ATOI Usage

Question

#include <stdio.h>
int main()
{
char input[10];
int num;

printf("Enter a number: ");
gets(input);
num = atoi(input);

return 0;
}

When i write that program,compiler says that "atoi is not function".But in C course it shows excatly like i wrote...
And one more thing i want to ask,What does atoi exactly do?

Answer 1

I'm very grateful about your answer.Thank you so much!