# What are Signals? — Angular

Source: https://www.geekswithgeeks.com/en/angular/ng-signals-intro

> A reactive primitive that tracks its own readers.

## Why Angular added signals

A **signal** is a wrapper around a value that notifies interested code whenever it changes. Angular uses this to know exactly what to update, instead of checking the whole component tree.

## Like a spreadsheet cell

Think of a signal as a spreadsheet cell: change it, and every formula cell that reads it recalculates automatically — no manual refresh.

## signal()

`signal(initialValue)` creates one. Call it like a function to read it; call `.set()` or `.update()` to change it.

```typescript
import { signal } from '@angular/core';

export class CounterComponent {
  count = signal(0);

  increment() {
    this.count.update(c => c + 1);
  }
}
```

**Quiz:** How do you read the current value of a signal named `count`?

- [ ] count.value
- [x] count()
- [ ] count.get()

*Answer:* count(). Signals are callable — `count()` reads the current value and registers a dependency.