General Structure
=================

In Qbics, all computational settings are given in a single input file. The following one is a basic Qbics input file:

.. code-block:: bash
    :linenos:
 
    # A CHARMM calculation.

    charmm
      parameters par_all35_ethers.prm # Parameter files. There can be several ones.
      topology   ether.psf            # Topology file.
    end

    mol
        O   0.00000000000000      0.05011194954430      0.05011194954224
        H   0.00000000000000     -0.06080277603381      1.01069082652926
        H   0.00000000000000      1.01069082648951     -0.06080277607149
    end

    task
      energy charmm
      opt charmm
    end

- You can insert comments at any place using ``#``.
- Statements like ``mol ... end`` are called an option block. In this example, we have ``charmm`` and ``mol`` blocks. They give details about how calculations should be done by Qbics.
- A special block is ``task``. It tells Qbics what tasks to do. In this example, there are two calculations: ``energy charmm`` and ``opt charmm``. They will be done one-by-one.