Buzz words it requires :
High level overview
High Level Language
↓
Assembly Language
↓
Machine Code
↓
Instruction Format (8-bit / 16-bit / 32-bit)
↓
Stored in Memory (RAM)
↓
CPU reads from Memory and Executes
Now understand how data flowing inside the computer
┌────────────────────┐
│ ROM │
│ (Permanent programs │
│ like BIOS, firmware) │
└────────────────────┘
↓
[ Only at computer startup / boot time used ]
↓
┌────────────────────┐
│ SSD / Hard Disk │
│ (Your source code, │
│ compiled programs │
│ and data stored here) │
└────────────────────┘
↓
[ When you Run Program ]
↓
┌────────────────────┐
│ RAM (Memory) │
│ (Machine code / │
│ Instructions loaded │
│ here temporarily) │
└────────────────────┘
↓
[ CPU reads Instructions from RAM ]
↓
┌────────────────────┐
│ CPU │
│ (Executes Instructions) │
└────────────────────┘
- You Press the Key 'A' on the Keyboard
When you press 'a', it's a mechanical switch being triggered on the keyboard matrix.
Keyboard Matrix + Controller
Keyboards are arranged in a row × column matrix.
When a key is pressed, the intersection of a specific row and column is detected.
This event is captured by the keyboard's internal microcontroller.Key Scan Code Generation
The microcontroller converts the row-column press into a scan code.
For example, pressing 'a' on a QWERTY keyboard generates a scan code like 0x1C.
- Scan Code to ASCII Conversion (by OS/Driver)
The scan code is sent over USB or PS/2 interface to the computer.
- The keyboard driver inside the OS (like Windows/Linux) receives it.
The driver translates it to an ASCII character 'a' (which is 0x61 in ASCII).
7.Interrupt is Triggered to CPU
The keypress triggers an interrupt request (IRQ).
CPU stops its current task and handles the interrupt using an Interrupt Service Routine (ISR).
Character Handling in the OS
The operating system processes this input, usually pushing it into a keyboard buffer.
- This buffer stores keys temporarily for use by applications like editors, shells, etc.
9.Application-Level Input Handling
Say you’re typing in a program like Notepad or a C/C++ program.
The application reads the character 'a' from the buffer using input handling functions (cin, scanf, etc.).
10 .Storing the Value of a Variable
Suppose in C code: a = 9;
Compiler will:
Allocate memory for a (maybe in stack or data section).
Generate an instruction like MOV EAX, 9 → MOV [a], EAX.
- Assembly to Machine Code Translation
MOV EAX, 9 is written in assembly.
During compilation, this gets converted into machine code:
Example: B8 09 00 00 00 → where B8 is opcode for MOV EAX, imm32
- Instruction Execution in CPU
CPU fetches the instruction:
Instruction Register (IR) stores the opcode.
Control Unit (CU) decodes it.
ALU executes it if arithmetic/logical.
The number 9 is placed in the register EAX.
It can then be moved into memory using an address from the stack or data segment.
- Memory Operations
If a is stored in memory:
Address Bus is used to specify the memory address.
Data Bus carries the actual value (9).
On a 32-bit system:
Addresses are 4 bytes wide.
Data is processed in 32-bit registers like EAX, EBX, etc.
Output on Screen
If you later print the value of a:
CPU executes display-related system calls.
These system calls go to the OS kernel.
The OS communicates with the GPU (Graphics Card) using drivers and framebuffer/memory-mapped I/O.
Graphics Rendering
GPU takes characters like '9', draws the glyph using a font rasterizer.
Converts into pixels on the screen using the frame buffer.
Your display controller refreshes the screen 60/75/144 times per second to show updated pixels.
Now once you have data on your device and you belong to india but now how does this data getting transferred to another person who is living in USA ?
Full overview -
It uses osi model .
What is the OSI Model
Everything is Electricity and electriclty contains voltage . These voltage flows + Rules(IEEE, protocol) it gets converted into the internet . It required medium so that data can travel through that medium .
Transmission Media in Computer Networks - GeeksforGeeks
You can understand that if something we can see physically then it is easier to assume something is happening and that’s why data going there because cable is connected . SO internally data is doing conversion of bits and data is getting transfeered with applying some rules .
Light , electricity , radio wireless things are using only these things to data transmitting .
NOw the question is how data going in air ?
Your computer contains NIC Card . Nic card converting your electrical signal to radiowave , microwave , infrared . How ?
It uses the process of modulator and demodulator with frequency and wave , it used to figure out what data is getting flowed .
