A computer and its logic gate

A computer and its logic gate

    

A computer and its logic gate :

Computer is an electronic device.  It is mainly used for performing mathematical and logical operations.  Due to being an electronic device, all the digit numbers and statements in the computer are expressed in the form of electronic signal.  For example, we write all the numbers like 250,370, 480 etc. on paper as we have written here, but these numbers are not written in this way inside the computer.  They are expressed as electronic signals.  Similarly, some statements like, Ram is 25 years old or Sheela will not go to school today, etc. We write them very easily on paper.  But in computers, they are written as electronic signals only.  Now the question arises as to what type of electronic signal are there?  There are two types of electronic signals:

 (i) Electronic current. 

(ii) Absence of electronic current.                                                                                                                                                                                                                                  

 Note that in computer language, electronic current is also called pulse.  Day by day, simply writing numbers on paper and doing mathematical operations on them is not a difficult task.  We are well aware of the ease with which they are done.  But by expressing these numbers in the form of electronic pulse inside the computer, it seems difficult to make various calculations on them.  Note that even though we find this task difficult, it is very easy for a computer.  There are special types of electronic circuits in the computer for performing calculations and logical operations by electronic pulse.  These circuits are called logic gates in computer language.

But the gates take all numbers or statements as electronic pulse and by calculation they provide results in the form of electronic pulse.

 what are logical gates, what are their characteristics and what kind of results they provide, etc.  Things are described in this chapter.

Introduction to Logic Gates :

 Logic gates are specific types of electronic circuits that function based on the following two states of current:

 (1) presence of electronic current

 (ii) absence of electronic current. 

 The presence of electronic current in the logic gates is addressed by 1 and its absence by 0.  Hence it can be said that the logic gates take 0 and 1 data and also give the output as 0 and 1.

Types of Logic Gates Logic

 Gates are basically of the following three types:

 (i) AND gate (AND gate)

 (ii) and gate (OR gate) 

(iil) NOT gate

 Other gateways used in computers are  Gates are made by  These three types of gates are discussed in detail below.

AND GATE

The AND gate takes two inputs and gives one output.  The end gate is always represented by the symbol shown here.  This gate has the following characteristics:

(i) If the first input is 0 and the second input is also 0, then it gives 0 to the output.

(ii) If the first input is 1 and the second input is 0, then it gives 0 to the output.

(iii) If the first input is 0 and the second input is 1, then it gives 0 in the output.

(iv) If the first input is 1 and the second input is also then it gives 1 in the output.  Based on the above characteristics of end gate, it can be said that end gate gives output only when both of its inputs are 1.

Examples :

Truth Table of End Gate :

When, for a gate, all types of inputs and their outputs are shown in the form of a table, then that table is called Truth Table of that gate.  The truth table of the end gate is shown below.

AND GATE :

And the gate takes two inputs and returns one output. This gate is always indicated by the symbol shown here. This gate has the following characteristics

(i) If the first input is 0 and the second input is also 0, then it gives 0 in the output.

(ii) If the first input is 1 and the second input is 0, then it gives 1 at the output 

(iii) If the first input is 0 and the second input is 1 it gives 1 at the output.

(iv) If the first input. And the second input as well.

 So it gives 1 in the output and based on the above characteristics of the gate it can be said that AND gate gives 0 output only when both its inputs are 0.

And the Truth Table of the Gate :

When for a gate, all types of inputs and the outputs they represent are represented as a table, that table is called the Truth Table of that gate.

And the truth table of the gate is shown below.

Not Gate :

 Not Gate takes only one input and returns one output.  The symbol used for the knot gate is shown here in the figure.  The NOT gate has the following characteristics:

(i) If the input is 0 then a 1 is obtained at the output. 

(ii) If the input is 1 then the output is 0.  On the basis of the above characteristics, it can be said that it reverses whatever input is given to the notched gate.

Truth Table of Not Gate :

When all types of inputs and outputs for a gate are represented as a table, that table is called the Truth Table of that gate. The Truth Table of the Not Gate is shown below .

Some other gates of computer :

You are familiar with AND, AND AND NOT gate of computer and know that these gates are basic gates.  Many other gates are made by combining these gates.  The following two popular gates are constructed by combining End and Not Gate:

(i) Nend Gate

(ii) Naur Gate 

The introduction of these two gates is given further.

Nand Gate :

Nand Gate is formed by combining End and Not Gate.  In NAND gate, the output of AND gate is given to the input of NOT gate, which reverses it.

  NAND gate has the following characteristics

(i) it gives 1 in output if first input is 0 and second input is also 0 

(ii) it outputs if first input is 1 and second input is 0.  Gives 

(iii) If the first input is 0 and the second input is 1 then it gives 1 in the output.

(iv) If the first input is 1 and the second input is also 1, it gives 0 in the output.

 Based on the above characteristics of NAND gate, it can be said that NAND gate gives 0 output only when both its inputs are 1.

Nand Gate Truth Table :

When for any gate .  All types of inputs and their outputs are shown in the form of a table, then that table is called the truth table of that gate. 

  The truth table of Nand Gate is shown below .

Nor Gate :

Nor Gate is formed by combining Nor Gate and Knot Gate.  In the NOR gate, the output of the AND gate is passed to the input of the NOR gate, which inverts it.

Nor gate has the following characteristics -

(i) If the first input is 0 and the second input is also 0 then it outputs.  gives .  

(ii) If the first input  and second input is 0 then it gives 0 in output.  

(iii) If the first input is 0 and the second input is 1 then it gives 0 in the output.  

(iv) If the first input is 1 and the second input is also 1, it gives 0 in the output.  

On the basis of the above charactics of the nor gate it can be said that the nor gate gives 1 output only when both its input are 0.

Truth Table of Nor Gate :

When, nor a gate, all types of inputs and their outputs are shown in the form of a table, then that table is called the truth table of that gate.  The truth table of Nor Gate is shown below.

Other gates are prepared by various combinations of the above gates, these gates perform mathematical and logical operations.  Note that all these gates are contained in the CPU of the computer:

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