> For the complete documentation index, see [llms.txt](https://mr-poston-1.gitbook.io/c++/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mr-poston-1.gitbook.io/c++/2.-going-beyond-the-basics/2.1-vector-basics/2.1.2-creating-and-accessing-vectors.md).

# 2.1.2 Creating and Accessing Vectors

As mentioned earlier, vectors are a list of values making it easy to store multiple values in a single variable. Vectors are sequential, so you can access values by index and vectors are dynamic and can grow in size.

### Creating Vectors

Vectors are declared using the keyword `vector` followed by the variable type inside of angled brackets.

```
vector<string> strVector;
```

Vectors can be created with or without initial values. To create with initial values, you list the initial values inside curly brackets after the vector name.

```
vector<int> intVector {1, 3, 5, 7, 9};
```

*Note:* In C++, you can optionally use an equals sign ,`=`, between the variable name and the initial value list. In the examples for this course I will not use that equal sign. Either way is considered an acceptable syntax.

While vectors are a part of the standard library, they are not included by default. Anytime you use a vector, you need to import them.

```
#include <vector>
```

### Accessing Values in a Vector

Accessing values in a vector is pretty much the same as accessing individual characters in a string. Like strings, there are two ways to access elements in a vector, using `.at(index)` or with square brackets `[index]`. As with other things, vectors are zero indexed.

Access can be used to get a value as well as update a value.

```
vector<int> intVector {1, 3, 5, 7, 9};

cout << intVector.at(2); // Prints value at index 2: 5

intVector[3] = 11; // Updates value at index 3 to 11
```

While both methods will return value, square brackets provide an undefined behavior when accessing a value out of the range. It may crash your program, or it may return a garbage value.

When attempting to update values, both the `.at()` and `[ ]` will produce an error for an invalid index.

### [Try This Example](https://replit.com/@Poston/212-Creating-and-Accessing-Vectors#main.cpp)