory contents used to be able

to be displayed as a bitmap. Bitmaps would allow you

a more visual representation of memory's contents. An

image of the memory.

 

Essentially, when a loader translates an executable file's

contents into a ready to run form and places it in memory

it can be thought of as an executable image.

 

"Spin" <Spin@invalid.com> wrote in message

news:6ito18Fh44lU1@mid.individual.net...<span style="color:blue">

> That brings up another question I've always had. In Task Manager, if you

> click the Processes tab, the first column is titiled "Image Name". Why

> are running .exe''s sometimes referred to as "images" anyway? I ask b/c

> you made the same reference.

> </span>