Editing Channel Coding (section)

== <span style="color: #FFFFFF;">Applying</span> ==
'''Modeling 'The Parity Bit' (Simple error detection):'''
<syntaxhighlight lang="python">
def add_parity_bit(data_string):
    """
    Adds a '1' if the number of ones is odd, to make it 'Even Parity'.
    """
    ones_count = data_string.count('1')
    parity = '1' if ones_count % 2 != 0 else '0'
    return data_string + parity

def check_parity(packet):
    """
    Returns True if the parity is still even.
    """
    return packet.count('1') % 2 == 0

# Sender sends '101'
original = "101"
sent = add_parity_bit(original)
print(f"Sent Packet: {sent}")

# Receiver hears '111' (Middle bit flipped by noise)
received = "1110" 
if not check_parity(received):
    print("ERROR DETECTED: The parity doesn't match!")
</syntaxhighlight>

; Coding Landmarks
: '''Hamming Codes (1950)''' → The first code that could not only detect an error but pinpoint exactly which bit was wrong and flip it back.
: '''Reed-Solomon Codes (1960)''' → The code that made "Digital Media" possible. Without it, a single speck of dust on a CD would make it unplayable.
: '''The Voyager Probes''' → Use advanced channel coding to send photos from the edge of the solar system using a transmitter that has less power than a lightbulb.
: '''QR Codes''' → These contain enough "Error Correction" that you can rip a corner off the paper or spray-paint over part of the code and it will still work.
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