Binary System and ALU Logic Operation


Analog Value

Analog quantity has continuous values.Most of the things in nature appear in analog form. Temperature never goes from 30 to 31 instantly.It takes infinite steps. If we draw a graphical representation, it will give us a continuous curve waveform.

Digital Value

Digital quantity has discrete values.It takes finite steps. If we draw a graphical representation, it will give us a discrete waveform.

  • Digital data can be processed efficiently.
  • Can be stored easily due to limited amount of information.
  • Noise does not affect digital data.
  • digital circuits consume low power.

Machine Language

A system of codes directly understandable by a computer’s CPU is termed as machine language. Machine language is composed only of the two binary digits 0 and 1.


It is a software that converts the programming language into machine language.


It is the minimum information that can be handled by a computer. It is not an imaginary thing, it exists physically in the form of voltage levels.In computer circuitry, a bit is represented by voltage levels which are assigned on the basis of circuit type.

Base 2 Number system

  • 02 symbols (0,1)
  • Computer only recognize off and on like a light switch.
  • Instructions and data are composed of only a series of bits.
  • a single bit is represented by a small “b” and a byte is represented by a capital “B”.
  • Four(04) bits form a nybble.
  • Eight(08) bits form a single byte.
  • In computer, we use byte structure to store data.

Computer handles a series of binary numbers (1010100011011011  or on/off) in two forms

  • Data
  • Set of Instructions

Both of these sets are handle by CPU.This on and Off instructions are known as bits.


bit is the minimum information that can be handled by a computer

Arithmetic Logic Unit

The Arithmetic Logic Unit [ALU] performs arithmetic (Addition, Multiplication etc) and logic operations (AND, OR, COMPLEMENT, EX-OR etc) on binary data which is stored in internal registers.Three basic logic operations are

  • AND
  • OR
  • NOT

Logic Gate:

A circuit that performs a logic operation is called a logic gate. Basic logic elements can combined to form complex logic circuits to perform useful operations like, Comparison, code conversion, encoding, decoding, storage, counting and etc…

AND Gate

AND gate produce high output if, all inputs are high.If any one of them is low then it will produce low level voltage.

OR Gate

OR gate produce high output if, any one of the input is high.If both inputs are low then it will produce low output voltage level.

NOT Gate

NOT gate inverts the logic level.

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