The compilation was successful, why is the answer wrong?

Summary. If it is a cracked version or an official cracked version, there may be some operational failures.

Why do compiler errors occur?

When I was programming C++ in Visual Studio2019, he always had a jumper error, and it couldn't run, so I made it according to the book, and I couldn't find the reason.

If it is a cracked version or an official cracked version, there may be some operational failures.

a=sum;should be put in main.

Move it to printf....the previous line.

a=sum;This is an executable statement, and since it doesn't belong to any function, it will give an error, and you can move it to a pair of curly braces around the main function, such as before the printf statement.

Programming errors are generally classified into the following types:

1) Syntax error in the program source. This type of error is the easiest to detect. For example, a variable is used without being defined in C. The following is an example of a source program:

void main( )

Because the n2 variable is not defined before the printf statement is used, the program will have a syntax error when compiling the source program with the compiler.

2) Warning error in the program source**. This type of error is not as easy to detect as in (1). The usual cases are:

Arrays are out of bounds, or a variable is defined but referenced without initializing it, and so on. These can cause inexplicable errors in the program. These errors make it more difficult to debug the program.

The following is an example of a source program:

Procedure. 1. An example of an array out-of-bounds problem.

void main( )

Procedure. Second, a variable is defined, but it is used as an example without initializing it.

void main( )

The function of the program is to cycle the value of variable i from 0 to 100, find the sum of accumulations, and save the result in the variable sum. Since the variable sum is not zeroed out before entering the for loop (sum = 0), the program will run randomly depending on the C compiler and the computer operating system (Windows or Linux).

Procedure. Errors in the first and second programs are warning errors. The C compiler does not check for out-of-bounds arrays in the program when compiling such programs, or for references that define a variable but are not initialized. This kind of error is more difficult for users to debug.

As for how long it takes to be able to debug all the source programs you have written, this varies from person to person. People with rich programming experience will spend less time. Conversely, it will take longer to debug the program.

Actually, your problem can be summarized as how to check for bugs:

1. Troubleshooting process.

The process of solving bugs can be painful, tiring, uncomfortable, stressful, or even temporarily unsolvable, depending on whether you are doing your best. If you want to improve yourself and reach a higher level, you must cross this hurdle, otherwise you can only be a mediocre programmer who can only take on some simple tasks.

The process of solving bugs can also learn a lot of things, but also a lot of fun, you can also get a lot of improvement, solving bugs is within the scope of your own responsibility, is a kind of fun or a burden, the key depends on the personal mentality.

Finally, I would like to share with you a very famous saying called "the peak is high and there is no smooth road", which means: if you want to climb the highest peak to enjoy the beautiful scenery, there is no smooth road to walk, there are cliffs, and if you want to climb the peak to enjoy the beautiful scenery, you must cross these hurdles.