Karnaugh Map (K-Map):
One variable, two variable, three variable, four variable:
Representation of truth table on karnaugh map:
Plot k-map fot the expression:
Y = (A+ B+ C+`D) (A+`B+`C+ D) (A+
B+`C+`D) (`A+`B+ C+ D) (`A+`B+`C+ D)

Grouping 2 adjacent cell:
Y=`A`B`C D + A`B`C D
= `B`C D (`A + A ) {RULE `A + A=1}
= `B`C D
Y=`A`BC+`ABC+ABC
=`A`BC+ `ABC+ `ABC+ ABC
=`AC(`B+B)+BC(`A+A) {RULE
=`AC+BC
Grouping 4 adjacent cell:
Y=`AB`CD+ `ABCD+ AB`CD+ ABCD
=`ABD(`C+C) +ABD(`C+C)
=`ABD+ABD
=BD(`A+A)
=BD