Computer • Chapter 04

Logic Gate

लॉजिक गेट
Digital Circuits • Gate Types • Truth Tables • Applications • Exam Revision
Source: uploaded Computer PDF — Chapter 4, PDF pages 15–18. Source wording/tables are retained; internal print inconsistencies are explicitly flagged.
0 & 1
Binary Inputs
1 Output
One or more inputs
NAND / NOR
Universal Gates in source
7 Types
AND, OR, NOT, NAND, NOR, XOR, XNOR
⚙ Introduction to Logic Gates / लॉजिक गेट्स का परिचय
  • Logic gates are the basic building blocks of digital circuits.
  • They perform logical operations based on binary inputs (0 & 1).
  • Used in computers, automation and electronic circuits.
  • A logic gate can take one or more inputs, but the output will be one.
  • The PDF states that a logic gate is used to allow or deny a digital signal.
  • The PDF states that logic gates are made up of diodes and transistors.
LOGIC GATESलॉजिक गेट BASICAND • NOT • OR UNIVERSALNAND • NOR OTHEREX-OR • EX-NOR
Logic gates classification and source symbols from PDF page 15
PDF visual • Gate classification with Buffer/Inverter/AND/NAND symbols and source truth tables (page 15)

Basic Logic Gates

ANDNOTOR

Universal Logic Gates

NANDNOR

Other Logic Gates

EX-OR / XOREX-NOR / XNOR
AND Gate
Source rule: output is 1 only if both inputs are 1.
A · B
OR Gate
Source symbol: A + B. The printed rule line conflicts with the printed OR truth table; see source note below.
A + B
NOT / Inverter
Page 15's inverter visual shows a single input changed to its opposite output.
0→1 • 1→0
NAND Gate
Source: opposite of AND; output is 0 only when both inputs are 1.
(A · B)̅
NOR Gate
Source: opposite of OR; output is 1 only if both inputs are 0.
(A + B)̅
XOR Gate
PDF labels this section “XOR”; its printed rule and some printed tables conflict with each other.
A ⊕ B
XNOR Gate
Source rule on page 18: output is 1 if inputs are same.
(A ⊕ B)̅
SOURCE PRINT NOTE
The PDF contains multiple internal label/rule/table inconsistencies in this chapter. This mind map does not silently replace those lines with outside knowledge; the source wording is retained and conflicts are flagged where they occur.
OR NOR XOR XNOR symbols from PDF page 16
PDF visual • OR, NOR, XOR and XNOR symbols with the tables printed on page 16
AND — Source Truth Table
ABA·B
000
010
100
111
SOURCE RULE
Output is 1 only if both inputs are 1.
OR — Source Truth Table
ABA+B
000
011
101
111
PDF INCONSISTENCY
The OR section's printed rule says “Inverts the input (0→1, 1→0)” while its printed truth table above is different. Both are preserved as source evidence.
NAND — Source Truth Table
AB(A·B)̅
001
011
101
110
SOURCE RULE
Opposite of AND; output is 0 only if both inputs are 1.
NOR — As Printed on Page 17
AB(A+B)̅
001
010
101
110
PDF INCONSISTENCY
The source rule says output is 1 only if both inputs are 0, but the printed page-17 row for A=1, B=0 shows output 1. This is left as printed and flagged.
XOR — Source Section
ABA⊕B
000
011
101
110
PDF INCONSISTENCY
The printed XOR heading says “Exclusive NOR” and the printed rule says “Output is 1 if inputs are same,” while the table printed immediately below is 0,1,1,0.
XNOR — Source Truth Table
AB(A⊕B)̅
001
010
100
111
SOURCE RULE
Output is 1 if inputs are same.
NOT Gate Label on Page 17

The PDF prints the heading “NOT Gate (NOT गेट) – Universal Gate”, but the rule/table placed under that heading are the same pattern printed for NAND immediately below it. This is treated as a source-layout inconsistency, not silently repaired.

XNOR truth table from PDF page 18
PDF visual • XNOR gate source truth table (page 18)
🧩 Applications of Logic Gates / लॉजिक गेट्स के उपयोग
  • Used in computer processors & circuits.
  • Used in alarm systems & security devices.
  • Used in automatic gates & digital locks.
  • Used in artificial intelligence (AI) and robotics.
Digital Building Block

The chapter frames logic gates as the basic building blocks that perform logical operations on binary 0/1 inputs.

Input → Output Idea

One or more inputs can be accepted, while the output remains a single digital result.

⚡ Quick Recall
  • Logic gates: basic building blocks of digital circuits.
  • Inputs: binary 0 and 1.
  • Basic gates in source: AND, NOT, OR.
  • Universal gates in source: NAND, NOR.
  • Other gates: EX-OR and EX-NOR.
  • AND source table: only 11 gives 1.
  • NAND source table: only 11 gives 0.
  • XNOR source table: same inputs (00, 11) give 1.
EXAM TRAP / SOURCE ALERT
This PDF chapter has internal typos/inconsistencies around OR, NOT, NOR and XOR labels/rules/tables. For this source-based mind map, they are flagged instead of silently corrected.