int currD, currM, currY;
scanf("%d/%d/%d", &currD, &currM, &currY);
I saw this code receiving birth date in the format DD/MM/YYYY, but I wonder what's the meaning of putting '/', I know without this, it will lead to bad input because of the character '/'. So what does it actually mean?
When encountering code that you don’t understand, and which is calling a function from a library, your first order of business is to research the documentation for that function. For C standard functions it’s enough to google the function name.
A good reference in this case is cppreference (don’t be misled by the website name, this is the C reference, not the C++ reference). It gives the function’s definition as
int scanf( const char *format, ... );
Now look for the parameter description of the format parameter:
pointer to a null-terminated character string specifying how to read the input.
The subsequent text explains how to read the format string. In particular:
- […] character [except
%] in the format string consumes exactly one identical character from the input stream, or causes the function to fail if the next character on the stream does not compare equal.- conversion specifications [in] the following format
- introductory % character
- conversion format specifier
d— matches a decimal integer.
In other words:
scanf parses a textual input based on the format string. Inside the format string, / matches a slash in the user input literally. %d matches a decimal integer.
Therefore, scanf("%d/%d/%d", …) will match a string consisting of three integers separated by slashes, and store the number values inside the pointed-to variables.
Is just the separator in the date format. The error must raise when some function searchs for those /.
The first parameter of scanf is a string specifying the format of the string you want to use to store the informations in the further arguments. You can see this format string as a pattern : %d means an integer, and without the '%' it means it just has to match exactly the characters.
Input is expected to provide like 04/07/2019.
If input is provided only 04072019. currD alone hold the value 04072019, currM and currY might garbage value as it is not initialised.
It expects the input to be in the format three integers separated by two slashes ("/"). For example: 10/11/1999.
