5.5. Two-dimensional tables¶
A two-dimensional table is a table where you choose a row and a column and read the value at the intersection. A multiplication table is a good example. Let’s say you wanted to print a multiplication table for the values from 1 to 6.
A good way to start is to write a simple loop that prints the multiples of 2, all on one line.
Run the active code below, which uses a simple loop that prints the multiples of 2, all on one line.
The first line initializes a variable named i, which is going to act
as a counter, or loop variable. As the loop executes, the value of
i increases from 1 to 6, and then when i is 7, the loop
terminates. Each time through the loop, we print the value 2*i
followed by three spaces. By omitting the newline from the first output
statement, we get all the output on a single line.
The output of this program is:
2 4 6 8 10 12
So far, so good. The next step is to encapsulate and generalize.
- counter
- Try again!
- loop variable
- Try again!
- Both a and b
- Correct!
- None of the above
- Try again!
Q-2: What is a good name for the variable x, found in the code block below?
#include <iostream>
int main() {
int x = 1;
while (x <= 6) {
std::cout << 2*x << " ";
x = x + 1;
}
cout << endl;
return 0;
}
- Change the first output statement to say cout << 3*x << endl;
- The addition of the endl will print the multiples of three on separate lines.
- Change the first output statement to say cout << 3*x << \n;
- A newline character must be used in conjunction with a string. In this case, we are outputting an integer. To use a newline character in this scenario you must use quotes around it. (ex. "\n")
- Change the second output statement to say cout << endl << endl;
- This would simply print out two new lines after all of the multiples have already printed on one line.
- This code already prints each multiple on its own line.
- This code prints all multiples out on one line.
Q-3: Currently, the code below prints all of the multiples of three on one line. How can you change the output so that each multiple prints on its own line?
#include <iostream>
using std::cout;
using std::endl;
int main() {
int x = 1;
while (x <= 6) {
cout << 3*x << " ";
x = x + 1;
}
cout << endl;
return 0;
}