Hardware, Memory & Number Systems

high importance7 formulas⚡ 14 shortcuts6 subtopics

Overview Learn (6)Formulas (7)Examples (5)Practice (97)

Ports and connectors

⏱ 4 min read🧩 5 question types🎯 15 practice Q

The idea in one minute

A port is a socket on the computer where a cable or device plugs in. Each port has one job, such as video, network or keyboard. Exams ask which port fits which job. Learn the job of each port and the serial and parallel difference.

What a port is

A port is a socket on the cabinet. A cable or device plugs into it. Every port has a job: carry video, join a network, take a keyboard.

Ask one question in the exam: what does the stem want the port to carry?

Video: VGA, HDMI, DisplayPort.
Network: Ethernet.
Old keyboard and mouse: PS/2.
Everything else today: USB.
Sound: the 3.5 mm audio jack.

Serial and parallel ports

	Serial port	Parallel port
Bits per transfer	One bit at a time	A whole byte (8 bits) at once
Wires	Few	Many
Distance	Long, less interference	Short
Classic use	Old modems and mice (COM port)	Old printers (LPT port)

Tip: Serial is a single lane. Parallel is a multi-lane highway.

The port table

Port	Job
USB (Universal Serial Bus)	Pen drives, keyboards, phones. Hot-swappable. Supplies 5 V power.
HDMI	Digital video and audio in one cable
VGA	Analog video only. 15 pins, blue. No sound.
DisplayPort	Digital video and audio
Ethernet (RJ-45)	Wired network or LAN
PS/2	Round 6-pin socket for old keyboard and mouse
Audio jack (3.5 mm)	Speakers, headphones, microphone
Serial (COM or RS-232)	One-bit-at-a-time old data link
Parallel (LPT)	Old 25-pin printer port

On the audio jack, green is for output and pink is for the microphone.

USB facts

Hot-swappable means you connect or remove it while the computer runs. No restart is needed.
USB supplies power. So pen drives and small keyboards need no adapter.
Speeds grow with each version. USB 2.0 is about 480 Mbps. USB 3.0 is about 5 Gbps.
USB Type-C is the small, reversible oval plug on phones and laptops.

Stem words and their answers

Stem words	Answer
Picture and sound, one digital cable	HDMI
Old blue connector, video only	VGA
One bit at a time	Serial (COM)
Printer port of old machines	Parallel (LPT)
Network cable socket	Ethernet or RJ-45
Round old keyboard and mouse sockets	PS/2
Plug in without restarting	USB
Speakers, green round hole	3.5 mm audio jack

A 10-second method

Underline the job in the stem: video, sound, network or data direction.
Match that job to a row in the port table.
If two options look close, drop the one that lacks a feature the stem asks for.

Watch: VGA fails any stem that mentions audio. Parallel fails any stem that mentions long distance.

Question types you will see

Each type: how to recognise it, the method step by step, and one question to try.

Type 1very common4 practice Q

Serial vs parallel comparison

How to spot it:

'One bit at a time', 'byte at once', 'COM port' or 'LPT port'.

Method

Serial: 1 bit at a time, few wires, long distance.
Parallel: 8 bits (a byte) at once, short distance.
Parallel was the old printer port (LPT).
In statements, check each number for a reversal.

Why it works:

The two ports differ in how many bits move together.

Try this

A parallel port transfers how much data per transfer?

Show solution

A parallel port has 8 wires side by side.
So a whole byte moves at once.

Answer

A full byte (8 bits)

Type 2very common4 practice Q

Port identification by purpose

How to spot it:

'Which port connects...' or 'used to connect a...'.

Method

Underline the job in the stem.
Network: Ethernet or RJ-45.
Digital audio and video: HDMI or DisplayPort.
Old keyboard and mouse: PS/2. Speakers: 3.5 mm jack.

Why it works:

Ports are defined by what they carry.

Try this

Which port connects a computer to a wired LAN?

Show solution

A LAN needs a network cable.
That cable plugs into the RJ-45 socket.

Answer

Ethernet port (RJ-45)

Type 3very common3 practice Q

USB facts

How to spot it:

'Hot-swappable', 'supplies power' or 'USB 3.0 speed'.

Method

Hot-swappable: plug and unplug while the PC runs.
USB carries 5 V power with the data.
USB 2.0 is about 480 Mbps. USB 3.0 is about 5 Gbps.
Type-C is the small reversible plug.

Why it works:

USB is the universal port on modern machines.

Try this

USB is called hot-swappable because...

Show solution

You can connect or remove a device while the computer runs.
No shutdown or restart is needed.

Answer

It can be plugged in or removed while the computer is running

Type 4common2 practice Q

Display and audio ports

How to spot it:

'Analog video only', 'audio and video', 'green socket' or 'pink socket'.

Method

VGA is analog, video only, 15 pins.
HDMI and DisplayPort are digital and carry video and audio.
On the audio jack, green is output for speakers.
Pink is the microphone.

Why it works:

Only HDMI and DisplayPort carry sound with video.

Try this

Which port carries analog video only, with no audio?

Show solution

It is the 15-pin blue connector.
HDMI and DisplayPort are digital, so they are out.

Answer

VGA

Type 5occasional

Old ports: PS/2, COM and LPT

How to spot it:

'Round 6-pin', 'legacy', 'RS-232' or '25-pin'.

Method

PS/2 is a round 6-pin socket for keyboard and mouse.
COM (RS-232) is the serial port.
LPT is the 25-pin parallel printer port.
Match the shape or pin count to the port.

Why it works:

These ports are old, but exams still ask their names.

Try this

Which port was used for the keyboard and mouse of old PCs?

Show solution

It is a round 6-pin socket.
That is the PS/2 port.

Answer

PS/2

Shortcuts that save time

⚡ Serial is a single lane

Serial sends one bit at a time over few wires. It suits long distance. Parallel sends a whole byte across 8 wires. It suits short distance, like old printers.

Example

Which port transmits one bit at a time?

Show solution

One bit at a time means a single lane.

Answer

Serial port

⚡ VGA or HDMI

VGA carries video only and is analog with 15 pins. HDMI is digital and carries audio and video together. 'Sound and picture together' means HDMI.

Example

Which port carries digital audio and video?

Show solution

VGA has no audio.
HDMI carries both.

Answer

HDMI

Mistakes to avoid

Where most students lose marks on this subtopic.

Mistake 01

Saying a serial port sends 8 bits at once.

Serial sends 1 bit at a time. Parallel sends 8 bits.

Mistake 02

Choosing VGA for a stem that mentions sound.

VGA is video only. HDMI or DisplayPort carries audio too.

Mistake 03

Thinking VGA is digital.

VGA is analog. HDMI and DisplayPort are digital.

Mistake 04

Saying you must restart to plug in USB.

USB is hot-swappable. You plug it in while the computer runs.

Mistake 05

Confusing the Ethernet port with the audio jack.

Ethernet (RJ-45) is the wide socket for the network cable. The 3.5 mm jack is for sound.

Quick revision

Read this the night before the exam.

Serial: 1 bit at a time, long distance (COM). Parallel: 8 bits at once, printers (LPT).
HDMI is digital audio and video. VGA is analog video only.
Ethernet (RJ-45) is for the network. PS/2 is old keyboard and mouse. 3.5 mm is audio.
USB is hot-swappable and supplies power (5 V).
USB 2.0 is about 480 Mbps. USB 3.0 is about 5 Gbps.

Practice: 15 questions

Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.

Topic test · 10 questions

Suggested time 4 min · wrong answers go to your mistake notebook automatically.

Continue learning