Measure user response time using getch() funtion.

response.c

#include <termios.h>
#include <stdio.h>
#include<time.h>
#include<stdlib.h>

static struct termios old, new;

/* Initialize new terminal i/o settings */
void initTermios(int echo)
{
  tcgetattr(0, &old); /* grab old terminal i/o settings */
  new = old; /* make new settings same as old settings */
  new.c_lflag &= ~ICANON; /* disable buffered i/o */
  new.c_lflag &= echo ? ECHO : ~ECHO; /* set echo mode */
  tcsetattr(0, TCSANOW, &new); /* use these new terminal i/o settings now */
}

/* Restore old terminal i/o settings */
void resetTermios(void)
{
  tcsetattr(0, TCSANOW, &old);
}

/* Read 1 character - echo defines echo mode */
char getch_(int echo)
{
  char ch;
  initTermios(echo);
  ch = getchar();
  resetTermios();
  return ch;
}

/* Read 1 character without echo */
char getch(void)
{
  return getch_(0);
}

/* Read 1 character with echo */
char getche(void)
{
  return getch_(1);
}

/* Let's test it out */
int main(void) {

        int i;
        double elapsed[3];
        struct timeval begin, end;

        for(i=0; i<3; i++){

                srand(time(NULL));
                int ranTime = rand()%3+1;
                int ranNum = rand()%10;
                char ranCha = (char)(((int)'0')+ranNum);
                char c;

                printf("\nWait 1 to 3 seconds & enter the diplayed number...\n");
                sleep(ranTime);
                printf("%d\n", ranNum);

                gettimeofday(&begin, NULL);

                while(1){
                        c = getche();
                        if(c==ranCha){
                                printf("\t(Correct)\n");
                                break;
                        }
                        else printf("\t(Try again)\n");
                }

                gettimeofday(&end, NULL);

                elapsed[i] = (end.tv_sec - begin.tv_sec) +
                      ((end.tv_usec - begin.tv_usec)/1000000.0);

                //printf("You spent %f seconds\n", elapsed[i]);

        }

        printf("\n________Summary_______\n");
        double minTime = elapsed[0];
        double maxTime = elapsed[0];
        if(elapsed[1]<minTime) minTime = elapsed[1];
        if(elapsed[2]<minTime) minTime = elapsed[2];
        if(elapsed[1]>maxTime) maxTime = elapsed[1];
        if(elapsed[2]>maxTime) maxTime = elapsed[2];

        printf("Minimum Time: %f\n", minTime);
        printf("Maximum Time: %f\n", maxTime);
        printf("Average Time: %f\n\n", (elapsed[0]+elapsed[1]+elapsed[2])/3);

        return 0;
}