ch02-IPO-Input-Process-Output-Input-Process-Output

Starting out with Programming Logic and
Design
Sixth Edition
Chapter 2
Input, Processing, and
Output
Copyright © 2022, 2016, 2013, 2010 Pearson Education, Inc. All Rights Reserved

Learning Objectives
2.1 Designing a Program
2.2 Output, Input, and Variables
2.3 Variable Assignment and Calculations
2.4 Variable Declarations and Data Types
2.5 Named Constants
2.6 Hand Tracing a Program
2.7 Documenting a Program
2.8 Designing Your First Program
2.9 Focus on Languages: Java, Python, and C++

2.1 Designing a Program (1 of 7)
1. The first step in programming is designing – flowcharts
and pseudocode help with this process.
2. Next, the code is written.
3. All code must be cleared of all syntax errors.
4. After the executable is created, it can be checked for
logic errors.
5. If logic errors exist, the program must be debugged.

The purpose of Programming Logic and Design is to focus
on Flowcharts and Pseudocode.
The design is the foundation of a good program.
The program development cycle

Two steps in designing a program
1. Understand the tasks that the program is to perform.
– Learning what the customer wants.
2. Determine the steps that must be taken to perform the
task.
– Create an algorithm, or step-by-step directions to
solve the problem.
– Use flowcharts and/or pseudocode to solve.

Pseudocode
• Fake code used as a model for programs
• No syntax rules
• Well written pseudocode can be easily translated to
actual code
Display "Enter the number of hours"
Input hours
Display "Enter the hourly pay rate"
Input payRate
Set grossPay = hours * payRate
Display "The gross pay is $", grossPay

Flowcharts
• A diagram that graphically
depicts the steps that take
place in a program
Figure 2-2 Flowchart for the pay
calculating program

• Flowchart Connector Symbol
– Use connectors to break
a flowchart into two or
more smaller flowcharts
and placing them side-
by-side on the page.

• Off-Page Connector Symbol
– To connect flowcharts on different pages

2.2 Output, Input, and Variables (1 of 6)
Output – data that is generated and displayed
Input – data that a program receives
Variables – storage locations in memory for data
Computer programs typically follow 3 steps
1. Input is received
2. Some process is performed on the input
3. Output is produced

Input, Processing, and Output of a Pay Calculating
program:

IPO Chart: Describes the input, processing, and output of a
program.
Example:
IPO Chart for the Pay Calculating Program
Input Processing Output
Number of
hours
worked
Hourly pay rate
Multiply the number of hours
worked by the hourly pay rate.
The result is the gross pay.
Gross pay

Display is the keyword to show output to the screen
Sequence – lines execute in the order they appear
String Literals – a sequence of characters
Figure 2-7 The statements
execute in order
Figure 2-8 Output of
Program 2-1

Input is the keyword to take values from the user of the
program
It is usually stored in variables

Programmers can define variable names following certain
rules
– Must be one word, no spaces
– Generally, punctuation characters are avoided
– Generally, the first character cannot be a number
– Name a variable something that indicates what may
be stored in it
camelCase is popular naming convention

2.3 Variable Assignment & Calculations (1 of 2)
Variable assignment does not always have to come from
user input, it can also be set through an assignment
statement
Set price = 20

2.3 Variable Assignment & Calculations (2 of 2)
Calculations are performed using math operators
The expression is normally stored in variables
Set sale = price – discount
Table 2-1 Common math operators
Symbol Operator Description
+ Addition Adds two numbers
− Subtraction Subtracts one number from another
Asterisk Multiplication Multiplies one number by another
/ Division Divides one number by another and gives the quotient
MOD Modulus Divides one number by another and gives the remainder
Caret Exponent Raises a number to a power
∗
∧

2.4 Variable Declarations & Data Types (1 of 2)
A variable declaration includes a variable’s name and a
variable’s data type
Data Type – defines the type of data you intend to store in
a variable
– Integer – stores only whole numbers
– Real – stores whole or decimal numbers
– String – any series of characters
• Declare Real grossPay

2.4 Variable Declarations & Data Types (2 of 2)
For safety and to avoid logic errors, variables should be
initialized to 0 or some other value

2.5 Named Constants
A named constant is a name that represents a value that
cannot be changed
– Makes programs more self explanatory
– If a change to the value occurs, it only has to be
modified in one place
Constant Real INTEREST_RATE = 0.069

2.6 Hand Tracing a Program
Hand tracing is a simple debugging process for locating
hard to find errors in a program
Involves creating a chart with a column for each variable,
and a row for each line of code
Figure 2-18 Program with the hand trace chart completed

2.7 Documenting a Program
External documentation describes aspects of the
program for the user, sometimes written by a technical
writer
Internal documentation explains how parts of the program
works for the programmer, also known as comments
// Comments are short notes placed in a program.
// They explain how different parts of the
// program work.

