Lära Declaring and Initializing Arrays

When you work with arrays in C++, you need to know how to declare them and set their initial values. The basic syntax for declaring an array includes the type of elements it will hold, the array's name, and its size in square brackets. For example, to declare an array of five integers, you write int numbers[5];. You can also initialize arrays in different ways: by leaving them uninitialized, by setting all elements to zero, or by providing explicit values for each element.

main.cpp


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#include <iostream>

int main()
{
    // Uninitialized array
    int uninitialized[5];

    // Zero-initialized array
    int zeroed[5] = {};

    // Explicitly initialized array
    int explicitVals[5] = {1, 2, 3, 4, 5};

    std::cout << "Uninitialized: ";
    for (int i = 0; i < 5; ++i) std::cout << uninitialized[i] << " ";
    std::cout << "\nZero-initialized: ";
    for (int i = 0; i < 5; ++i) std::cout << zeroed[i] << " ";
    std::cout << "\nExplicit values: ";
    for (int i = 0; i < 5; ++i) std::cout << explicitVals[i] << " ";
    std::cout << std::endl;
}

In the code above, you see three different ways to declare and initialize an integer array. The first array, uninitialized, is declared with a size of 5 but without any initial values. This means its contents are undefined and could be anything. The second array, zeroed, is declared with empty braces, which sets all its elements to zero. The third array, explicitVals, is initialized with specific values for each element, so you know exactly what is stored in each position. The output will show you the differences: zeroed will always be all zeros, explicitVals will always match the specified numbers, but uninitialized may display unpredictable values.

main.cpp


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#include <iostream>

int main()
{
    int arr[4]; // uninitialized array

    std::cout << "Contents of uninitialized array: ";
    for (int i = 0; i < 4; ++i)
        std::cout << arr[i] << " ";
    std::cout << std::endl;
}

If you forget to initialize an array, it may contain whatever data was previously in that area of memory, resulting in garbage values. This can cause your program to behave unpredictably, making it hard to find and fix bugs. Always initialize your arrays to avoid these issues.

Note

Uninitialized arrays may contain garbage values, leading to bugs.

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main.cpp


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#include <iostream>

int main()
{
    // Uninitialized array
    int uninitialized[5];

    // Zero-initialized array
    int zeroed[5] = {};

    // Explicitly initialized array
    int explicitVals[5] = {1, 2, 3, 4, 5};

    std::cout << "Uninitialized: ";
    for (int i = 0; i < 5; ++i) std::cout << uninitialized[i] << " ";
    std::cout << "\nZero-initialized: ";
    for (int i = 0; i < 5; ++i) std::cout << zeroed[i] << " ";
    std::cout << "\nExplicit values: ";
    for (int i = 0; i < 5; ++i) std::cout << explicitVals[i] << " ";
    std::cout << std::endl;
}

main.cpp


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#include <iostream>

int main()
{
    int arr[4]; // uninitialized array

    std::cout << "Contents of uninitialized array: ";
    for (int i = 0; i < 4; ++i)
        std::cout << arr[i] << " ";
    std::cout << std::endl;
}

Note

Uninitialized arrays may contain garbage values, leading to bugs.

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 2