COMP1511 Week 04 Tutorial Questions

Your tutor has asked a lab pair to present their week 3 work.

Discuss the good, the bad and the ugly aspects of their code.

Please be gentle in any criticism - we are all learning!

New lab pairs - you will have a new lab partner for weeks 5-8.
Your tutor will facilitate the formation of new pairs.
Please cooperate with them.
Blogging starts this week - what do you have to do?
What is the value of an uninitialized variable?
What sort of problems can be caused by using uninitialised variables in programs?
Why do programs with uninitialised variables apparently work?

Consider the following program square.c

#include <stdio.h>

int main(void) {
    int number;
    int row, column;

    // Obtain input
    printf("Enter size: ");
    scanf("%d", &number);

    row = 1;
    while (row <= number) {
        column = 1;
        while (column <= number) {
            printf("*");
            column = column + 1;
        }
        printf("\n");
        row = row + 1;
    }

    return 0;
}

The output if the user types in the number 5 is:

 ./square
Enter size: 5
*****
*****
*****
*****
*****

Modify the program so that it prints out a triangle like this:

 ./triangle
Enter number: 5
----*
---**
--***
-****
*****

Now modify so it prints the following pattern:

./diagonal
Enter an integer: 10
*---------
-*--------
--*-------
---*------
----*-----
-----*----
------*---
-------*--
--------*-
---------*

Now modify so it prints the following pattern:

./bars
Enter an integer: 9
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-
-*-*-*-*-

Write a C program log10.c which reads a positive integer, and calculates the integer part of its base 10 logarithm without using functions from the maths library.
Hint: repeatedly divide by 10.

Revision questions
The remaining tutorial questions are primarily intended for revision - either this week or later in session.
Your tutor may still choose to cover some of the questions time permitting.
Write a program that reads two integers (height x length) and prints a rectangular, asterisk outline with the specified dimensions, for example:
```
./rectangle
Enter rectangle height and length: 3 5
*****
*   *
*****
```
For the program above consider and discuss the ways in which you would test their correct behaviour. Then extend the program to include error checking for, and handling of, invalid input.

Design and write a program that reads an integer n and prints a diamond asterisk outline with side length n, for example:

./diamond
Enter side length: 3
  *
 * *
*   *
 * *
  *
./diamond
Enter side length: 6
     *
    * *
   *   *
  *     *
 *       *
*         *
 *       *
  *     *
   *   *
    * *
     *

Write a program that repeatedly reads in integers until a non-integer is read in and then prints the number of integers read in. For example:

./readInts
Please enter some integers:
10 -90 100 999 78hello
You entered 5 integers

./readInts
Please enter some integers:
1 2 3 4 5 6 7 8 9
10 11 12 hello
You entered 12 integers

Write a program that reads in an integer n, and then prints a nxn multiplication table. For example:

./multiplication_table
Enter multiplication table size: 5
 1|   1    2    3    4    5
 2|   2    4    6    8   10
 3|   3    6    9   12   15
 4|   4    8   12   16   20
 5|   5   10   15   20   25

Write a program (a small game), which generates a random number for the program-user to guess. For example:

./guess_number
Random number is between 1 and 100.
Enter your guess: 50
Random number is between 1 and 50.
Enter your guess: 40
Random number is between 1 and 40.
Enter your guess: 37

Yay, you guessed the number 37 correctly!


./guess_number
Random number is between 1 and 100.
Enter your guess: 80
Random number is between 80 and 100.
Enter your guess: 90
Random number is between 80 and 90.
Enter your guess: 85
Random number is between 80 and 85.
Enter your guess: 83
Random number is between 80 and 83.
Enter your guess: 82

Yay, you guessed the number 82 correctly!

Revision questions