# Quick primer

Let's start with a very short and simple function:

![](/files/kompUZi9wZHLueWhz7CC)

We decompile it with **View, Open subviews, Pseudocode** (hotkey **F5**):

![](/files/6nLTArQL9cwnqWNNSXTx)

While the generated C code makes sense, it is not pretty. There are many cast operations cluttering the text. The reason is that the decompiler does not perform the type recovery yet. Apparently, the **a1** argument points to a structure but the decompiler missed it. Let us add some type information to the database and see what happens. For that we will open the **Local Types** window (**Shift-F1**) and add a new structure type:

![](/files/gpoaNrw1l68coXTN5o2E)

After that, we switch back to the pseudocode window and specify the type of **a1**. We can do it by positioning the cursor on any occurrence of **a1** and pressing **Y**:

![](/files/BTlRjxwLraX4XhvQ5GlO)

When we press **Enter**, the decompilation output becomes much better:

![](/files/XMPZY5Z1nKUGBkxjmBpB)

But there is some room for improvement. We could rename the structure fields and specify their types. For example, **field\_6B1** seems to be used as a counter and **field\_6B5** is obviously a function pointer. We can do all this without switching windows now. [Only the initial structure definition required the **Local Types** window](#user-content-fn-1)[^1]. Here is how we specify the type of the function pointer field:

![](/files/UNfklRfBgW07IHs54sE4)

The final result looks like this:

![](/files/Ne3opoktmeinDOKn7fZf)

Please note that there are no cast operations in the text and overall it looks much better than the initial version.

[^1]: This is not completely true. In fact, we could enter the full structure definition in the type dialog box, but it is difficult because the input field consists of a single line. We could also define new types with the **File, Load file, Parse C header file** command.


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