Example - 01111110 - Let’s say it is letter a .
data → encoding → port → frames → segments → packets -> ip address , mac address
.
your data travels as electricity → radio waves → light pulses → radio waves → electricity, guided by global rules, routers, and undersea fiber cables.
your home → your mobile → connected with router → modem → local ISP → regional ISP → International ISP → Router → regional isp → local isp → model →. router →> connected with another user .
Bits → Oscillating voltage → Antenna → EM wave → Space → Antenna → Tiny current → Bits
Here what i have got from chatgpt:-
This is where physics + networking secretly shake hands.
1️⃣ First truth (very important)
📡 Radio waves are NOT “sent” like objects
They are electromagnetic waves created by moving electric charges
Nothing is thrown.
Nothing travels inside the antenna.
👉 Energy + oscillation = wave
2️⃣ Who defines radio rules?
Wireless devices follow rules made by IEEE (Wi-Fi, Bluetooth)
And governments regulate usage via Federal Communications Commission / Telecom Regulatory Authority of India
These rules decide:
Frequency
Power
Modulation
Channel width
3️⃣ Start from the transmitter (real hardware)
Inside your phone / router:
① Data → bits
Hello → 01001000 01100101 ...
② Bits → oscillating electric signal
A chip called RF transmitter:
Converts bits into a rapidly changing voltage
This voltage oscillates millions or billions of times per second
Example:
Wi-Fi: 2.4 GHz → 2.4 billion oscillations/sec
4️⃣ The antenna — the MAGIC happens here ✨
🧠 Antenna = electricity → radio waves converter
How?
Alternating current flows back & forth in metal
Electrons accelerate
Accelerating charge creates:
Electric field
Magnetic field
These fields detach and move outward
That outward moving energy = radio wave
5️⃣ What actually leaves the antenna?
NOT electrons ❌
NOT current ❌
What leaves:
Oscillating electromagnetic field
Moving at speed of light
6️⃣ Visual mental picture
AC current in antenna
↕ ↕ ↕
Electric field changes
⟂
Magnetic field changes
⟂
Self-propagating wave → → →
Electric field ⟂ Magnetic field ⟂ Direction of travel
7️⃣ How information is put into the wave (very important)
This is called modulation
Examples:
Change amplitude (ASK)
Change frequency (FSK)
Change phase (PSK / QAM)
Wi-Fi uses:
OFDM
Meaning:
Data split into many tiny sub-frequencies
Sent in parallel
More speed, less interference
8️⃣ Air is NOT the medium
Big misconception ❌
Radio waves do NOT need air
They travel in:
Air
Vacuum
Space
That’s how:
📡 satellites work
📻 space signals reach Earth
9️⃣ Receiver side (reverse process)
At the receiving antenna:
Incoming wave hits metal
Electric field pushes electrons
Tiny current is induced
Receiver measures:
Phase
Amplitude
Frequency
Bits are reconstructed
🔁 Complete flow (one line)
Bits → Oscillating voltage → Antenna → EM wave
→ Space → Antenna → Tiny current → Bits
🔑 One-sentence memory hack
Radio waves are created when electricity wiggles fast inside an antenna.
10️⃣ Why frequency matters (quick)
Higher frequency:
More data
Less range
More blockage
Lower frequency:
Longer range
Better penetration
Slower data
That’s why:
2.4 GHz → long range
5 GHz → faster
60 GHz → crazy fast, tiny range
what internally port is doing tell me real world example hardware and network both
Great question. Let’s demystify ports properly — not the fake “just a number” answer, but what is actually happening inside hardware + network.
I’ll go step-by-step, like a real mental model you can reuse forever.
1️⃣ First: what a port really is (core idea)
A port is NOT a physical hole.
A port is:
👉 A label used by the OS to decide which program should receive incoming data
That’s it.
No magic. No electricity inside a “port”.
2️⃣ Real-world analogy (best one)
🏢 Big Office Building Example
Imagine:
IP address → Building address
Port number → Room number
Application → Person sitting in that room
Packet → Courier with a letter
Flow:
Courier reaches the building → IP address
Security checks the room number → port
Letter is delivered to the person in that room → application
📌 Without room numbers, security wouldn’t know who should get the letter.
Same in networking.
3️⃣ Network level (what happens on the wire)
Packet actually looks like this:
[ Ethernet ]
[ IP Header ] → which machine?
[ TCP/UDP Header ] → which program?
