How RPA Works

An RPA bot works by watching how a user interacts with a computer and then repeating those interactions automatically. It identifies the exact buttons, fields, and windows on the screen and controls them just like a human would with a mouse and keyboard.

The Three-Step Engine Behind Every Bot

Every RPA workflow runs on three core operations: Read, Process, Write.

Diagram: The Read–Process–Write Loop

 ┌───────────────┐     ┌───────────────────┐     ┌──────────────────┐
 │    READ       │────▶│    PROCESS        │────▶│    WRITE         │
 │               │     │                   │     │                  │
 │ - Open email  │     │ - Check condition │     │ - Fill form      │
 │ - Open file   │     │ - Apply rules     │     │ - Send email     │
 │ - Scrape web  │     │ - Calculate value │     │ - Save record    │
 │ - Query DB    │     │ - Make a decision │     │ - Update system  │
 └───────────────┘     └───────────────────┘     └──────────────────┘
        ▲                                                 │
        └─────────────── LOOP (repeat for next item) ◀────┘

Step 1 – The Bot Identifies Screen Elements

When a bot runs, it first needs to locate the correct element on the screen — such as a text box, a button, or a dropdown menu. It does this using something called a selector.

A selector is like a home address for a screen element. It describes the exact location and identity of a button or field using properties like its name, ID, position, or the window it appears in.

Real-World Example: Login Form

 Screen Element: Username field in SAP Login Window

 Selector (simplified):
 Window Title = "SAP Logon 750"
 ► Field Label = "User"
 ► Field Type = "Text Input"
 ► Field ID   = "wnd[0]/usr/txtRSYST-BNAME"

 Bot Action: Type "john.doe@company.com" into this field

Step 2 – The Bot Executes Actions

Once the bot locates a screen element, it performs the required action. Common bot actions include:

• Clicking a button
• Typing text into a field
• Selecting a value from a dropdown
• Copying and pasting data
• Opening and closing applications
• Downloading or uploading a file
• Taking a screenshot for logging

Step 3 – The Bot Follows a Workflow

Bots do not perform random actions. They follow a workflow — a structured sequence of steps defined by the developer. A workflow is built using an RPA tool like UiPath or Automation Anywhere using a visual drag-and-drop editor or code.

Diagram: Sample Bot Workflow – Invoice Processing

 START
   │
   ▼
 Open Outlook → Search for emails with subject "Invoice"
   │
   ▼
 Download PDF attachment from each email
   │
   ▼
 Open PDF → Extract: Vendor Name, Invoice No., Amount, Date
   │
   ▼
 Open ERP System (e.g., SAP) → Navigate to "Post Invoice" screen
   │
   ▼
 Fill fields: Vendor Name | Invoice No. | Amount | Date
   │
   ▼
 Click "Post" → Confirm success message appears
   │
   ▼
 Log result in Excel: Invoice No. | Status | Timestamp
   │
   ▼
 Move to next email → Repeat until all emails processed
   │
   ▼
 END → Send summary report by email

How Bots Handle Decisions

Bots can follow rules to make simple decisions. For example: "If the invoice amount is greater than $10,000, send it for manual approval. Otherwise, post it directly."

This type of logic uses standard programming concepts like IF-ELSE conditions. The bot does not guess or think — it checks a rule and picks the right path.

Decision Flow Example

 Invoice Amount Received
         │
         ▼
   Amount > $10,000?
    /           \
  YES            NO
   │              │
   ▼              ▼
 Send for       Post directly
 manual         in ERP
 approval

How Bots Handle Repetition

Most RPA tasks involve processing not just one record, but hundreds or thousands. Bots use loops for this. A loop tells the bot to repeat the same set of steps for each item in a list — such as each row in a spreadsheet or each email in an inbox.

Loop Example

 Excel file has 200 rows of customer data

 Loop starts at Row 1
   → Read customer name, email, account ID
   → Log into CRM
   → Create customer record
   → Save and confirm
 Move to Row 2
   → Repeat
 ...
 Loop ends at Row 200
 → Done. 200 records created.

How Bots Interact with Applications

RPA bots interact with software at the UI (User Interface) layer. This means they work on screen just like a human does — they do not connect through back-end APIs by default. This is why RPA works with almost any application, even old legacy systems that have no modern API.

Interaction Methods

Where the Bot Lives

A bot runs on either a physical machine or a virtual machine (VM). In large companies, many bots run simultaneously on separate virtual machines managed by an Orchestrator — a central control panel that schedules, monitors, and manages all bots.

Summary

RPA bots work by identifying screen elements using selectors, executing a sequence of actions defined in a workflow, and repeating tasks in loops. They make rule-based decisions using IF-ELSE logic. Bots interact with the visible user interface of applications — which means they work on any software a human can operate, without needing back-end code changes.