Serial Ports help

[Quantos]

But the same might be said of an analog system.

All digital signals are analog, but not all analog signals are digital.  It takes the combination of layers to make it digital.

[westom]

*DB25 female port is parallel, DB25 male port is serial
A DB25 is not a Centronics 'interface', and D-sub connectors were around some 20 years before Centronics was a company and introduced their connectors.

  Officially IEEE1284 does not specify the connector.  But the Centronics interface that came with Centronics printers became a defacto standard - long before IEEE1284 was created.  Forgot the printer side connector name that also existed long before Centronics created their standard.  But that connector also became a defacto standard for Centronics interfaces.

 Even long before the PC, that female DB25 connector was a minicomputer's interface connector for Centronix printer interfaces - also called parallel port interface in PCs.  A defacto standard that was maintained until recently when computers now no longer come standard with parallel ports.  If it's a 25 pin female D connector on a computer, it is a parallel port - the defacto standard.

  Returning to the OP's question - we use serial ports because data transfers are faster.

[patio]

I'm not gonna pick apart your analogy because i'm tired...but that's quite a few defacto's you used here...

[quaxo]

Officially IEEE1284 does not specify the connector.

Again, this is inaccurate. Not only does it define the connectors, it defines the construction of the cable that links the two ends together.

Using the connectors I mentioned before, IEEE1284 specifies the following cables:
DB25M to DB25M
DB25M to DB25F
DB25M to Centronics
DB25M to mini-Centronics
Centronics to mini-Centronics
mini-Centronics to mini-Centronics

And the following characteristics for those cables:
1. The cable shield must be connected to the connector backing using 360° concentric method.
2. The shield must be a minimum of 85% optical braid coverage over foil.
3. All signals are sent over a twisted pair with their signal ground return.
4. Each pair must have an impedance of 62 ± 6 ohms at 4 to 16 MHz.
5. The maximum crosstalk can be no greater than 10%.

No offense, westom, but you should do a little more research on the topic before offering more advice on it. Oh, and AT&T wasn't founded until the 1980s. RS-232 has been around since the 1960s. AT&T did not create RS-232.

And to answer the OP's actual original question: No, there isn't a speed difference. In computers, the only thing a DB25 COM port has that a DE9 COM port doesn't is a protective ground. Generally unnecessary since both have a common ground. The other 15 pins of a DB25 COM port generally aren't used in serial communications for PCs.