How a Program Works?
Tags: programming, python, tutorial, beginners
Published: 2023-10-24 20:29:12

## A Step-by-Step Journey into the World of Programming 🧩💡"

**Programming** is the process of writing instructions in a specific language for computers to execute tasks. It's essential because it equips individuals with problem-solving skills, enabling them to break down complex issues into manageable steps. It automates repetitive tasks, increasing efficiency and reducing errors. Programming fosters innovation, empowering people to create software, websites, and more. It's a gateway to diverse career opportunities in technology and beyond. Understanding programming is crucial in today's tech-driven world, fostering digital literacy and informed decision-making. It allows for creative expression, enabling individuals to bring their ideas to life. Learning programming future-proofs individuals by equipping them with skills vital in our increasingly digitalized society.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/bypx2rmf5ldz50zz9ka2.gif)

Programming involves identifying a problem, designing an algorithm, creating a flowchart to visualize the steps, writing pseudocode to bridge the gap between the algorithm and actual code, choosing a programming language, writing the code, testing, and debugging, with a focus on user interaction and ongoing development


## Let's walk through how programming works from beginning to end with the example of drawing a square


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/6q9r9ty9n942i85z7kv4.gif)

Programming begins with _**problem identification**_ : in this case, drawing a square. We then devise an _**algorithm**_, breaking the task into clear steps. A _**flowchart**_ visually represents this logic, ensuring clarity. _**Pseudocode**_ bridges the gap between the algorithm and actual code, using human-friendly language. After _**choosing a programming language**_ like Python, we write code, instructing a computer to draw a square. Code is then either _**compiled or interpreted**_ . Thorough _**testing and debugging**_ ensure it functions correctly. When _**executed**_ , the program draws a square. _**Documentation**_ adds context and explanations. In more complex projects, _**deployment**_ makes the program accessible, _**user feedback**_ leads to improvements, and the _**cycle continues**_

## 1. Problem Identification and Definition

 The programming process starts with identifying a problem or task that needs to be solved. This could be anything from creating a simple calculator to designing a complex video game

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8a2c3y3sshmr27qxyhqg.jpeg)

 Imagine a program as a special set of instructions that can make the computer draw a square on the screen

**Problem: "Draw a square."**

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9zgtla9oq481f68du2p7.jpeg)

## 2. Algorithm Design

 An algorithm is a step-by-step set of instructions or a well-defined procedure for solving a specific problem or accomplishing a particular task.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/jqk2au501yh1rhc0h1le.jpeg)

 In other words When you draw a square, you follow a set of steps – this is your algorithm!

**Algorithm :**

```javascript
1. Start at a specific point (0, 0).
2. Lift the drawing pen to avoid marking the paper.
3. Move the pen to the starting point of the square (e.g., (50, 50)).
4. Lower the pen to start drawing.
5. For i in range(4):
Move the pen forward by a certain distance (e.g., 100 units).
Turn the pen 90 degrees to the right.
6. Lift the pen to stop drawing.
7. Stop.
```
Here's a more detailed explanation of each step:

_**1. Start at a specific point (0, 0):**_ This instruction establishes the initial position for drawing. You begin at the point (0, 0), which is often considered the origin.

_**2. Lift the drawing pen to avoid marking the paper:**_ Before you start drawing the square, you lift the pen off the paper or disengage drawing mode to prevent any marks on the paper.

_**3. Move the pen to the starting point of the square (e.g., (50, 50)):**_ You move the pen to the desired starting point for the square. In this case, it's set to (50, 50). This action is similar to positioning the pen or cursor at the top-left corner of where you want to draw the square.

_**4. Lower the pen to start drawing:**_ After positioning the pen at the starting point, you lower the pen or engage drawing mode, allowing the pen to make marks on the paper or screen.

_**5. For i in range(4):**_ This is a loop that will execute the following steps four times, creating four sides to form a square.

_**6. Move the pen forward by a certain distance (e.g., 100 units):**_ The pen moves forward by a specified distance, e.g., 100 units. This effectively draws one side of the square. The direction of movement depends on the current orientation of the pen, which is typically defined as the direction it's pointing.

_**7. Turn the pen 90 degrees to the right:**_ After drawing one side, you turn the pen 90 degrees to the right. This rotation prepares the pen for drawing the next side of the square. After the rotation, the pen is now pointing in a new direction.

_**8. Lift the pen to stop drawing:**_ Before moving the pen to the next corner, you lift the pen to disengage drawing mode, preventing any lines from being drawn while moving to the next corner.

