Which Statement Lets the User Enter Data?

In PHP, data input is accomplished using the PHP statement

  $var_name = trim(fgets(STDIN));

where

• $var_name can be any variable.
• STDIN stands for STANDARD INPUT (this is usually the keyboard).
• function trim() is discussed later.

The following code fragment lets the user enter his or her name and age.

$name = trim(fgets(STDIN));
$age = trim(fgets(STDIN));
echo "Wow, you are already", age, "years old,", name, "!";

It could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

echo "What is your name?";
$name = trim(fgets(STDIN));

echo "What is your age?";
$age = trim(fgets(STDIN));

echo "Wow, you are already", age, "years old,", name, "!";

In Java, data input is accomplished using the following Java statements

  java.io.BufferedReader cin = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));

  String var_name_str;

  int var_name_int;

  long var_name_long;

  double var_name_dbl;

  //Read a string from the keyboard

  var_name_str = cin.readLine();

  //Read an integer from the keyboard

  var_name_int = Integer.parseInt(cin.readLine());

  //Read a long integer from the keyboard

  var_name_long = Long.parseLong(cin.readLine());

  //Read a real from the keyboard

  var_name_dbl = Double.parseDouble(cin.readLine());

where

• var_name_str can be any variable of type String.
• var_name_int can be any variable of type int.
• var_name_long can be any variable of type long.
• var_name_dbl can be any variable of type double.

The following code fragment lets the user enter his or her name and age.

java.io.BufferedReader cin = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));
String name;
int age;

name = cin.readLine();
age = Integer.parseInt(cin.readLine());
System.out.print("Wow, you are already" + age + "years old," + name + "!");

It could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

java.io.BufferedReader cin = new java.io.BufferedReader(new java.io.InputStreamReader(System.in));

String name;
int age;

System.out.print("What is your name? ");
name = cin.readLine();

System.out.print("What is your age? ");
age = Integer.parseInt(cin.readLine());

System.out.print("Wow, you are already" + age + "years old," + name + "!");

In C++, data input is accomplished using the following C++ statements

  //Read a number or a string (without spaces or tabs) from the keyboard

  cin >> var_name;

  //Read a string that includes spaces and tabs from the keyboard

  getline(cin, var_name_str);

where

• var_name can be a variable of any type.
• var_name_str can be any variable of type string.

Notice: Please note that cin considers space characters as terminating characters when reading a string from the keyboard. Thus, reading a string with cin means to always read a single word, not a phrase or an entire sentence. To read an entire line you can use the getline() function.

The statement cin can also be used to request more than one value. The following code fragment lets the user enter his or her name and age.

string name;
int age;

cin >> name >> age;

cout << "Wow, you are already" << age << "years old," << name << "!");

However, it could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

string name;
int age;

cout << "What is your name? ";
cin >> name;

cout << "What is your age? ";
cin >> age;

cout << "Wow, you are already" << age << "years old," << name << "!");

In C#, data input is accomplished using the following C# statements

  string var_name_str;

  short var_name_short;

  int var_name_int;

  long var_name_long;

  double var_name_dbl;

  //Read a string from the keyboard

  var_name_str = Console.ReadLine();

  //Read a short integer from the keyboard

  var_name_short = Int16.Parse(Console.ReadLine());

  //Read an integer from the keyboard

  var_name_int = Int32.Parse(Console.ReadLine());

  //Read a long integer from the keyboard

  var_name_long = Int64.Parse(Console.ReadLine());

  //Read a real from the keyboard

  var_name_dbl = Double.Parse(Console.ReadLine());

where

• var_name_str can be any variable of type string.
• var_name_short can be any variable of type short.
• var_name_int can be any variable of type int.
• var_name_long can be any variable of type long.
• var_name_dbl can be any variable of type double.

The following code fragment lets the user enter his or her name and age.

string name;
byte age;

name = Console.ReadLine();
age = Byte.Parse(Console.ReadLine());
Console.Write("Wow, you are already" + age + "years old," + name + "!");

However, it could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

string name;
byte age;

Console.Write("What is your name? ");
name = Console.ReadLine();

Console.Write("What is your age? ");
age = Byte.Parse(Console.ReadLine());

Console.Write("Wow, you are already" + age + "years old," + name + "!");

In Visual Basic, data input is accomplished using the following Visual Basic statements

  Dim var_name_str As String

  Dim var_name_short As Short

  Dim var_name_int As Integer

  Dim var_name_long As Long

  Dim var_name_dbl As Double

  'Read a string from the keyboard

  var_name_str = Console.ReadLine()

  'Read a short integer from the keyboard

  var_name_short = Console.ReadLine()

  'Read an integer from the keyboard

  var_name_int = Console.ReadLine()

  'Read a long integer from the keyboard

  var_name_long = Console.ReadLine()

  'Read a real from the keyboard

  var_name_dbl = Console.ReadLine()

where

• var_name_str can be any variable of type String.
• var_name_short can be any variable of type Short.
• var_name_int can be any variable of type Integer.
• var_name_long can be any variable of type Long.
• var_name_dbl can be any variable of type Double.

The following code fragment lets the user enter his or her name and age.

Dim name As String
Dim age As Byte

name = Console.ReadLine()
age = Console.ReadLine()
Console.Write("Wow, you are already" & age & "years old," & name & "!")

However, it could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

Dim name As String
Dim age As Byte

Console.Write("What is your name? ")
name = Console.ReadLine()

Console.Write("What is your age? ")
age = Console.ReadLine()

Console.Write("Wow, you are already" & age & "years old," & name & "!")

In Python, data input is accomplished using one of the following statements:

  #Read a string from the keyboard

  var_name_str = input([prompt])

  #Read an integer from the keyboard

  var_name_int = int(input([prompt]))

  #Read a real from the keyboard

  var_name_float = float(input([prompt]))

where

• prompt is the prompt message to be displayed. It can be either a variable or a string enclosed in single or double quotes. The argument prompt is optional.
• var_name_str can be any variable of type string.
• var_name_int can be any variable of type integer.
• var_name_float can be any variable of type float.

Notice: Functions int() and float() are discussed later.

The following code fragment lets the user enter his or her name and age.

name = input()

age = int(input())

print("Wow, you are already", age, "years old,", name, "!")

However, it could be even better if, before each data input, a “prompt” message is displayed. This makes the program more user-friendly. For example, look at the following program.

name = input("What is your name? ")

age = int(input("What is your age? "))

print("Wow, you are already", age, "years old,", name, "!")

Now when a user executes your program he or she knows exactly what to enter!

The example that follows is equivalent to the previous one.

print("What is your name? ", end = "")
name = input()

print("What is your age? ", end = "")
age = int(input())

print("Wow, you are already", age, "years old,", name, "!")

Notice: In Python, it is recommended to display prompt messages using the input() statement.