It’s important to understand the user requirements for ATM machines because you want to make sure your equipment meets the needs of your customers. User requirements can be broken down into two categories: functional and non-functional.
Functional and non-functional requirements, or functional specifications, are not terms specific to ATM machines. You can find these terms used within any business that develops software or systems. User requirements are often accompanied by business requirements and system requirements.
User requirements refer to user needs. For example, what the user actually does with the system (in this case ATM machines) and what activities the user should be able to perform. The customers and their needs inform manufacturer decisions about upgrades and model adjustments.
Now, there are both functional and non-functional user requirements. Functional requirements are mandatory. These are the requirements that users expect each time they visit an ATM machine.
Non-functional requirements are not essential. These requirements are what can make or break the cost of a machine. Non-functional requirements can be left out to save on cost. As long as doing so does not negatively affect the user experience, of course. You might think of functional requirements as needs and non-functional requirements as wants.
For the purpose of this article, we will discuss what functional and non-functional user requirements look like when it comes to your ATM machine. Each has its place, but it’s important that you know what your machine offers your customers.
Functional Requirements for ATM Machines
Functional requirements refer to what the ATM machine should do. This includes ATM behaviors and how the ATM should react when certain conditions are met. For example, the ATM receives input, reacts, and delivers the appropriate output.
The advantage of functional requirements is that they help define service and behavior expectations. If something is missing or if there are errors, it is obvious and can be adjusted. And functional errors are typically relatively cheap to fix.
Functional requirements support user goals, tasks, and activities. Let’s take a look at some examples of functional user requirements for ATM machines.
Examples of Functional User Requirements for ATM Machines
Functional requirements are the mandatory actions the ATM should perform upon user request. We can automatically list those pretty easily: withdraw, deposit, transfer, pay bill, account balance, print receipt, exit. Now let’s look at some of those in terms of input and output. When a user
- inputs the selection to withdraw funds, the ATM should dispense the selected amount
- inputs the selection to receive an account balance, the ATM should display the available amount
- indicates that all transactions have ended, the ATM should return the card and return to its idle state
Above we said that functional requirements refer to how the ATM should behave when certain conditions are met. For instance, when a user inputs the selection to withdraw funds, the ATM should dispense the selected amount from any suitable account linked to the card and upon approval from the bank.
These functional requirements are not unconditional. The ATM can only respond accordingly under the appropriate conditions. Functional requirements include descriptions of
- data entered into the ATM (card, PIN)
- operations performed by each screen (withdraw, deposit, transfer)
- workflows performed by the ATM (transferring funds, accepting envelopes, reporting deposits)
- ATM reports or other outputs (dispensing cash, printing receipt)
- who can enter the data into the system
- how the ATM meets applicable regulatory requirements
When thinking of functional requirements, think of what the customer needs in order to perform his or her transaction. And of course there are many many more user requirements that fall under this category.
But hopefully you get the idea. When the customer does X, the machine does Y. Functional requirements are the observable tasks or processes that must be performed by the ATM machine. So everything else is non-functional.
Non-Functional User Requirements for ATM Machines
The qualities or standards the ATM must have or comply with are non-functional requirements. You might hear them referred to as supplemental requirements or quality of service requirements. They define how the ATM works and describe limits on functionality. So in other words, they specify criteria that judge the operation of the ATM rather than the specific behaviors of the ATM.
While functional requirements answer “what” and “who,” non-functional requirements answer “how” and “to what extent.” And if non-functional requirements are not met, the ATM will still work. Functionality is not dependent upon non-functional requirements.
However, non-functional requirements do help make the ATM easy to use and enhance the ATM performance. They are properties, not features, and focus on user expectations rather than user requirements or needs.
Examples of Non-Functional User Requirements for ATM Machines
Some elements that come to mind when describing non-functional user requirements for ATM machines are accessibility, compliance, performance, security, and usability.
Functional requirements refer to the ATM output itself. And non-functional requirements refer to how quickly the output is received, how easy it is to get the output, and how safely the output is obtained.
So non-functional requirements include safety functions like the key-operated power switch and operator panel. And security protocols like retaining the card after too many unsuccessful PIN attempts. Or performance indicators like speed of transactions.
A Side-by-Side Glance at Functional and Non-Functional Requirements
Again, functional requirements refer to the ATM behavior. Non-functional requirements define the ATM behavior per certain standards. Take a look at the following examples:
| Functional | Non-Functional | |
| PIN | Correct PIN allows transactions | Must be entered correctly within a certain number of attempts |
| Cash Dispenser | Dispenses cash | Can be opened and refilled with cash |
| Printer | Receipt printed upon demand | Can be opened and refilled with paper |
| ATM State | Defaults to idle upon completion of transactions | Can be shut down and restarted |
Functional requirements refer to what the system should do. Non-functional requirements refer to how the system should fulfill those functional requirements. So functional requirements relate to components while non-functional requirements relate to the system as a whole.
The customer doesn’t care how cash is refilled, just that it dispenses cash when prompted. Nor does the customer care how the ATM is powered on and off, just that it’s on when he or she needs to use it. Make sense?
Why it is Important to Understand Functional and Non-Functional Requirements
You can think of these requirements from two perspectives. First, you can think in terms of your customers and users. For example, do the machines you provide offer them the options they both want and need? Are they happy to pay associated fees for these abilities?
Second, you can think of yourself as the customer. What do you need and want from an ATM machine? Does the manufacturer meet those needs for a fair price? If the price is too high, what non-functional or supplemental requirements can you sacrifice to lower the scope or cost of the machine?
And your answers to these questions might be based on your customers’ answers to the same questions. The purpose of functional and non-functional requirements is to make sure customers get a high quality product exactly as they expect it.
Keep this in mind as you shop for ATM machines from different manufacturers. Which model best meets your and your customers’ needs for the best price? Consider non-functional requirements as you weigh your options. ATMDepot.com provides detailed information for each machine listed on the website as well as owner manuals. Take a look and rest assured that you know exactly what you get before you purchase. Still have questions? Contact us today to speak with a representative!