The default gcc version on the system prior to this was gcc-4.7. I need the version 8.2 for C++ compilation.
I have installed gcc-8.2.0 through the following steps:
tar xzf gcc-4.6.2.tar.gz
cd gcc-8.2.0
./contrib/download_prerequisites
cd ..
mkdir objdir
cd objdir
$PWD/../gcc-8.2.0/configure --prefix=$HOME/GCC-8.2.0 --enable-languages=c,c++,fortran,go
make
make install
(The installation was done within the /Downloads directory)
After successful installation, the 'which gcc' or 'gcc --version' shows the gcc-4.7 and not gcc-8.2.
This is the outcome after installation of gcc-8.2
>> gcc --version
gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-18)
Copyright (C) 2010 Free Software Foundation, Inc.
How do I use the version 8.2 in this case? Is there a command that follows this step??
Thanks.

What does return? I suspect 4.4.7 is installed /usr/bin/gcc, 8.2 in /usr/local/bin. Why not install the package gcc-8.2? Why keep around an ancient version?

Did you wish to keep the older version?

If not, you should install the newer version in place of the older version.

Typically you would use "sudo make install" and also the configure line would not specify a --prefix option and would instead use the default location for the compiler, such as /usr/bin/gcc.

Note that Red Hat 4.4 ended LTS last year.

This is the result of the search:

$ whereis gcc
gcc: /usr/bin/gcc /usr/lib/gcc /usr/libexec/gcc /usr/share/man/man1/gcc.1.gz

Also, are you suggesting i remove version 4.7 and install gcc-8.2? I just installed 8.2 but 4.7 is the default still. Uninstalling gcc4.7 will effect other older sofwares. No?

I am using CentOS6. I have now removed the version 4.7 by "yum remove gcc" and also manually removed the gcc directory in usr/bin/ and usr/libexec/. Now i will procede with the installation as before??

tar xzf gcc-4.6.2.tar.gz
cd gcc-8.2.0
./contrib/download_prerequisites
cd ..
mkdir objdir
cd objdir
./configure //$PWD/../gcc-8.2.0/configure --prefix=$HOME/GCC-8.2.0 --enable-languages=c,c++,fortran,go
make -j 4
make install -j 4

is this correct ??

Recommend you remove the --prefix term

I tried that. But now after removing gcc4.7 i am getting "error: no acceptable C compiler found in $PATH"

output:

[biopo5]# $PWD/../gcc-8.2.0/configure --enable-languages=c,c++,fortran,go

checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
checking target system type... x86_64-pc-linux-gnu
checking for a BSD-compatible install... /usr/bin/install -c
checking whether ln works... yes
checking whether ln -s works... yes
checking for a sed that does not truncate output... /bin/sed
checking for gawk... gawk
checking for libatomic support... yes
checking for libitm support... yes
checking for libsanitizer support... yes
checking for libvtv support... yes
checking for libmpx support... yes
checking for libhsail-rt support... yes
checking for gcc... no
checking for cc... no
checking for cl.exe... no
configure: error: in `/home/keretsu/Downloads/buildobj':
configure: error: no acceptable C compiler found in $PATH
See `config.log' for more details.

was it a mistake to remove all gcc directories from /usr/lib and /usr/libexec/gcc ??

Appreciate you help.

That makes sense actually. You removed the compiler, therefore you cannot build a new one, because there's no longer a compiler.

Best that you install using the package manager, as RandomTroll suggested.