Question

I have often seen cases where in a series of printf statements that ask for an input, certain
statements do not accept an input, i.e.

printf_statement1:

printf_statement2: /*Enter input here*/

i.e. before the user enters an input for statement1, statement2 is printed, that allows the user to enter an input, and then repeats the same with statement3 & statement4.

What prompts such a case?

I encounterd this, but not any more, in:

 printf("\n\n\t\tName: ");
 scanf("%s", name); //initially used gets
 printf("\n\n\t\tType: ");     
 scanf("%c", &type);
 printf("\n\n\t\tAddress: ");      //initially used gets
 scanf("%s", address);
 printf("\n\n\t\tDate - of - Birth: ");
 scanf("%s", dob); //initially used gets

Output:

Name:
Type: I enter something!
Address:
Date - of - Birth: I enter something!

Answer 1

Sometimes in cases like these, it is helpful to call fflush() on stdin before reading from it:

char name[40+1];
printf("\n\tName: ");
fflush(stdin);
scanf("%40s", name);

Depending on the circumstances, there may be a newline in the input buffer that causes your first scanf to get skipped (given no input).

Also note that you should specify the size of the buffer in scanf as to avoid buffer overflows.

A format specifier for scanf looks like this:

%[*][width][modifiers]type

width: Specifies the maximum number of characters to be read in the current reading operation

Thus, the %40s specifies that only 40 characters may be read in to the string. Note that the buffer is 41 characters, leaving room for the NULL terminator.

Edit: Some sources (like this and this) say that you should avoid calling fflush(stdin) and it is incorrect. However, the Linux man page states:

For input streams, fflush() discards any buffered data that has been fetched from the underlying file, but has not been consumed by the application.

Conforming to C89, C99, POSIX.1-2001, POSIX.1-2008.
The standards do not specify the behavior for input streams. Most other implementations behave the same as Linux.

Additionally: MSDN says nothing about calling fflush(stdin) other than the following:

If the stream is open for input, fflush clears the contents of the buffer.

One would think that if calling fflush(stdin) was such a problem, one of the two largest sources of documentation on fflush would have mentioned this.