Session-23 CSIT 121 Spring 2006

1
Session-23 CSIT 121 Spring 2006

• Revision Ch 7 Reference Parameters
• Chapter 8 Value Returning Functions
• Demo of writing a value returning function in a
  program

2
Random Number Generation

• You may generate random numbers by calling the
  rand() function in the cstdlib library
• However, it only generates pseudorandom numbers
• Check out the code on the next slide

3
Program Generates Random Numbers

• include ltiostreamgt
• include ltcstdlibgt
• using namespace std
• void main()
• int number
• for (int i0 ilt10 i)
• number rand()
• coutltltnumberltltendl

4
Scaling the Numbers

• The numbers generated are too big
• We may scale them down to a limited range
• How can we make the program generate random
  numbers between 1 and 20?

5
Generating Truly Random Numbers

• In order to generate truly random numbers, use
  the srand function to provide a seed to the
  rand() function
• This seed can also be randomized by using the
  current time as the seed
• Include ltctimegt, and use srand(time(0)) before
  calling the rand() function

6
Lab Demo Due by emailFri Apr 28

• Design the HiLo game with functions. The
  program should call a function to generate and
  return a random number below 100. Players guess
  will be sent to a second function to decide if it
  is too high or too low or just right. Players
  statistics are recorded in a file including the
  guessed number followed by total number of
  attempts. See next two slides

7
Sample Contents of Stats File

• Number Attempts
• 5 7
• 6 8
• 7 1
• 3 2
• Mean 4

8
Bonus Points

• Bonus 50 extra points are awarded for
  introducing a new feature into the program. The
  new feature would allow a player to give up by
  entering a special value (for example 1).
  When the player gives up, that specific number
  and attempts are NOT recorded in the stats file.

9
Practice Problems

• Exam Prep Exercise 15 page 353
• Programming Warm up Exercise 16 page 354
• Programming Warm up Exercise 7 page 413
• Programming Warm up Exercise 14 page 414