Day 2 (Delayed Post) — UGC NET Computer Science from Zero: After 13 Years Gap
(Yesterday I said Day 2 will be Logic Gates — but I posted K-Maps first by mistake. So here is my Day 2! 😊)
Topic: Logic Gates — The Building Blocks of Computer
After MCA 2012, I forgot everything. Starting again from zero for UGC NET Dec 2025.
What I learned today in simple words:
AND Gate: Output 1 only when BOTH inputs are 1. Like 2 keys needed to open a locker.
OR Gate: Output 1 when ANY input is 1. Like 1 key is enough.
NOT Gate: Opposite. 0 becomes 1, 1 becomes 0. Used as Inverter.
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NAND Gate: AND + NOT. Called UNIVERSAL GATE.
NOR Gate: OR + NOT. Also UNIVERSAL GATE.
(Both NAND & NOR are universal because we can make all other gates from them. UGC NET asks this every year!)
XOR Gate: Output 1 when inputs are DIFFERENT. Used in Adders.
XNOR Gate: Output 1 when inputs are SAME. Opposite of XOR.
My trick to remember truth tables:
AND = Multiply (0*1=0)
OR = Add (0+1=1)
NOT = Ulta
I am learning in public, not as an expert. If I can understand after 13 years, you can too!
Day 1: Number System ✅
Day 2: Logic Gates ✅ (Today — late post)
Day 3: K-Map ✅ (Already posted)
Next: 3-Variable K-Map
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