To run the shell:

1. make
2. ./a.out

Exiting From the shell

To exit from the shell, use the command quit

the funcitonalities implemented:

1.cd:

it changes the directory
the commands implemented are:
cd    
cd ..  
cd .   
cd ~   
cd <directory> 
cd - (this changes into the previous working directory)

2.pwd :

     it gives the present working directory

3.echo:

      it prints the message on the terminal

4.ls:

    it lists the contents of the directory
    the commands implemented are:
    ls
    ls .
    ls ..
    ls -l
    ls -a
    ls -al
    ls -la
    ls <directory>
    ls ~

5.background :

            runs a process specified by & in background.

6.foreground:

	runs a process in foreground.

7.pinfo:

prints process info of current shell if no arguments and prints  the process info of process with the argument as pid.

8.environment variables:

setenv :to set the environment variable to a given value
unsetenv:to destroy the variable

9.bg :

changes a stopped background job to a running background job

10.fg :

brings a running or a stopped background job with given job number to foreground

11.jobs :

prints a list of all background processes

12.kjobs :

takes the job id of a running job and sends a signal value to that process

13.overkill :

kills all background processes at once

13.piping with redirection:

one or more commands can be piped.pipe also can be combined with redirection

14.redirection:

output can be redirected to another file and input can be taken from a given file.

15.

CTRL_C:sends SIGINT to the foreground processes of shell
CTRL_Z:send SIGINT and SIGTSTP to foreground process and makes it background process