The for loop March 9, 2006
1
Count
Count-
-controlled Loops
controlled Loops –
–the for
the for
Loop and Increment Operators
Loop and Increment Operators
Larry Caretto
Computer Science 106
Computing in Engineering
and Science
March 9, 2006
2
Outline
• Review last class
– While and do while loops give test-before
and test-after implementation of loops
– Getting the right count and avoiding off-by-
one errors
• Count controlled loops and the for
statement
• Operators like += and ++ in for loops
• Nested for loops
3
Review Basic Loop Structures
while (
<condition>
)
{// Repeated statements
}
do
{// Repeated statements
}
while (
<condition>
);
4
Review Tracing Loops
count = 0
while (count < 3 ) {
inFile << x << y;
cout << x + y << endl;
count = count + 1
}
• What is printed to screen
for file data as follows:
1 2 3 4 5 6 7 8 9 10 11 12
3
7
11
5
Review Correct Counts
• Watch out for off-by-one errors caused
by bad initial or final count values or by
incorrect condition ( < vs. <= )
• Look at loop counter settings
count = 0; // count = 1;
do {
// calculations and output
count = count + 1
}while ( count < 4 ); // count <= 4
• How many times do we go through loop?
Four times (count = 0, 1, 2, 3) 6
Loop Code Question
• A data file has n sets of data on mass
and velocity
– The first number on the data file is the
number of data sets, n
– This is followed by individual data sets with
mass given before velocity
• Write the looping code that can read n
and the data on mass and velocity data
from the file and print the value of KE =
mV2/2 for each data set