[ Data ]
Inside TCP/UDP header:
Source Port
Destination Port
Example:
Source IP: 192.168.1.10
Source Port: 54321 (your browser)
Dest IP: 142.250.182.14
Dest Port: 80 (web server)
➡️ Router only cares about IP
➡️ OS cares about port
4️⃣ Inside the OS (this is the important part)
When data reaches your computer:
Step-by-step internally
Network card receives bits
Kernel network stack processes packet
Kernel checks:
Protocol (TCP / UDP)
Destination port
Kernel looks into socket table
Example socket table:
Port 80 → nginx
Port 3000 → node app
Port 22 → ssh
Kernel delivers data to the correct process
📌 Port = key in OS lookup table
5️⃣ Hardware perspective (NIC, CPU, memory)
Let’s be very clear:
❌ Port is NOT:
a wire
a pin
a voltage line
✅ What hardware actually does
NIC (Network Card):
Receives raw bits
DMA copies data into RAM
CPU:
Kernel parses headers
Reads port number
Decides destination process
Memory:
Socket buffers store incoming data
So ports exist as numbers in RAM, not metal.
6️⃣ Why ports are needed (real problem they solve)
Without ports:
Your PC runs:
Browser
Spotify
VS Code
Docker
SSH
All talking to the internet.
❓ Question:
How does OS know which app the incoming data is for?
👉 Answer: Port number
That’s literally the problem ports solve.
7️⃣ Client vs Server ports (important distinction)
Server side
Uses fixed ports
Known in advance
Examples:
80 → HTTP
443 → HTTPS
22 → SSH
Client side
Uses ephemeral ports
Chosen randomly by OS
Example:
Browser → port 53142
Server → port 443
When response comes back:
Dest port: 53142 → browser
8️⃣ Real-world hardware analogy (factory)
🏭 Factory Machine
Factory = Computer
Conveyor belt = Network
Machine ID = Port number
Worker = Process
Raw material arrives → supervisor reads machine ID → sends material to correct machine.
9️⃣ Why same port can’t be used twice
Try running two servers on port 3000:
Error: Address already in use
Why?
Because:
(port, protocol) → must map to ONE process
Otherwise OS won’t know where to deliver data.
🔟 One-line definition (remember this)
A port is an OS-level identifier that tells the kernel which process should receive incoming network data.
11️⃣ If you want, next we can go deeper
I can explain:
How bind() actually reserves a port
What a socket really is internally
How Docker port mapping works internally
How NAT rewrites ports
Why UDP ports behave differently
Just tell me which one you want 👇
what parallel port is doing internallly .
Alright, now we’re talking old-school real hardware 😄
Let’s open the parallel port from the inside — wires, signals, CPU, everything.
1️⃣ What a parallel port really is
A parallel port is a hardware interface where:
👉 multiple data bits are sent at the same time using multiple physical wires
That’s why it’s called parallel.
2️⃣ Physical reality (no abstraction here)
Classic PC parallel port (DB-25 connector) has 25 pins.
Pin breakdown (important)
Type Pins What they do
Data lines 8 Carry actual data (bits)
Control lines ~4 Tell when to send
Status lines ~5 Tell device state
Ground rest Return path
So yes — real copper wires, not numbers.
3️⃣ Real-world analogy (best one)
🧃 Juice Boxes Analogy
Parallel port = 8 juice boxes
Each box = 1 bit
Open all boxes at the same time
If data = 10110010
All 8 bits travel simultaneously.
📌 One electrical pulse per wire.
4️⃣ Internally inside the computer (step-by-step)
Let’s say you print the letter A (01000001).
Step 1: CPU instruction
OUT 0x378, 0x41
0x378 → parallel port data register
0x41 → ASCII for 'A'
Step 2: I/O Controller / Southbridge
CPU sends value to I/O bus
Parallel port controller receives it
Stores value in data register
Step 3: Voltage on pins (this is key)
Bit Pin Voltage
0 D0 0V
1 D1 5V
0 D2 0V
0 D3 0V
0 D4 0V
0 D5 0V
0 D6 0V
1 D7 5V
⚡ Electricity flows on all pins at once
Step 4: Control signal (STROBE)
CPU sets STROBE pin LOW
This tells printer:
“READ DATA NOW”
Step 5: Device reads data
Printer:
Samples all 8 data lines
Latches value into its buffer
Sends ACK signal back
Step 6: CPU continues
ACK pin goes HIGH
OS knows data was received
Next byte sent
5️⃣ What registers exist internally
Parallel port hardware exposes registers:
Register Purpose
Data register Holds 8 bits
Status register Busy, error, ACK
Control register Strobe, init, reset
These registers are mapped to I/O addresses, not RAM.
