What software do restaurants use for reservations?

Restaurants use a reservation module tied to the floor plan, not a plain calendar. The practical difference: a calendar tells you that 25 people are coming at 20:00, while the floor plan tells you that you have no free table for 6 at that time.

Short answer

Restaurants use a reservation module with a floor plan, which ties a booking to a specific table, not just to a number of seats.
The software keeps bookings in a single list that you see from the same application.
It shows the time slots of each table, so you can see when it frees up.
It keeps group bookings and events on the same floor plan.
Contact details in a booking are personal data, which you use only for the reservation.

What the software must do

Show the floor plan, with the free and the reserved tables for each time slot.
Let you choose a table of the right size, so you do not block a six-top for two guests.
Show bookings by day and by time slot, so you can plan the service.
Keep group bookings on the same floor plan, with party size and time.
Show the cancellation policy before confirmation, if you have one.
Live in the same application as the menu and the orders — otherwise the host works in two places.

What the law says

The name, phone number and email in a booking are personal data and are kept only for as long as you need them (EU Reg. 2016/679).
A reminder for an existing booking is not marketing; promotional messages need separate consent.
The cancellation policy must be stated before the booking is confirmed (OG 21/1992).

Practical example

Hypothetical example: on a Friday night, a 60-seat restaurant has 25 bookings, and some guests do not show up. Every empty table is seats you can no longer sell. Work out the loss with your own figures: the number of empty tables, multiplied by your average check.

A calendar or a paper book does not show which tables are free before the rush. A floor plan shows at a glance which tables are still available.

Common mistakes

Using a generic calendar that knows nothing about tables and their size.
Keeping phone bookings in a notebook and online ones somewhere else — the two never line up.
Not stating the cancellation policy before confirming, which can become a legal risk (OG 21/1992).
Not writing down the bookings that were not kept, so you repeat the same mistake with the same guests.

How 4restaurants.net helps

The floor plan and the bookings sit in the same application as the evening's orders.
The time slots on each table show when the table frees up.
Group bookings and events sit on the same floor plan, with no separate notebook.