C++ Error: 'strcat' was not declared in this scope

This error message indicates that the function 'strcat' is not recognized within your current C++ code. The solution is to include the '' header file, which contains the declaration for 'strcat'.

To fix this error, add the line '#include ' at the top of your C++ file, before any other include statements.

Example:

#include <cstring>
#include <iostream>

int main() {
  // Your code using strcat
  return 0;
}

By including '', you're providing the compiler with the necessary information about the 'strcat' function, allowing your code to compile successfully.