6️⃣ Timing (why it’s slow)
Even though 8 bits go together:
CPU waits for ACK
Mechanical printers were slow
Lots of handshaking
So speed was limited.
7️⃣ Why it disappeared
Problems:
Thick cables
Noise (crosstalk)
Short distance (~3 meters)
One device at a time
USB solved all of this.
8️⃣ Official standard (for completeness)
Parallel port behavior is standardized under IEEE 1284
It defined:
EPP (Enhanced Parallel Port)
ECP (Extended Capability Port)
9️⃣ One-line internal definition (memorize this)
A parallel port drives multiple physical data lines with voltages simultaneously, coordinated by control and status signals, directly managed by hardware registers.
🔟 Parallel vs Serial (quick contrast)
Parallel Serial
8 wires 1–2 wires
Short distance Long distance
Hardware heavy Software + hardware
Old printers USB, Ethernet
If you want next:
Parallel vs USB internal comparison
How serial beats parallel despite fewer wires
Why CPU OUT instruction can control hardware
How BIOS used parallel ports
Just say the word 👇
i didn't understand still . tell me with example like i send hello world then how physicall port sending playing rule full indepth
Perfect 👍
You’re not dumb — this topic is confusing because people skip the physical story.
So now I’ll do ONE concrete story:
👉 You send "HELLO" to a printer using a parallel port
No theory jumps. No abstraction. Just what happens in real life, on wires.
🧠 Goal
You type:
HELLO
Printer prints:
HELLO
We’ll follow one letter first (H), then the rest repeats.
1️⃣ Before anything happens (physical setup)
Real physical things that exist
PC
Parallel cable (thick cable)
Printer
Inside cable:
8 data wires
control wires
status wires
ground wires
These are real copper wires.
2️⃣ What is inside your PC (important)
Inside motherboard:
Parallel Port Controller chip
It has:
Data Register (8 bits)
Control Register
Status Register
CPU can write numbers to these registers.
3️⃣ You press Print → OS sends data
The OS converts:
"H" → ASCII → 72 → binary → 01001000
4️⃣ CPU writes to parallel port (this is NOT software now)
CPU executes an instruction like:
OUT data_register, 01001000
💥 This is where physics starts
5️⃣ What happens inside the parallel port hardware
The controller:
Takes 01001000
Stores it in Data Register
Immediately:
Wire Bit Voltage
D0 0 0V
D1 0 0V
D2 0 0V
D3 1 5V
D4 0 0V
D5 0 0V
D6 1 5V
D7 0 0V
⚡ Electric current flows
⚡ All 8 wires change voltage at the same time
This is the parallel part.
6️⃣ But printer doesn’t read yet (important rule)
Printer is just watching wires.
It waits for STROBE signal.
7️⃣ CPU tells printer: “READ NOW”
CPU sets STROBE control pin LOW.
This means:
📢 “Data on wires is valid! Read it!”
This is a rule of the parallel port.
8️⃣ What printer physically does
Inside printer electronics:
Detects STROBE falling edge
Samples voltages on all 8 data wires
Converts voltages → bits → 01001000
Stores byte in its buffer
Raises ACK signal
9️⃣ ACK signal goes back (reverse direction)
Printer sends voltage on ACK wire.
PC sees:
“Printer received the byte”
This is how handshaking works.
🔁 Repeat for each character
Now same steps for:
Letter Binary
E 01000101
L 01001100
L 01001100
O 01001111
Each letter:
8 wires change voltage
STROBE goes LOW
Printer reads
ACK comes back
🔟 End of line (HELLO printed)
Printer firmware:
Converts ASCII → dots
Moves motors
Sprays ink / hits ribbon
Prints HELLO
🔥 VERY IMPORTANT: what the port is “doing”
The parallel port itself is NOT thinking
It is ONLY:
Setting voltages on wires
Reading voltages on wires
Following fixed electrical rules
🧠 The golden mental picture (remember this)
Parallel port = 8 light switches + a doorbell
Switches = data wires
Doorbell = STROBE
ACK = “I heard you”
🧠 Why this is called a PORT
Because:
CPU can send numbers
Hardware converts numbers → voltages
Device reads voltages → numbers
It’s a door between software and electricity.
⚠️ Common misunderstanding (you may have this)
❌ “HELLO goes directly in wire”
✅ Only voltages go in wire
Letters exist only in human brain & software.
🎯 One-line final truth
Parallel port sends data by putting voltages on multiple wires at the same time and using control signals to tell the device when to read them.
