Default value for empty entry with scanf() in C

user_10764332 0
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I was looking at the below C code from a study site and wanted to confirm if the default value for an empty entry with scanf("%d", number ) is -1? . That is if 'number' is an 'empty entry' does it automatically get interpreted as -1?

How does the below code not run the first if statement (increment counter) in the 'do" section if the empty entry is not understood as a -1?

int main(void)
{
    int number;
    int max = -100000;
    int counter = 0;

    do {
        scanf("%d",&number);
        if(number != -1)
            counter++;
            if(number > max)
                max = number;
    }
    while (number != -1);
        if(counter)
          printf("The largest number is %d \n",max);
        else
            printf("Hey, you haven't entered any number!");
    return 0;
}
scanf c
1 Answers

There is no such thing as a "default value" for scanf. If scanf fails, no assignment will be made to the pointed to object.

So the idea of the code is that the loop shall continue until the the user inputs a -1.

The code lacks a check of the return value from scanf, i.e. instead of just

scanf("%d",&number);

the code should be like

if (scanf("%d",&number) != 1)
{
     // Invalid input
     // Add error handling or just exit
     exit(1);
}
user_43864270
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