Setting Permissions to a file in C to Read Only

I'm new to C programming and I'm trying to experiment with setting the permissions of a file to Read Only. I'm sure that I don't have the directives correct and when I try to compile I get the error on the line that #include <io.h> is on "fatal error: io.h no such file or directory". The file 'time.log' is in a directory called 'time_logs' and the program will run from the same directory that the directory 'time_logs' is in.

OS is Rasbian for Raspberry Pi 4 Arm Using GCC

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <io.h>
#include <sys.h>


struct stat st = {0};

int main(void){


      if(_chmod("time_logs/time.log", _S_IREAD) == -1)
         perror("Not found");

        else{
              _chmod("time_logs/time.log", _S_IREAD);

             }
}