1. Revision

2. Generating a pseudo-random number
Necessary libraries: <stdlib.h> and <time.h>
Seeding: srand(time(NULL))
We set the seed based on the current time
NB! Time-dependent seed changes once a second. Don’t use it in a loop!
Tip: use a fixed constant as seed to always test with the same set of “random” numbers
Generating a random number: rand() function
Function returns a random number
The returned value is a positive integer
The number is between 0 … RAND_MAX (the #define comes from stdlib.h library)
2018
Risto Heinsar

3. Sample code to get a pseudo-random number
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(void) {
srand(time(NULL)); // set the seed, we do this ONLY ONCE!
int randNum;
randNum = rand(); // call the random number function, store the return
printf("max is %d\n", RAND_MAX); // largest possible random number (can’t be changed)
printf(“Got: %d\n", randNum); // print out the number that rand() function returned
printf(“Got: %d\n", rand()); // print out another number that rand() function returns
printf(“Got: %d\n", rand() % 10); // numbers from 0 to 9
return 0; }
2018
Risto Heinsar

4. Lab task #1: lottery Lotto numbers should be in between 1 … 30
The user is asked for 6 numbers
Program generates 10 numbers at random
Display the winning numbers
Check and print how many and which of the numbers matched
If all 6 matched, congratulate the user on winning the jackpot
Give your condolence when none of the numbers matched
Advanced: make sure none of the user entered and generated numbers occur twice
2018
Risto Heinsar