## C# `for` Loop: Explanation, Theory, and Examples
### Explanation
A `for` loop in C# is a control flow statement that allows code to be executed repeatedly based on a boolean condition. It is typically used when the number of iterations is known before entering the loop.
### Theory
The `for` loop in C# consists of three main parts:
1. **Initialization**: This step is executed once before the loop starts. It typically initializes one or more loop control variables.
2. **Condition**: This boolean expression is evaluated before each iteration of the loop. If the condition is true, the loop body is executed; if false, the loop terminates.
3. **Iteration**: This step is executed after each iteration of the loop body. It typically updates the loop control variables.
The basic syntax of a `for` loop in C# is:
```csharp
for (initialization; condition; iteration)
{
// Code to be executed
}
```
### Diagram
Here is a flowchart representing the C# `for` loop:
```
+--------------------+
| Initialization |
+--------------------+
|
v
+--------------------+
| Condition |
+--------------------+
|
+-------------+------------+
| | |
| true | false |
| v |
| +----------------+ |
| | Execute Code | |
| +----------------+ |
| | |
| v |
| +----------------+ |
+-----> Iteration +---+
+----------------+
```
### Examples
#### Example 1: Printing Numbers from 1 to 5
Here is an example of a `for` loop in C# that prints numbers from 1 to 5:
```csharp
using System;
class Program
{
static void Main()
{
for (int i = 1; i <= 5; i++)
{
Console.WriteLine(i);
}
}
}
```
**Explanation**:
- **Initialization**: `int i = 1;` initializes the loop control variable `i` to 1.
- **Condition**: `i <= 5;` continues the loop as long as `i` is less than or equal to 5.
- **Iteration**: `i++` increments `i` by 1 after each iteration.
**Output**:
```
1
2
3
4
5
```
#### Example 2: Iterating Over an Array
Here is an example of a `for` loop in C# that iterates over an array of fruits and prints each one:
```csharp
using System;
class Program
{
static void Main()
{
string[] fruits = { "apple", "banana", "cherry" };
for (int i = 0; i < fruits.Length; i++)
{
Console.WriteLine(fruits[i]);
}
}
}
```
**Explanation**:
- **Initialization**: `int i = 0;` initializes the loop control variable `i` to 0.
- **Condition**: `i < fruits.Length;` continues the loop as long as `i` is less than the length of the `fruits` array.
- **Iteration**: `i++` increments `i` by 1 after each iteration.
**Output**:
```
apple
banana
cherry
```
#### Example 3: Calculating the Sum of Array Elements
Here is an example of a `for` loop in C# that calculates the sum of numbers in an array:
```csharp
using System;
class Program
{
static void Main()
{
int[] numbers = { 1, 2, 3, 4, 5 };
int sum = 0;
for (int i = 0; i < numbers.Length; i++)
{
sum += numbers[i];
}
Console.WriteLine("Sum: " + sum);
}
}
```
**Explanation**:
- **Initialization**: `int i = 0;` initializes the loop control variable `i` to 0.
- **Condition**: `i < numbers.Length;` continues the loop as long as `i` is less than the length of the `numbers` array.
- **Iteration**: `i++` increments `i` by 1 after each iteration.
- **Sum Calculation**: `sum += numbers[i];` adds the current array element to `sum`.
**Output**:
```
Sum: 15
```
### Summary
A `for` loop in C# is a powerful construct for iterating over sequences and executing code repeatedly based on a specified condition. It consists of initialization, condition, and iteration parts, making it versatile for a wide range of applications from simple counting to complex data processing.
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