What is a Network Interface Card(NIC)?

A Network Interface Card (NIC) is a hardware component that allows a
computer or device to connect to a network and communicate with other
devices.

NIC = A hardware component that enables a device to send and receive
data over a network, either by cable (wired) or wirelessly.

Also called a network adapter or network card.

Every device that connects to a network must have a NIC.

The NIC handles the conversion of data between the computer and the network.

Modern NICs are usually built directly into the motherboard.

2. Types of NIC

🔌 Wired NIC (Ethernet NIC)

Connects the device to a network using an Ethernet cable (RJ45 connector).

Provides a stable, fast, and secure connection.

The cable plugs into the RJ45 port on the NIC.

Common in desktop computers, servers, and gaming setups.

📶 Wireless NIC (Wi-Fi NIC)

Connects the device to a network using radio waves (Wi-Fi).

No physical cable required.

Communicates with a wireless access point or router.

Built into virtually all laptops, smartphones, and tablets.

External wireless NICs are available as USB dongles.

3. What Does a NIC Do?

A NIC performs several important functions to enable network communication:

Key Functions of a NIC

Function	Description
Data conversion	Converts digital data from the computer into signals for the network
MAC addressing	Each NIC has a unique MAC address to identify it on a network
Data transmission	Sends data packets onto the network medium
Data reception	Receives incoming data packets from the network
Error checking	Checks received data for errors during transmission
Speed control	Manages the speed of data transfer (e.g. 100 Mbps, 1 Gbps)

4. The MAC Address

Every NIC has a unique identifier called a MAC address
(Media Access Control address).

MAC Address = A unique 48-bit hardware address permanently assigned
to a NIC by its manufacturer.

Written as 6 pairs of hexadecimal digits, separated by colons or hyphens.

Example: A3:B2:C1:D4:E5:F6

The first 3 pairs identify the manufacturer.

The last 3 pairs identify the specific device.

MAC addresses operate at the data link layer of a network.

Used to identify devices within a local network (LAN).

MAC Address vs IP Address

Feature	MAC Address	IP Address
What it identifies	The physical NIC hardware	The device on a network
Assigned by	Manufacturer (permanent)	Network / Router (can change)
Changes?	❌ No — fixed at manufacture	✅ Yes — can be dynamic
Used on	Local network (LAN)	Local and wide area networks
Format	48-bit hexadecimal	32-bit (IPv4) or 128-bit (IPv6)
Example	`A3:B2:C1:D4:E5:F6`	`192.168.1.1`

5. How a NIC Sends and Receives Data

Sending Data

Receiving Data

6. NIC Speeds

NICs operate at different speeds depending on the type and standard:

NIC Type	Speed
Fast Ethernet NIC	100 Mbps
Gigabit Ethernet NIC	1 Gbps (1000 Mbps)
10 Gigabit NIC	10 Gbps
Wireless (Wi-Fi 5)	Up to 3.5 Gbps (theoretical)
Wireless (Wi-Fi 6)	Up to 9.6 Gbps (theoretical)

Mbps = Megabits per second | Gbps = Gigabits per second

7. Wired NIC vs Wireless NIC — Comparison

Feature	Wired NIC	Wireless NIC
Connection medium	Ethernet cable	Radio waves
Speed	Faster and more consistent	Slower, affected by interference
Reliability	Very reliable — no interference	Subject to signal interference
Security	More secure — physical access needed	Less secure — signal can be intercepted
Portability	Limited — cable restricts movement	Full freedom of movement
Setup	Requires cable infrastructure	Easier — no cables needed
Typical use	Desktops, servers, gaming	Laptops, phones, tablets

8. Where is the NIC Found?

Most modern laptops and desktops: NIC is integrated directly onto the motherboard.

Older or specialised desktops: A separate NIC expansion card is inserted into a PCIe slot.

Adding wireless to a desktop: A USB wireless NIC dongle can be plugged in.

Smartphones/tablets: NIC functionality is part of the System-on-Chip (SoC).

9. NIC in the Context of a Network

Every device on the network has its own NIC with its own MAC address.

The switch uses MAC addresses to direct data to the correct device.

The router connects the local network to the internet.

10. Key Vocabulary

Term	Definition
NIC	Network Interface Card — hardware that connects a device to a network
MAC Address	A unique 48-bit hardware address permanently assigned to a NIC
Ethernet	A standard for wired network communication using cables
RJ45	The connector type used for Ethernet cables
Wi-Fi	Wireless network communication using radio waves
Packet	A small unit of data transmitted across a network
Data Link Layer	The network layer where MAC addresses operate
Network Adapter	Another name for a NIC
USB Dongle	A small external wireless NIC plugged into a USB port
Bandwidth	The maximum rate of data transfer across a network connection

11. Exam Tips ✅

A NIC is required for every device that connects to a network —
without it, no network communication is possible.

Know the difference between a MAC address (hardware, permanent,
set by manufacturer) and an IP address (logical, can change,
assigned by network).

A MAC address is written in hexadecimal — be prepared to
recognise this format in exam questions.

Know the difference between wired (Ethernet) and wireless (Wi-Fi)
NICs — their advantages and disadvantages are commonly tested.

The switch uses MAC addresses to direct traffic —
this links the NIC topic to network hardware topics.

Modern NICs are almost always integrated into the motherboard —
separate expansion cards are less common but still exist.

A common exam question: "What is the purpose of a NIC?"
→ To connect a device to a network and enable it to send and receive data.

Cambridge (CIE) IGCSE Computer Science — 0478 / 0984

2. Types of NIC#

🔌 Wired NIC (Ethernet NIC)#

📶 Wireless NIC (Wi-Fi NIC)#

3. What Does a NIC Do?#

Key Functions of a NIC#

4. The MAC Address#

MAC Address vs IP Address#

5. How a NIC Sends and Receives Data#

Sending Data#

Receiving Data#

6. NIC Speeds#

7. Wired NIC vs Wireless NIC — Comparison#

8. Where is the NIC Found?#

9. NIC in the Context of a Network#

10. Key Vocabulary#

11. Exam Tips ✅#