# Simple C, C++, Python program

Start with a C++ program, we can start with a simple C++ program, to print out a text to a file, i.e. example2.cpp

```cpp
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile;
  myfile.open ("example2.txt");
  myfile << "Writing this to a file.\n";
  myfile.close();
  return 0;
}
```

You can choose to compile your program first, or you can compile it on a worker node. You may want to compile on the worker node, in case your program is sensitive to the hardware, e.g. can run with CPU-only, CPU+GPU and/or GPU-only depend on the availability of the worker node.&#x20;

We now compile the `example2` first

```
make example2
```

Then you prepare the Slurm submission script, e.g.

```bash
#!/bin/bash
#
#SBATCH --qos=cu_hpc
#SBATCH --partition=cpu
#SBATCH --job-name=example2
#SBATCH --output=example2_log.txt
#SBATCH --nodes=1
#SBATCH --ntasks=1
#SBATCH --time=00:10:00
#SBATCH --cpus-per-task=1
#SBATCH --mem-per-cpu=1G

module purge

#To handle PATHs
export MYCODEDIR=`pwd`
echo "MYCODEDIR = "$MYCODEDIR
echo "TMPDIR = "$TMPDIR

#To run C++ program
cd $TMPDIR
cp $MYCODEDIR/example2 .
chmod a+x example2
rm -rf example2.txt
./example2
cp -rf example2.txt $MYCODEDIR
```

You should get `example2.txt` as an output from your program, and `example2_log.txt` as the log from the Slurm.

For C and Python program, user can follow the same way:

1. Create and test your program
2. Write the submission script
3. Submit jobs to Slurm clusters, and get the output back to your working directory

However, for Python, a user may need specific packages or specific versions which are not installed centrally. User can also set the virtual environment, install on what are needed. You can see example in [Python with VirtualEnv](/slurm/slurm-examples/slurm-python-with-virtualenv.md).


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