If you want next, I can:
Draw ASCII timing diagram
Explain why noise kills parallel
Compare USB vs parallel with same HELLO example
Explain serial port with same HELLO story
Just tell me 👇
now i am confused how the data is geeting differentiate because there is lot of data is sending so there are so many cable how they going in once cable radiowaves tell me full processs how this handing
Perfect — this confusion is the exact right confusion 👍
It means you’re now touching the core truth of communication systems.
Let’s slow this down and rebuild ONE clean mental movie from many wires → one cable → radio waves → back to data.
No skipping. No magic words.
🧠 The BIG question you’re asking (rephrased)
“If LOTS of data exists, and MANY devices talk, and finally there is ONLY ONE cable or radio wave…
HOW does data not get mixed up?”
This problem is called multiplexing + encoding.
PART A — First truth (very important)
❌ Data does NOT travel as letters, bits, or bytes
✅ ONLY electrical signals or radio waves travel
Everything else is rules.
PART B — Start small: MANY wires → ONE cable (Ethernet)
1️⃣ Parallel port (old days)
8 data wires
1 byte at once
Short distance
Too messy
❌ Doesn’t scale
2️⃣ Modern systems use SERIAL transmission
Instead of:
8 bits at same time
They do:
1 bit → then next → then next → very fast
Example:
HELLO → 01001000 01000101 ...
Sent as:
0 1 0 0 1 0 0 0 0 1 0 0 0 1 0 1 ...
📌 ONE wire, but VERY FAST
PART C — But still… MANY devices, ONE cable 😵
Now comes the real magic.
3️⃣ How MANY data streams share ONE cable
This is solved by multiplexing.
Think of it like rules for sharing.
🎥 Real-world analogy: Talking in a classroom
One air
Many students
How no chaos?
Methods:
Take turns (time)
Speak at different pitches (frequency)
Speak different languages (encoding)
Networks use ALL THREE.
PART D — The 3 main techniques (CORE)
1️⃣ Time Division (TDM)
Each sender gets a time slot.
Time →
[A][B][C][A][B][C]
So data looks like:
A1 B1 C1 A2 B2 C2
📌 Only ONE signal at a time
📌 Very fast switching
2️⃣ Frequency Division (FDM)
Same cable, different frequencies.
Like FM radio:
98.3 MHz → one channel
102.5 MHz → another
Internet cables carry many frequencies at once.
3️⃣ Encoding / Modulation (MOST IMPORTANT)
Bits are turned into wave changes.
Examples:
Voltage level
Phase shift
Frequency shift
PART E — From wire → radio waves (Wi-Fi example)
Let’s take HELLO and send it via Wi-Fi.
4️⃣ Inside your laptop (step-by-step)
Step 1: Bits
HELLO → 01001000 01000101 ...
Step 2: Frames
Data wrapped with:
Sender ID
Receiver ID
Error check
Step 3: Modulation
Bits change the radio wave:
Bit Wave
0 Phase A
1 Phase B
Now data = wave shape
Step 4: Antenna
Electrical signal → oscillating current
Creates electromagnetic waves
Leaves antenna into air
📡 This follows IEEE 802.11
PART F — BUT AIR IS SHARED 😱
How does Wi-Fi avoid chaos?
5️⃣ Wi-Fi rules (simplified)
Listen before talking
If silent → send
If collision → wait random time
Retry
This is called CSMA/CA
PART G — Receiver side (reverse process)
Router receives wave:
Antenna converts wave → electrical signal
Decoder extracts bits
Error check
Uses address to decide:
“Is this for me?”
Others ignore it.
PART H — Why data doesn’t mix
Because EVERY packet has:
Sender address
Receiver address
Sequence number
Error checksum
So even if signals overlap:
Garbage is detected
Packet is dropped
Retransmission happens
PART I — ONE cable carrying EVERYTHING (Ethernet / Fiber)
That single cable carries:
Netflix
YouTube
SSH
GitHub
Because:
Time slots
Frequencies
Encoded frames
Addresses
Ethernet rules come from IEEE 802.3
🧠 FINAL MENTAL MODEL (LOCK THIS IN)
Data is chopped into tiny pieces, encoded as signal changes, shared by time & frequency, sent as waves, and reassembled using strict rules.
⚡ One killer sentence (remember forever)
Many data streams don’t mix because communication is rule-based, not free-form.
If you want next, I can:
Draw a signal timeline
Explain fiber optics with same logic
Show how router decides packet ownership
Explain why noise doesn’t kill the internet
Just say 👍
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