_**9. Stop:**_ The algorithm concludes after all four sides of the square have been drawn.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4p2yc83prsjgppxnu55a.gif)

## 3. Flowchart Creation


A flowchart is a kind of map that uses shapes to show the order of steps in an algorithm. In a flowchart, different shapes represent different actions and decisions.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/uc187ovb5bgihrbpf7m1.jpeg)

 This flowchart helps you see the steps to draw a square, like following a map to create a picture


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/11w6607ivghd51v0towv.gif)

The flowchart you provided visually represents a simple algorithm. Here's a textual description of what the flowchart does:

**_1.Start:_** The algorithm begins at the "Start" point.
**_2. Lift Pen:_** This action implies that a pen or marker is being lifted, so it won't draw or mark on the surface.
_**3. Move to (50, 50):**_ The algorithm moves to the point with coordinates (50, 50) on the drawing surface.
_**4. Lower Pen:**_ The pen is lowered, which means it is now in contact with the drawing surface and ready to make marks.
_**5. Repeat (4 times):**_ This indicates a loop that will execute the following steps four times.
   _**a. Move Pen Forward by 100 units:**_ The pen moves forward by a specified distance, e.g., 100 units. This effectively draws one side of the square. The direction of movement depends on the current orientation of the pen, which is typically defined as the direction it's pointing
  _**b. Turn Pen 90 degrees to the right:**_ After drawing one side, you turn the pen 90 degrees to the right. This rotation prepares the pen for drawing the next side of the square. After the rotation, the pen is now pointing in a new direction.
  _**c. Loops repeats 4 times:**_ This loop (step 5) repeats four times in total, as specified.
_**6. Lift Pen:**_ After the loop is completed, the pen is lifted again.
_**7. Stop:**_ The algorithm ends, and the execution stops.

In a practical context, this flowchart might represent instructions for a robot or a computer program controlling a drawing machine. The machine starts by lifting the pen, moving to a specific location, lowering the pen, repeating a series of lifting and lowering the pen actions four times, and then lifting the pen again before stopping.

In flowcharts, different shapes represent different elements or actions. Here's a breakdown of the shapes used in the flowchart you've described:

_**Start/End:**_ "Start" and "Stop" are typically represented by oval shapes. They indicate the beginning and end of the algorithm or process.

_**Process:**_ "Lift Pen," "Move to (50, 50)," "Lower Pen", Move Pen Forward by 100 units & Turn Pen 90 degrees to the right are represented by rectangular shapes. These shapes denote specific actions or operations that need to be performed.

**Decision/Conditional**: The "Repeat (4 times)" indicates a loop or repetition. In flowcharts, loops or decisions are often represented by diamond shapes. In this case, it suggests that the actions within the loop will be repeated a specified number of times.

## 4. Pseudocode Development

A Pseudocode is like writing down your instructions using everyday words, just like taking notes.You can see the use of indentation and clear, step-by-step instructions. In an actual programming language, you would replace the plain language with code, but pseudocode is an excellent way to plan and design your program before writing the actual code.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9jesfiqzpblco8larvgj.jpeg)

In this pseudocode, we are using plain language to describe the steps needed to draw a square. 

```javascript
Start at (0, 0)
Lift Pen
Move to (50, 50)
Lower Pen
For i in range(4):
    Move Pen Forward by 100 units
    Turn Pen 90 degrees to the right
Lift Pen
Stop
```

In this pseudocode/programming language, you are instructing a pen to perform the following actions:

1. Start at the coordinates (0, 0).
2. Lift the pen (so it doesn't draw).
3. Move to the coordinates (50, 50).
4. Lower the pen (so it starts drawing).
5. Then, in a loop that runs 4 times:
   a. Move the pen forward by 100 units.
   b. Turn the pen 90 degrees to the right.
6. Lift the pen (stop drawing).
7. Stop.

This code appears to describe drawing a square with sides of 100 units each, starting from the point (50, 50) and ending at the same point. It's a basic example of how you can represent drawing instructions using a pseudocode-like language.

## 5. Choosing a Programming Language

Different programming languages are suited to different types of tasks. Programmers choose a language that is appropriate for the problem at hand. **_Block-based programming_** and _**Text-based programming**_ are two distinct approaches to coding, each with its own set of advantages and use cases. 


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/1uh1a2fotm2nrax56anm.jpeg)

_**Block-Based Programming:**_

**_Visual Programming:_** Block-based programming uses a visual interface where code is represented as blocks or puzzle pieces that can be manipulated, combined, and arranged to create programs. It's often used to teach coding to beginners, especially children.

_**No Syntax:**_ One of the main benefits of block-based programming is that it eliminates the need to write code in a specific programming language. Instead, users snap together blocks with predefined functions, variables, and logic.

_**Ease of Learning:**_ Block-based programming is very beginner-friendly. It lowers the barrier to entry for those who may find traditional text-based coding intimidating. It's often used in educational settings to teach programming concepts.

