“Sequence control structure” refers to the line-by-line execution by which statements are executed sequentially, in the same order in which they appear in the program. They might, for example, carry out a series of read or write operations, arithmetic operations, or assignments to variables.

The sequence control structure is the simplest of the three fundamental control structures that you learned about here. The following program shows an example of statements that are executed sequentially.

## PHP

```<?php
echo "Enter a number: ";
\$a = trim(fgets(STDIN));

\$b = \$a * \$a;

echo "The square of ", \$a, " is ", \$b;
?>
```

## Java

```public static void main(String[] args) throws java.io.IOException {
double a, b;

System.out.print("Enter a number: ");

b = a * a;

System.out.println("The square of " + a + " is " + b);
}
```

## C++

```#include <iostream>
using namespace std;
int main() {
double a, b;

cout << "Enter a number: ";
cin >> a;

b = a * a;

cout << "The square of " << a << " is " << b;
return 0;
}
```

## C#

```static void Main() {
double a, b;

Console.Write("Enter a number: ");

b = a * a;

Console.Write("The square of " + a + " is " + b);
}

```

## Visual Basic

```Sub Main()
Dim a, b As Double

Console.Write("Enter a number: ")

b = a ^ 2

Console.Write("The square of " & a & " is " & b)

```a = int(input("Enter a number: "))