Class 11 Number System and Boolean Logic Notes for NEB

Class 11 number system and Boolean logic notes should teach you how to solve and verify problems, not only memorize completed tables. Match the depth and terminology to the current NEB/CDC curriculum used by your school.

Number systems

A number system uses a base and permitted digits. Decimal uses base 10, binary base 2, octal base 8 and hexadecimal base 16.

Converting to decimal

Multiply each digit by the corresponding power of the base and add the results. Check the position of the radix point carefully.

Converting from decimal

For whole numbers, use repeated division by the target base and read remainders in reverse. For fractions, use repeated multiplication and record integer parts.

Binary, octal and hexadecimal shortcuts

Group binary digits in threes for octal and fours for hexadecimal, adding leading or trailing zeros only where their place value does not change the number.

Binary arithmetic

Practise addition and subtraction one position at a time while recording carry or borrow. Verify the answer by converting both sides to decimal.

Boolean logic

Boolean variables have two states. Operations such as AND, OR and NOT combine or invert conditions. Learn the symbol, verbal meaning and truth table together.

Truth-table method

Count the input variables.
Create every input combination.
Evaluate smaller subexpressions first.
Complete the final output column.
Compare against the expected gate behavior.

Logic gates

Connect each gate to its Boolean operation. NAND and NOR are called universal because circuits for other operations can be built from them. Study derived gates only to the level required by your course.