C-style arrays

Learn to declare C-style arrays with int[] and double[].

C-style arrays

The classic way to declare a fixed-size array in C++ is a C-style array. Its form is int nums[5] = {1, 2, 3, 4, 5};; the size goes inside square brackets and the initial values inside braces.

The size of the array is known at compile time and cannot change later. Indices are zero-based: nums[0] is the first element and nums[4] is the last element of a five-element array. C-style arrays are fast but do not check bounds automatically; that is why std::array is preferred at advanced levels.

Array size

The size of a C-style array is written inside the square brackets and fixed at compile time. int nums[5] reserves space in memory for five int values; this space cannot grow later.

If you write only int nums[5]; without initial values the elements contain garbage. Providing {0} in braces zeroes every element. Giving more values than the size yields a compile error.

Exercise Declare the array and print the first element

Declare a five-element array as int nums[5] = {10, 20, 30, 40, 50}; and print the first element with std::cout << nums[0];. The output must be 10.

Show example solution

#include <iostream>

int main() {
    int nums[5] = {10, 20, 30, 40, 50};
    std::cout << nums[0] << std::endl;
    return 0;
}

Test yourself

For int nums[5] = {1,2,3,4,5}; what is nums[0]?
```
int nums[5] = {1,2,3,4,5};
nums[0]
```
- 0
- 1
- 4
- 5
Show answer

1 — Index 0 gives the first element; the value is 1.

Write the array name

int ____[5] = {1, 2, 3, 4, 5};

Show answer

int nums[5] = {1, 2, 3, 4, 5};

Match each array part to its role

int

Type
nums

Array name
[5]

Size
{1,2,3,4,5}

Initial values

Next lesson: Array access

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