Some things I noticed thatwould improve your program:
Include header file "string" and write your struct more like this:
1 2 3 4 5 6 7
struct customer
{
std::string firstname;
std::string lastname;
int age;
char Gender; // ,<--- just needs to be a single char.
};
Using std::string will allow the first and last names to be any size that is needed. Or I would change the size of the array to 15, 20 or 25. Also I would use std::getline() to input the names because "std::cin >>" will iput to the first white space or a "\n" which ever comes first, so you could loose part of a name.
int nic[5] = { 0,0,0,0,0 }; can easily be written as: int nic[5]{ 0 }; which will initialize the entire array to zeros.
void main() should be written as int main().
After that some of the functions just need to be completed to have a working program.
pseudo code ... some places have a standard for it, others just make it up, but generally you want to get rid of language details like cout << becomes print() or std::blah becomes blah and for loops might be simpler such as for i = 1 to 10 etc.
I find it really hard to write p-code for classes and OOP. There are too many things you have to think about that are too ingrained in the language.
write the Pseudo code first. If you don't then you should damn sure use comments, unlike your example. Using good comments, you can just print the comments and use that for pseudo code.
Make it like a flow chart
program start
Do something
get user input
if y
Do again
if n
program end