gcc software package provides GNU C compiler, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gcc
gcc is installed in your system.
Make ensure the gcc package were installed using the commands given below,
$ sudo dpkg-query -l | grep gcc *
You will get with gcc package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Development |
| Package | gcc |
| Version | 4:6.1.1-1 |
| Description | GNU C compiler |
| Sub Section | devel |