2.8 Designing Your First Program (1 of 5)
Calculate the batting average for any player
= ÷
Batting Average Hits Times at Bat
Determine what is required for each phase of the program:
1. What must be read as input?
2. What will be done with the input?
3. What will be the output?

1. Input is received.
– The number of hits
– The number of times at bat
2. Some process is performed on the input.
– Calculate the batting average
– Divide the number of hits by the number of times at
bat
3. Output is produced.
– The player’s batting average

Figure 2-20 Flowchart
for program 2-15

• Summary
– Input
▪ Determine data needed for input
▪ Choose variables to store the input
– Process
▪ Determine calculations to be performed
▪ Choose variables to store the calculations
– Output
▪ Determine what output the program will display
▪ Usually the results of the program’s calculations

2.9 Focus on Languages: Java

2.9 Focus on Languages: Java (1 of 11)
• Setting up a Java Program
public class Simple
{
public static void main(String[] args)
{
}
}
Class Name
Class Header
main Method

• Displaying Screen Output
– System.out.println()
Displays a line of output, then advances the output cursor to the next line.
public class Output
{
{
System.out.println("My major is Computer Science.");
System.out.println("I plan to be a software developer.");
System.out.println("Programming is fun!");
}
}
Program Output
My major is Computer Science.
I plan to be a software developer.
Programming is fun!

– System.out.print()
Displays output, but does not advance the output cursor to the next line.
public class Output2
{
{
System.out.print("Programming");
System.out.print("is");
System.out.print("fun!");
}
}
Program Output
Programmingisfun!

• Variable Declarations (see the rules for variable names on page 76 of your book)
int speed;
double distance;
String name;
Data Type What It Can Hold
byte Integers in the range of –128 to +127
short Integers in the range of –32,768 to +32,767
int Integers in the range of –2,147,483,648 to +2,147,483,647
long Integers in the range of –9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
float Floating-point numbers in the range of ±3.4×10–38 to ±3.4×1038 , with 7 digits of accuracy
double
Floating-point numbers in the range of ±1.7×10–308 to ±1.7×10308, with 15 digits of
accuracy
String Strings of text.

int speed;
double distance;
String name;
byte Integers in the range of -128 to +128
short Integers in the range of -32,768 to +32,767
int Integers in the range of -2,147,483,648 to +2,147,483,647
long Integers in the range of –9,223,372,036,854,775,808 to
+9,223,372,036,854,775,807
float Floating-point numbers in the range of ±3.4 * 10-38 to ±3.4 * 1038, with 7 digits of
accuracy
double Floating-point numbers in the range of ±1.7 * 10-308 to ±1.7 * 10308, with 15 digits of
accuracy
String Strings of text

• Reading Keyboard Input (reading an integer)
import java.util.Scanner;
public class GetAge
{
{
Scanner keyboard = new Scanner(System.in);
int age;
System.out.println("What is your age?");
age = keyboard.nextInt();
System.out.println("Here is the value that you entered:");
System.out.println(age);
}
}
Program Output
What is your age?
24 [Enter]
Here is the value that you entered:
24
Create a Scanner object
Read an integer

• Reading Keyboard Input (reading a real number)
public class GetAge
{
{
double temp;
System.out.println("What is the temperature?");
temp = keyboard.nextDouble();
System.out.println(temp);
}
}
Program Output
What is the temperature?
74.5 [Enter]
74.5
Read a double

• Reading Keyboard Input (reading a string)
public class GetAge
{
{
String name;
System.out.println("What is your name?");
name = keyboard.nextLine();
System.out.println(name);
}
}
Program Output
What is your name?
Jimmy [Enter]
Jimmy
Read a String

• Displaying Multiple Items with the + Operator
Example:
System.out.println("This is " + "one string.");
This statement will display:
This is one string.
Example:
number = 5;
System.out.println("The value is " + number);
This code will display:
The value is 5

• Performing Calculations – Operators
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
Examples:
total = price + tax;
sale = price - discount;
population = population * 2;
half = number / 2;
leftOver = 17 % 3;

• Named constants – use the final key word in declarations:
final double INTEREST_RATE = 0.069;
This declares a double constant named INTEREST_RATE, set to the value 0.069.

