How to calculate tax amount?

 Calculate your payable tax based on your total taxable income.

Environment variable What, Why, Where and How?

What is environment variable?

Environment variable is variable which holds the path of the software installed in your machine.

Why do we need to set environment variable?

When we compile and run any program, then machine try to find the required compiler or runtime to perform the action which we have requested. So either we to have to specify the directory of the software library every time with our command or we could set it into an environment variable so machine can automatically pickup the library path from there based on the command.

For example:

We set python variable to compile and execute the Python code.

python = C:\Python\Python27\python.exe

We set the JAVA_HOME for compile and run the Java programs.

JAVA_HOME = C:\Program Files\Java\jdk1.8.0_201 

We set MVN_HOME for maven build.

MVN_HOME = D:\apache-maven-3.6.0\bin 

Instead of creating all these variable we could also just add these library paths in a common user variable PATH and later add PATH variable in system variable CLASSPATH.

How to set environment variable?

Right click on my computer icon and select the properties option.

A new window will be get opened. Now click on the advance system settings

advance-system-settings-environment-variable

Now click on the environment variables button.

environment-variables

Now here you could either add the installed library path under the PATH user variable to you could create a new user variable and later add the newly create variable in CLASSPATH system variable.

environment-variable-paths.JPG

References:

• https://www.java.com/en/download/help/path.xml
• https://www.computerhope.com/jargon/e/envivari.htm
• https://john-dugan.com/path-variable-in-windows/ 
• https://study.com/academy/lesson/what-are-environment-variables-definition-examples.html

Why we need Python to run Node.js?

Node.js is written on c++, and is build on GYP. GYP is a Meta-Build system: a build system that generates other build systems and help us to build the large project that needs multiple platform to build. GYP is developed and written using Python, so to build and run few modules of Node.js we need Python.

Therefore wherever we need node-gyp to build any node module, Python will be required.

References: 

• https://gyp.gsrc.io/
• https://nodejs.org/en/docs/
• https://github.com/nodejs/node-gyp
• https://docs.python.org/3/tutorial/
• https://github.com/sass/node-sass/issues/1176