Question

Are programs expressed as English statements. What would each display on the screen if they were actual programs? The variable sum starts with the value 0. Add 10 to sum. Add 15 to sum. Add 20 to sum. Display the value of sum on the screen.

Short answer

Answer: The final output of the given algorithm is 45.

Step-by-step solution

Initialize the variable "sum" at 0

Initialize the variable "sum" by assigning the value 0, like this: sum = 0.

Add 10 to sum

To add 10 to "sum", perform the operation "sum = sum + 10". This means, take the current value of "sum" (which is 0), add 10 to it, and store the result back in the variable "sum". So, sum = 0 + 10 = 10.

Add 15 to sum

To add 15 to "sum", perform the operation "sum = sum + 15". In this case, the current value of "sum" is 10, so sum = 10 + 15 = 25.

Add 20 to sum

To add 20 to "sum", perform the operation "sum = sum + 20". In this case, the current value of "sum" is 25, so sum = 25 + 20 = 45.

Display the value of sum on the screen

Finally, we have computed the value of "sum" as 45. To display this value on the screen, we would use a print statement, like this: print(sum). The output of the program would display "45" on the screen, because that is the value of sum after executing all the addition steps.

Key concepts

Understanding Variables

Variables are like containers that store data values in a program. In programming, we use variables to hold information that our program can manipulate. When you declare a variable, you give it a name and assign it a value. This allows the computer to know what data it should keep track of.

In the original exercise, "sum" is a variable. It starts with a value of 0, which means we initialize it by writing `sum = 0`. The variable name "sum" is a simple way to remember what it stores—in this case, the total sum of several numbers.

Variables can change during the execution of the program. As seen in the steps provided, the value of "sum" updates as we add more numbers to it. Every time we perform an operation, the result is stored back into "sum", making it easy for us to track the computations.

Remember:

• Always give your variables meaningful names.
• Initialize your variables to start them with a known value.
• Keep track of the current value of your variables as your program runs.

Performing Arithmetic Operations

Arithmetic operations are essential in programming whenever you need to perform calculations. They include addition, subtraction, multiplication, and division, among others. These operations manipulate the values of variables and are fundamental to creating useful programs.

In the exercise, arithmetic operations are used to update the value of "sum". The operation `sum = sum + 10` takes the current value of the variable "sum", adds 10 to it, and stores the new result back in "sum". This operation is repeated with different values (15 and 20) to accumulate a final total.

Arithmetic operations follow basic mathematical principles and are performed in sequence from left to right. In more complex situations, you might deal with precedence, where certain operations are performed before others, such as multiplication before addition.

Key points:

• Addition (`+`) increases the value of a variable.
• The result of an arithmetic operation is stored back in the variable for future use.
• Operations should be performed in the logical order they are intended.

Using Output Statements

Output statements in programming are used to display information to the user. They are essential for showing the results of computations or the status of the program.

In many programming languages, output statements are performed using functions or commands like `print` in Python. In the original problem, `print(sum)` is used to display the final value, which is 45, to the screen.

The purpose of output statements is to communicate the program's results or progress to the user. It is important to ensure that the output is clear and provides meaningful information to help the user understand what the program has done.

Tips for effective output:

• Make sure output statements are placed where they are logically needed in the program.
• Use descriptive text along with variable values to make the output more informative, like `print("The final sum is", sum)`.
• Testing the output helps verify that the program is working correctly.