In C++, when you declare a variable without initializing it, its initial value is undefined, meaning it could contain any value. In your case, when you declare int sum; without initializing it to 0, the sum variable will contain whatever value happens to be in that memory location at the time, which is typically a random or garbage value.
When you then use sum += marc[x]; in your loop, you’re adding marc[x] to this initial garbage value, which leads to unpredictable results.
In contrast, when you initialize sum to 0 (int sum = 0;), you’re ensuring that sum starts with a known value (0), and then you add marc[x] to it in each iteration, leading to the expected result.
In summary, always initialize your variables before using them to avoid unpredictable behavior.
المزيد من المعلومات
When you declare a variable in C++ without initializing it, the variable’s value is considered uninitialized, meaning it can hold any value, including a garbage value left over from whatever was previously stored in that memory location. This behavior is different from some other programming languages where variables are automatically initialized to a default value (such as 0 for integers) if not explicitly initialized by the programmer.
In your case, when you declare int sum; without initializing it, the sum variable will contain whatever value happens to be in the memory location allocated for sum at that time. This value could be anything, depending on the state of the program and the memory allocation strategies of the compiler and operating system.
When you then use the += operator with sum in your loop, you are adding the value of marc[x] to whatever value happens to be in sum at that time. This can lead to unexpected results, as you observed with the “crazy” result of 19557555002.
To avoid such issues, it’s good practice to always initialize your variables when you declare them, especially if you plan to use them immediately in calculations. For example, int sum = 0; initializes sum to 0, ensuring predictable behavior when you later use += with it in your loop.
