The world, IвЂ™m sorry to say, is not perfect and the world of computers even less so. Of course, a perfect world would have also have fairies and other benevolent spirits to help usher the data along and protect it from all the evil imps and energies lurking about trying to debase and disgrace the singular purity of serial transfer. This is all that would be necessary to move this signal from one place to another without further ado. In a perfect world, a single circuit - nothing more than two wires, a signal and a ground. The later in the string, the more important the bit. The position of a bit in a pulse string gives it its value. That is, the designation of bus line they travel down confers value. The bits of parallel data are coded by their position. The change marks a significant difference in coding. This form of communication earns its name вЂњserialвЂќ because the individual bits of information are transferred into a long series. From a broadside flat advancing line of digital soldiers, into a single file pulse chain like all the soldiers running along one behind another, in single file. Ok, each RS232 serial port, you see, takes the 32 bits (8 and 16 bits in days gone by) your computer exchanges across its data bus then turns them sideways. Oh my god! What a sweeping statement I'd better get on and explain why, otherwise I'll be swamped with emails from people telling me 'NO THEIR NOT'. No matter whatever the name and standard, all serial ports are the same, at least from a functional point of view. RS232 9 Pin D type and 25 pin D type connectors.ДЄ bit of serial communications background. Hence it was shrunk to the 9 pin connector over time. Larger connectors were needed because the datasets and terminals probably carried more signals and power than they do now. Of course I jest, the 25 pin RS232 connector is mearly legacy from the early days of RS232 serial communications. I guess they felt like giving the data lines a bit more room to stretch out, perhaps it's the RS232 pinouts equivalent of flying first class! You can see the RS232 serial port pinout numbers are different for the 9-pin and the 25-pin type connections. The table below, although it does looks a bit boring I'll agree, actually says what the RS232 serial port pinouts designation is. Here you can learn all about the RS232 pinouts designation and what it means to our dear old little friend, the humble RS232 port.

9 pin serial connection