Lecture 9:  Iteration

Content Tested:  Writing loops

Lecture Content:

• Iteration
• Loops and Nested Loops
• While statements
• For statements

Goals:

• Ability to synthesize and integrate information
• Learn concepts and theories
• Develop capacity to think for oneself
• Develop ability to think creatively

Assessment Technique:  Programming Activity

Purpose:

Activity:

For each problem, just write the necessary code for the loops.

1.  Write a loop to print out the numbers from 10 to 20, inclusive.  Print the numbers on separate lines.
 
 
 
 
 

2.  Write a loop to print out the numbers 10 to -10, inclusive.  Print the numbers on separate lines.
 
 
 
 
 

3.  Write a loop to add together double type numbers that the user inputs.  The user will enter a negative number to terminate the calculation.  Print out the resulting value.

For example, if the user types 3.2, 5.6, 2.1, 0.1, -1.0 then the printed value should be 3.2 + 5.6 + 2.1 + 0.1 = 11.000.  This is just an example -- remember, the user could type as many positive numbers as he/she would like.
 
 
 
 
 
 
 

4.  Write a nested loop to print out a triangle of size n by n of *'s.  An example 5 x 5 triangle is below.  You may use the variable n without declaring it.

*****
****
***
**
*
 
 

Possible Solution

int i;
for (i = 10; i <= 20; i++){
    printf("%d\n", i);
}

2.

int i;
for (i = 10; i >= -10; i--){
    printf("%d\n", i);
}

3.

double current;
double total = 0.0;

scanf("%lf", &current);
while (current >= 0){
    total = total + current;
    scanf("%lf", &current);
}
printf("Result:  %f\n", total);

4.

int row, col;

for (row = 0; row < n; row++){
    for (col = 0; col < (n - row); col++){
        printf("*");
    }
    printf("\n");
}

Possible Uses of Activity:

• Break students into small groups (2-4 people) and have each group work on the activity.  Encourage one or more groups to present their solution to the rest of the class (If groups write their code on transparency slides, showing the class the code is very easy since it eliminates the time for writing code on the blackboard or on a blank slide on the overhead projector.)  If the instructor sees an error in the program, point it out and ask the rest of the class how one might fix the error and its type (syntax vs. semantic).
• If groups come up with for and while loops, this might be a good time to explain to the class when for loops are appropriate and when while loops are appropriate.