• Documenting a program with comments
// This is a line comment
/*
This is a multiline comment.
*/

2.9 Focus on Languages: Python

2.9 Focus on Languages: Python (1 of 8)
– print() function
Displays a line of output, then advances the output cursor to the next line.
print('My major is Computer Science.');
print('I plan to be a software developer.');
print('Programming is fun!');
Program Output
My major is Computer Science.
I plan to be a software developer.
Programming is fun!

• You do not declare variables in Python.
• Instead, you use an assignment statement to create a variable.
• See the rules for variable names on page 81 of your book.
age = 25
title = 'Vice President'

• Pass multiple arguments to the print function, and Python will print each argument's
value on the screen, separated by a space.
age = 25
print('I am', age, 'years old.');
Program Output
I am 25 years old.

• Reading Keyboard Input (reading a string)
first_name = input('Enter your first name: ')
last_name = input('Enter your last name: ')
print('Hello', first_name, last_name)
Program Output
Enter your first name: Vinny [Enter]
Enter your last name: Brown [Enter]
Hello Vinny Brown

hours = int(input('How many hours did you work? '))
print('Here is the value that you entered:', hours)
Program Output
How many hours did you work? 40 [Enter]
Here is the value that you entered: 40

• Reading Keyboard Input (reading a real number)
pay_rate = float(input('What is your hourly pay rate? '))
print('Here is the value that you entered:', pay_rate)
Program Output
What is your hourly pay rate? 20 [Enter]
Here is the value that you entered: 20

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
** Exponent
Examples:
total = price + tax
sale = price - discount
population = population * 2
half = number / 2
leftOver = 17 % 3
result = 4**2

# This is a comment

2.9 Focus on Languages: C++

2.9 Focus on Languages: C++ (1 of 11)
• The typical C++ program contains the following code:
#include <iostream>
using namespace std;
int main()
{
return 0;
}
You will write statements that appear in this area.

• Displaying Screen Output with the cout Statement
– Begins with the word cout
– followed by the << operator
– followed by an item of data that is to be displayed.
– The statement ends with a semicolon.
#include <iostream>
int main()
{
cout << "Hello world";
return 0;
}
Program Output
Hello world

#include <iostream>
int main()
{
cout << "Hello world";
return 0;
}
Program Output
Hello world
#include <iostream>
int main()
{
cout << "Hello " << "world";
return 0;
}
Program Output
Hello world
#include <iostream>
int main()
{
cout << "Hello ";
cout << "world";
return 0;
}
Program Output
Hello world
#include <iostream>
int main()
{
cout << "Hello" << endl;
cout << "world" << endl;
return 0;
}
Program Output
Hello
world

int speed;
double distance;
string name;
short Integers in the range of -32,768 to +32,767
int Integers in the range of -2,147,483,648 to +2,147,483,647
long Integers in the range of -2,147,483,648 to +2,147,483,647
float Floating-point numbers in the range of ±3.4 * 10-38 to ±3.4 * 1038, with 7 digits of
accuracy
double Floating-point numbers in the range of ±1.7 * 10-308 to ±1.7 * 10308, with 15 digits of
accuracy
char Can store integers in the range of -128 to +127. Typically used to store characters.
string Strings of text
bool Stores the values true or false

#include <iostream>
int main()
{
int age;
cout << "What is your age?" << endl;
cin >> age;
cout << "Here is the value that you entered:" << endl;
cout << age;
return 0;
}
Program Output
What is your age?
24 [Enter]
24
Read a value into the age variable

#include <iostream>
#include <string>
int main()
{
string name;
double payRate;
int hours;
cout << "Enter your first name." << endl;
cin >> name;
cout << "Enter your hourly pay rate." << endl;
cin >> payRate;
cout << "Enter the number of hours worked." << endl;
cin >> hours;
cout << "Here are the values that you entered:" << endl;
cout << name << endl;
cout << payRate << endl;
cout << hours << endl;
return 0;
}
Program Output
Enter your first name.
Connie [Enter]
Enter your hourly pay rate.
55.25 [Enter]
Enter the number of hours worked.
40 [Enter]
Here are the values that you entered:
Connie
55.25
40

• Using getline To Read String Input Containing Spaces
#include <iostream>
#include <string>
int main()
{
string name;
cout << "Please enter your name." << endl;
getline(cin, name);
cout << "Hello, " << name << endl;
return 0;
}
Program Output
Please enter your name.
Kate Smith [Enter]
Hello, Kate Smith

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus
Examples:
total = price + tax;
sale = price - discount;
population = population * 2;
half = number / 2;
leftOver = 17 % 3;

• Named constants – use the const key word in declarations:
const double INTEREST_RATE = 0.069;
This declares a double constant named INTEREST_RATE, set to the value 0.069.

// This is a line comment
/*
This is a multiline comment.
*/

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