What is the meaning of a "Secure Code" ?

Question

How can you make a code "safer" from hackers? Or whatever..

Answer 1

I am not really sure what you are asking for (like you), but there is a term "secure coding". It is practice of software developing to write a code that prevents bugs (including those that can be made by outer source such as input) and not giving the user information they should not know. Examples: to prevent buffer overflows (for example, when taking input (especially string); it is actual in languages such as C: using fgets instead of gets for string input; using strtonum, strtol and strtoul instead of atoi, atol, atoul to convert string containing number to number); to prevent ambiguous format of a string (also actual in C); to prevent integer overflow (when the number is greater than maximum number that can be hold in memory and the software can process); to prevent cases when user tries to get server's private information (such as configuration files).
Original information: https://en.wikipedia.org/wiki/Secure_coding

[re-answered: deleted original answer and wrote new, more informative]