Noob Question about Librarys

[captian jaster]

I always wondered what's the difference between making a separate unit and building a DLL?
Except for the extra file, why do developers do this?

[Leledumbo]

I always wondered what's the difference between making a separate unit and building a DLL?

Units are Pascal specific way to create modular programs, while DLL is language independent, but they have quite a lot of restrictions that you have to be aware of. The advantage of DLL is that the application is modular at executable level, meaning that when you need to update just some parts of your applications (to your customer for instance) they just need to download several small files, while in the case of units (which is integrated in the executable), they have to re-download the whole file.

Except for the extra file, why do developers do this?

As stated, it's to create modular programs. Modular programs allow people to work in team concurrently (except when a module depends on another), it also makes compilation faster since the compiler will only compile changed or newly added modules, it saves a lot of typing since you don't code the same thing again and again.

[captian jaster]

I always wondered what's the difference between making a separate unit and building a DLL?

Units are Pascal specific way to create modular programs, while DLL is language independent, but they have quite a lot of restrictions that you have to be aware of. The advantage of DLL is that the application is modular at executable level, meaning that when you need to update just some parts of your applications (to your customer for instance) they just need to download several small files, while in the case of units (which is integrated in the executable), they have to re-download the whole file.

Except for the extra file, why do developers do this?

As stated, it's to create modular programs. Modular programs allow people to work in team concurrently (except when a module depends on another), it also makes compilation faster since the compiler will only compile changed or newly added modules, it saves a lot of typing since you don't code the same thing again and again.

Never looked at it that way..
Another question: Would anything I add into a library be usable for other developers like C?

[TurboRascal]

Units are Pascal specific way to create modular programs

Hmm... I believe that's actually the modula-specific way which Borland adopted for use with Pascal...

Another question: Would anything I add into a library be usable for other developers like C?

Yes, it could be. You should export routines so they could use it, say as cdecl...

[Leledumbo]

Hmm... I believe that's actually the modula-specific way which Borland adopted for use with Pascal...

Really? Well... that explains why the format is the same, only differs in keywords (MODULE -> unit, DEFINITION -> interface, etc.)

Would anything I add into a library be usable for other developers like C?

Yes, if you intend to do that. Just be aware about how C compiler looks for symbols (read the docs about name mangling and interfacing to C) and what (or how) parameters could be passed between them.

[captian jaster]

Hmm... I believe that's actually the modula-specific way which Borland adopted for use with Pascal...

Really? Well... that explains why the format is the same, only differs in keywords (MODULE -> unit, DEFINITION -> interface, etc.)

Would anything I add into a library be usable for other developers like C?

Yes, if you intend to do that. Just be aware about how C compiler looks for symbols (read the docs about name mangling and interfacing to C) and what (or how) parameters could be passed between them.

Thanks guys..
Also Oberon 2 and Modula 2(And Zonnon) all use the Module keyword..
Modula came out after Pascal I believe..

[TurboRascal]

Yes, and Borland played with Modula2 for a while, but they decided to abandon work on the compiler. Afterwards they "borrowed" modules concept from it to improve their Pascal products...

[captian jaster]

Yes, and Borland played with Modula2 for a while, but they decided to abandon work on the compiler. Afterwards they "borrowed" modules concept from it to improve their Pascal products...

Didn't pascal always have Units?
The only real one up Modula had on pascal was modularity..
And though Nick did jump ship on the Modula project it was continued in Modula 2 and Oberon(2).(Nonetheless)

[Leledumbo]

Didn't pascal always have Units?

Nope, check ISO 7185. Original Pascal was damn far from Modern Pascal.

[captian jaster]

Didn't pascal always have Units?

Nope, check ISO 7185. Original Pascal was damn far from Modern Pascal.

Damn far?
Wow...

[mas steindorff]

Damn far?
Wow...

The ideal of units did not come about until d4.  before that we used "include" to break up the code into different files (what a pain). before that that, you just used a cavus or burlap bag to carry your project around

[Leledumbo]

Damn far?
Wow...

Yeah, it's the truly Pascal as educational language:

• No units
• No pointer aritmetic
• No object orientation
• No typecasts (well, this one is actually good, but we don't have conversion functions between all base types)
• No untyped pointer
• Overstrict type checking
• Statically sized strings (which assignment incompatible with other strings of different size!)
• Statically sized arrays
• etc.

The ideal of units did not come about until d4

d4 = Delphi 4? AFAIK TP (or even UCSD) already had it long before that

[mas steindorff]

d4 = Delphi 4? AFAIK TP (or even UCSD) already had it long before that

I think your right, it was TP4 or 5.  what was the frist delphi rev called?

[Leledumbo]

it was TP4

http://borlandpascal.wikia.com/wiki/Borland_Pascal

[captian jaster]

Thank you for all the answer's
But when should I use stdcall?