Newbie C Programmer - Confusion over output of a simple program

[omani]

Sir, I wrote a simple program:

#include <stdio.h>


main()
{
    char nam[100];
    char place[50];
    int a;
    printf("\n\tHi, what's your name? ");
    gets(nam);
    printf("\n\tWelcome to our show, %s\n",nam);
    printf("\n\tHow old are you? ");
    scanf("%d",&a);
    printf("\n\tHmm, you don't look a day over 22\n");
    printf("\n\tTell me, %s, where do you live? ",nam);
    gets(place);
    printf("\n\tOh, I've heard %s is a lovely place\n",place);
}

which on execution should gives the following output:

Hi, what's is your name? David
Welcome to our show, David
How old are you? 27
Hmm, you don't look a day over 22
Tell me, David, where do you live? California
Oh, I've heard California is a lovely place

where underlined & italics are typed by the user.

I have not been able to find out anything wrong with my firts code, but on execution it runs fine as expected till 4th line of the output, but in the 5th line where it should ask for the input, prints the last two line as it is without the input (California here).
But when i repeat gets(place) one more time in my code as

printf("\n\tTell me, %s, where do you live? ",nam);
    gets(place);
    gets(place);
    printf("\n\tOh, I've heard %s is a lovely place\n",place);

the program runs exactly as expected.

So sir, please anybody explain me the reason for why my first code did not run as expected and why the second code demands another gets(place) to run as expected.

[Salem]

Well first of all, you shouldn't be using gets() at all.
FAQ > Why gets() is bad / Buffer Overflows - Cprogramming.com

You also need to understand how scanf functions work.
Given a statement of
scanf("%d",&a);
and an input of
27\n

the scanf call will extract 27 from the stream and leave the \n for something else to deal with.

Unfortunately for you, your next input call sees the trailing \n and is immediately happy - the job is done.

You could try flushing the input buffer -> FAQ > Flush the input buffer - Cprogramming.com

Or adopt a consistent way of reading all input, using only fgets()

    char buff[50];  // deliberately chosen to be no larger than your strings
    printf("\n\tHi, what's your name? ");
    fgets(buff,sizeof(buff),stdin);
    sscanf(buff,"%s",nam);
    printf("\n\tWelcome to our show, %s\n",nam);
    printf("\n\tHow old are you? ");
    fgets(buff,sizeof(buff),stdin);
    sscanf(buff,"%d",&a);
    printf("\n\tHmm, you don't look a day over 22\n");
    printf("\n\tTell me, %s, where do you live? ",nam);
    fgets(buff,sizeof(buff),stdin);
    sscanf(buff,"%s",place);
    printf("\n\tOh, I've heard %s is a lovely place\n",place);

Both fgets and sscanf return a success/fail status, which should be checked in any production program.

Whilst it's easy to write a short program when your user is competent and cooperative, most of the time, you need to consider the cooperative but incompetent user.

The real problems come when the (ab)user is both competent and hostile. These users will deliberately try to break your program by feeding it garbage.