Member Avatar for karthisargunan

Hello,
I am developing the project of "Employee Information System" using C language, In this project i want to add the mobile number for the each employee {Each Mobile number having 7 characters, Bcoz if we using the integer means, Any of one employee has no mobile number it’s not print the "0000000" format of mobile number} So if it okay means You will send the clear details about, "How to add the mobile number and also How to increase that to each employee "ASAP.
Contact Mail ID : [removed]

Thanks & Regards,
B.Karthikeyan

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Generated

Summary of safe, practical options (building on suggestions from , , and ):

Store the 7-digit mobile as text so leading zeros survive (use an 8-byte buffer: seven digits + terminating NUL). To auto-assign the next number, either convert->increment->format (watch for overflow and bad input) or implement a simple digit-by-digit carry. The latter is small, fast, and avoids integer overflow or locale issues — it is what suggested in words and is implemented below.

/* Increment a 7-digit phone string in-place.
   phone must be an 8-byte buffer (7 chars + '\0').
   returns 0 on success, 1 if overflow ("9999999"), -1 on invalid input.
*/
int inc_phone7(char phone[8]) {
    for (int i = 6; i >= 0; --i) {
        if (phone[i] < '0' || phone[i] > '9') return -1;
        if (phone[i] != '9') { phone[i]++; return 0; }
        phone[i] = '0';
    }
    return 1;
}

Example usage pattern: keep the last-assigned number persistent (file or DB). When adding an employee, copy the last number into the new record, call inc_phone7() and save it back as the new last-assigned value. Keep the phone field as char phone[8] inside your struct Employee.

Troubleshooting and best practices:

  • Validate input digits with isdigit() before incrementing.
  • Decide policy for overflow ("9999999"): error, wrap, or expand format.
  • Don’t use "0000000" as the only indicator of “no phone” — use an extra flag (e.g., has_phone) or an empty string to avoid clash with a real number.
  • For multi-process/multi-user programs, persist the last-assigned value and use a lock or transactional DB update to avoid races.
  • If you prefer numeric conversion, use strtoull + snprintf with error checks (safer than atol), but remember to validate and handle overflow.

This keeps numbers fixed-width, preserves leading zeros, and gives predictable behavior when auto-incrementing.

Recommended Answers

All 11 Replies

Member Avatar for ithelp

Use char string[10] .

Member Avatar for karthisargunan

Use char string[10] .

thanks fore ur reply.
But i need the number are automatically incrementing that is If u enter Mobile no :1234567 for employee 1 na 2nd employee will directly get the next no that is 1234568
Reply me ASAP.

Regards,
B.Karthikeyan

Member Avatar for Murtan

It seems as if you have a solution in mind, why don't you try to implement it and if you have any trouble, post your code along with the question. (Something like "I expected it to do ___ but it is doing ___")

Oh, and when posting c code, please use c code tags
[code=c] /* Your code here */

[/code]

Member Avatar for ajay.krish123

You can enter the first mobile number

scanf("%d",&mobileno[0];

rest all the numbers will be as

for(i=0;i<n;i++)
mobileno[i+1]=mobile[i]+1;
Member Avatar for karthisargunan

It seems as if you have a solution in mind, why don't you try to implement it and if you have any trouble, post your code along with the question. (Something like "I expected it to do ___ but it is doing ___")

Oh, and when posting c code, please use c code tags
[code=c] /* Your code here */

[/code]

HI,

I store employee's 7digit phone number as string. I want to allocate numbers to them For each employee the phone number should be 1 value greater than previous employee.
So, I need to increment ph number by 1.
How to increment a string?
Regards,
Karthikeyan.B

Member Avatar for Murtan

Please don't answer each post since your last with the same string, we all have to read through all of them.

I can't imagine any phone system where you can pre-order sequential 7 digit phone numbers, but ignoring that for now...

Why does the 7 digit phone number have to be a string?

Or if it does, why can't you convert it from a string to a number, add one and convert it back?

If you're REALLY desperate, you could convert the last character of the phone number to a number and add 1. If the number is now 10, put a '0' down for the last digit and 'carry' the one to the next-to-the last character. (At least that's how I learned to do manual addition when I was in school.)

commented: Very good, nice simple "string" addition, just like how it's done on paper. +27
Member Avatar for karthisargunan

Please don't answer each post since your last with the same string, we all have to read through all of them.

I can't imagine any phone system where you can pre-order sequential 7 digit phone numbers, but ignoring that for now...

Why does the 7 digit phone number have to be a string?

Or if it does, why can't you convert it from a string to a number, add one and convert it back?

If you're REALLY desperate, you could convert the last character of the phone number to a number and add 1. If the number is now 10, put a '0' down for the last digit and 'carry' the one to the next-to-the last character. (At least that's how I learned to do manual addition when I was in school.)

Hi,
Bcoz,1 employee is not having a mobile no means, output for that employee is 0000000 by using string,But if i am using integer means its not possible.That y i asked you.
Regards,
Karthikeyan.B

Member Avatar for Murtan

What about the rest of the post?

Why can't you convert from a string to a number, add one and convert it back?

And if an employee didn't have a mobile, I'd leave the field blank, not fill it with zeros.

Member Avatar for ajay.krish123

What code have you tried until now??

Member Avatar for Salem

It's quite simple, you take
char phone[] = "0000000";

Then write a function to do addition like you would on paper.
char phone[] = "0000001";

When you get to
char phone[] = "0000009";
the next one will be
char phone[] = "0000010";

Member Avatar for Ancient Dragon

Or just convert to int, add one, then convert back to string, as previously suggested

char phone[] = "0000000";
int ph = atol(phone)+1;
sprintf(phone,"%08d", ph);
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