COMP 1917
Computing 1
Session 2, 2016

Tutorial - Week 3

Tutorial Presentation

Given a point P=(x,y) and a triangle ABC with A=(x1,y1), B=(x2,y2) and C=(x3,y3), how can you test whether the point P is inside or outside the triangle? Find out one or two methods for doing this and explain them to the class. (Note: you should explain them using mathematical formulas, not actual C code.)

Week 3 Tutorial Questions

  1. Write a program that given three numbers first, second and third, finds out if the numbers are in strictly descending order (first > second > third). Is there an alternative way to write this program? 
     1 #include <stdio.h>
 2
 3 int main(int argc, char* argv[]){
 4    int first, second, third;
 5    printf("Enter numbers: ");
 6    scanf("%d %d %d", &first, &second, &third);
 7
 8    return 0;
 9 }
  2. Modify previous program to check if three numbers are in ascending or descending order.
  3. Write a program that allows the user to enter at integer and then prints out that many stars, each on a new line. 
    % ./stars
Enter : 5
*
*
*
*
*
  4. Consider the following code: 
     1 #include <stdio.h>
 2
 3 int main( void )
 4 {
 5    int num;
 6    int row, col;
 7
 8    // Obtain input
 9    printf("Enter number: ");
10    scanf("%d", &num);

11    for(col = 1; col <= num; col++){
12       printf("*");
13    }
14    printf("\n");
15
16    for(row = 2; row < num; row++) {
17        for(col = 1; col <= num; col++) {
18            if(col == 1 || col == num){
19                printf("*");
20            }else{
21                printf(" ");
22            }
23        }
24        printf("\n"); // Start a new line
25    }
26
27    for(col = 1; col <= num; col++){
28       printf("*");
29    }
30      printf("\n");
31
32    return 0;
33 }
    What is the output if the user types in the number 4?

    Modify the program so that it prints a triangle instead of a square: 

    $ ./triangle
Enter n ? 6
*
**
***
****
*****
******
    How would you change your program to print the triangle in different orientations? 
    (a) ******   (b)  ******    (c)     *
    *****          *****           **
    ****            ****          ***
    ***              ***         ****
    **                **        *****
    *                  *       ******
  5. Write a program that generates two random numbers between 1 and 107 and check if a smaller number is a factor of a larger.

Presentation Topic for Week 4

Describe the ASCII coding system. (What does ASCII stand for?) Draw a schematic "map" of the ASCII Table on the board, showing (in both decimal and hexadecimal notation) where the following sets of characters lie: