Logic gates , Digital Computer and Analog Computer

Analog Computers Work on continuous values.	Digital computers Work on discrete values.
Analog Computers have low memory.	Digital computers have a very large memory
Analog computers have Slow speed.	Digital computers have fast speed.
Analog computers are less reliable.	Digital computers are more reliable.
Analog computers used in engineering and science and medical fields.	Digital computers are used in all fields of life.
Analog computers are used to calculate / measure analog quantities like speed and temperature.	Digital computers are used to calculate mathematical and logical operations. It can solve addition, subtraction, division, multiplication and other mathematical and statistical operations.
Analog computers provide less accurate results.	Digital computers provide 100% accurate results.
Normally Analog Computers are specific purpose	Digital Computers are general purpose
Analog computers are difficult to use	Digital computers are easy to use
Examples of Analog computers are: thermometer, analog clock, speedometer etc.	Examples of digital computers are: Personal Computer, laptops, smart phones etc.

DIFFERENCE BETWEEN THE HIGH AND THE LOW LEVEL LANGUAGE:

1. Low level language is machine readable form of program. Whereas the high level language will be in human readable form..
2. Low level language are difficult to write and compile but high level languages are easy to write as well as compile..
3. Low level language are compact and require less memory space.. High level language uses compilers and interpreters which requires large memory space.
4. In high level language debugging ( troubleshooting) .I.e. Finding and correcting errors are easier whereas debugging in the low level language is quite difficult.
5. low level language coding and compiling is time consuming process whereas high level language coding and compiling is much easy and takes veryless time to compile.

Compiler : It's a computer program(s) that transforms source code written in a programming language into machine language that is the target language which usually has a binary form known as object code.

Interpreter : It translates high level instructions into an intermediate form, it translates the code into the intermediate form line by line an caries out specific actions.

Assembler : It is a program that takes basic computer instruction(s) and converts then into a pattern of bits that the computer's processor can use to perform it's basic operations. The language used to program the assembler is called assembly language.

Computer Logical Organization - Overview

In the modern world of electronics, the term Digital is generally associated with a computer because the term Digital is derived from the way computers perform operation, by counting digits. For many years, the application of digital electronics was only in the computer system. But now-a-days, digital electronics is used in many other applications. Following are some of the examples in which Digital electronics is heavily used.

• Industrial process control
• Military system
• Television
• Communication system
• Medical equipment
• Radar
• Navigation

Signal

Signal can be defined as a physical quantity, which contains some information. It is a function of one or more than one independent variables. Signals are of two types.

• Analog Signal
• Digital Signal

Analog Signal

An analog signal is defined as the signal having continuous values. Analog signal can have infinite number of different values. In real world scenario, most of the things observed in nature are analog. Examples of the analog signals are following.

• Temperature
• Pressure
• Distance
• Sound
• Voltage
• Current
• Power

Graphical representation of Analog Signal (Temperature)

The circuits that process the analog signals are called as analog circuits or system. Examples of the analog system are following.

• Filter
• Amplifiers
• Television receiver
• Motor speed controller

Disadvantage of Analog Systems

• Less accuracy
• Less versatility
• More noise effect
• More distortion
• More effect of weather

Digital Signal

A digital signal is defined as the signal which has only a finite number of distinct values. Digital signals are not continuous signals. In the digital electronic calculator, the input is given with the help of switches. This input is converted into electrical signal which have two discrete values or levels. One of these may be called low level and another is called high level. The signal will always be one of the two levels. This type of signal is called digital signal. Examples of the digital signal are following.

• Binary Signal
• Octal Signal
• Hexadecimal Signal

Graphical representation of the Digital Signal (Binary)

The circuits that process the digital signals are called digital systems or digital circuits. Examples of the digital systems are following.

• Registers
• Flip-flop
• Counters
• Microprocessors

Advantage of Digital Systems

• More accuracy
• More versatility
• Less distortion
• Easy communicate
• Possible storage of information

Comparison of Analog and Digital Signal

S.N.	Analog Signal	Digital Signal
1	Analog signal has infinite values.	Digital signal has a finite number of values.
2	Analog signal has a continuous nature.	Digital signal has a discrete nature.
3	Example of analog signal − sine wave, triangular waves	Example of digital signal − binary signal.
	.

Digital System, Digital age etc...

Computer architecture

In computer science and engineering, computer architecture is the art that specifies the relations and parts of a computer system. Computer architecture is different than the architecture of buildings, the latter is a form of visual arts while the former is part of computer sciences. In both instances, a complete design has many details, and some details are implied by common practice. For example, at a high level, computer architecture is concerned with how the central processing unit acts and how it uses computer memory. Some fashionable computer architectures include cluster computing and Non-Uniform Memory Access. Computer architects use computers to design new computers. Emulation software can run programs written in a proposed instruction set. While the design is very easy to change at this stage, compiler designers often collaborate with the architects, suggesting improvements in the instruction set. Modern emulators may measure time in clock cycles: estimate energy consumption in joules, and give realistic estimates of code size in bytes. These affect the convenience of the user, the life of a battery, and the size and expense of the computer's largest physical part: its memory. That is, they help to estimate the value of a computer design.

Cluster computing or High-Performance computing frameworks is a form of computing in which bunch of computers (often called nodes) that are connected through a LAN (local area network) so that, they behave like a single machine. A computer cluster help to solve complex operations more efficiently with much faster processing speed, better data integrity than a single computer and they only used for mission-critical applications.

LOGICAL GateLogical Gat

Logic gates are the basic building blocks of any digital system. It is an electronic circuit having one or more than one input and only one output. The relationship between the input and the output is based on a certain logic. Based on this, logic gates are named as AND gate, OR gate, NOT gate etc.

AND Gate

A circuit which performs an AND operation is shown in figure. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

OR Gate

A circuit which performs an OR operation is shown in figure. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

NOT Gate

NOT gate is also known as Inverter. It has one input A and one output Y.

Logic diagram

Truth Table

NAND Gate

A NOT-AND operation is known as NAND operation. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

NOR Gate

A NOT-OR operation is known as NOR operation. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

XOR Gate

XOR or Ex-OR gate is a special type of gate. It can be used in the half adder, full adder and subtractor. The exclusive-OR gate is abbreviated as EX-OR gate or sometime as X-OR gate. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

XNOR Gate

XNOR gate is a special type of gate. It can be used in the half adder, full adder and subtractor. The exclusive-NOR gate is abbreviated as EX-NOR gate or sometime as X-NOR gate. It has n input (n >= 2) and one output.

Logic diagram

Truth Table

Digital Logic Gate Truth Table Summary

The following logic gates truth table compares the logical functions of the 2-input logic gates detailed above.

Inputs		Truth Table Outputs For Each Gate
B	A	AND	NAND	OR	NOR	EX-OR	EX-NOR
0	0	0	1	0	1	0	1
0	1	0	1	1	0	1	0
1	0	0	1	1	0	1	0
1	1	1	0	1	0	0	1