# FAQ: Functions - Built-in Functions

This community-built FAQ covers the “Built-in Functions” exercise from the lesson “Functions”.

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This exercise can be found in the following Codecademy content:

## FAQs on the exercise Built-in Functions

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I tried to copy the code into my own compiler on my computer but I get an error:
In function ‘int main()’:
random.cpp:6:10: error: ‘time’ was not declared in this scope
srand (time(NULL));
^~~~
random.cpp:6:10: note: suggested alternative: ‘tm’
srand (time(NULL));
^~~~
tm

Anybody who can explain what went wrong?

Make sure you add `#include <iostream>` at the beginning.

``````#include <iostream>

int main() {
// This seeds the random number generator:
srand (time(NULL));
// Use rand() below to initialize the_amazing_random_number
int the_amazing_random_number = rand() % 29;
std::cout << the_amazing_random_number;
}
``````

#include
int main() {
// This seeds the random number generator:
srand (time(NULL));
// Use rand() below to initialize the_amazing_random_number
int the_amazing_random_number = rand() % 100;
std::cout << the_amazing_random_number << “\n”;
}

Why can the above code not include the following

std::int the_amazing_random_number = rand()%100