_**Widely Used in Education:**_ Platforms like Scratch, Blockly, and Tynker are popular for teaching kids and beginners the fundamentals of coding and computational thinking.

_**Limited Expressiveness:**_ Block-based programming can be limiting in terms of the complexity and breadth of programs that can be created. It's not well-suited for professional software development but serves as a great starting point.


Here are some popular block-based programming platforms and the languages they use:

 **_1. Scratch:_**

Language: Scratch
Description: Scratch is one of the most popular block-based programming platforms for beginners, particularly children. It uses its own visual language, where you snap together blocks to create scripts. It's used to create animations, games, and interactive stories.

_**2. Blockly:**_

Language: Blockly
Description: Blockly is an open-source library for building visual programming editors. It can be integrated into various applications and websites to create custom block-based programming environments. The language used depends on the specific implementation.

_**3. Tynker:**_

Language: Tynker
Description: Tynker offers a block-based programming environment designed for educational use. It uses a visual programming language that is similar to Scratch and is often used to teach kids how to code.

_**4. MIT App Inventor:**_

Language: Blocks in MIT App Inventor are used to create apps for Android devices. The language is designed to be accessible to non-programmers, and it's specific to app development.

_**5. LEGO Mindstorms:**_

Language: LEGO Mindstorms uses a block-based programming language that's specific to programming LEGO robotics. It's designed for creating programs to control robots built with LEGO kits.

_**6. Snap! (formerly BYOB):**_

Language: Snap!
Description: Snap! is an extended version of Scratch that offers more advanced features and is used to teach both beginners and more experienced programmers. It uses its own block-based language.


**_Text-Based Programming:_**

_**1. Traditional Coding:**_ Text-based programming involves writing code in a specific programming language using text editors or integrated development environments (IDEs). It's the standard method of programming for professionals and experienced coders.

_**2. Full Control:**_ Text-based programming provides full control over the code, algorithms, and data structures. Programmers can use any programming language that suits their needs.

_**3. Extensive Libraries and Ecosystem:**_ Text-based programming languages have extensive libraries and tools available, making it suitable for a wide range of applications, from web development to artificial intelligence.

_**4. Scalability and Performance:**_ Professional software development, system programming, and performance-critical applications are typically implemented using text-based programming languages because of their scalability and performance.

_**5. Steep Learning Curve:**_ Learning to write code in a specific programming language can be challenging, especially for beginners. It requires an understanding of syntax and logic.

Choosing a text-based programming language depends on your specific needs and goals. There are numerous programming languages available, each with its own strengths and use cases. Here are some popular text-based programming languages and their typical use cases:

**_1. Python:_**

Strengths: Readability, versatility, and a large standard library.
Use Cases: Web development, data science, machine learning, scripting, automation, scientific computing, and more.

_**2. JavaScript:**_

Strengths: The primary language for front-end web development, widely supported by browsers.
Use Cases: Building interactive websites, web applications, server-side development (Node.js), and game development (using libraries like Phaser or Three.js).

_**3. Java:**_

Strengths: Platform independence, strong typing, and used in enterprise software.
Use Cases: Building Android apps, enterprise applications, web applications, and embedded systems.

_**4. C++:**_

Strengths: High performance, low-level memory control, and strong typing.
Use Cases: Game development, system programming, performance-critical applications, and embedded systems.

_**5. C# (C-Sharp):**_

Strengths: Developed by Microsoft, it's used for Windows applications, game development, and web development.
Use Cases: Game development (Unity), Windows applications, and ASP.NET web applications.

_**6. Ruby:**_

Strengths: Readability, simplicity, and productivity.
Use Cases: Web development (Ruby on Rails), scripting, and automation.
PHP:

Strengths: Server-side scripting language designed for web development.
Use Cases: Server-side web development, creating dynamic web pages.

_**7. Swift:**_

Strengths: Designed for safety and performance, mainly used for iOS and macOS app development.
Use Cases: iOS and macOS application development.

_**8. Rust:**_

Strengths: Memory safety, system-level control, and modern features.
Use Cases: System programming, embedded systems, web development, and performance-critical applications.

_**9. Go (Golang):**_

Strengths: Simplicity, efficiency, and built-in support for concurrent programming.
Use Cases: Web servers, cloud-based applications, microservices, and network applications.

_**10. SQL (Structured Query Language):**_

Strengths: Specialized language for managing relational databases.
Use Cases: Database management, data analysis, data reporting.

## 6. Writing Code

Programmers write code, which is a series of commands and statements in the chosen programming language.Using the pseudocode and algorithm as a guide, programmers write the actual code in the chosen programming language. This involves translating the instructions into specific syntax and commands that the computer can understand and execute.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/j1hhz6l4vurqdlcin56x.jpeg)

## Using Scratch, a block-based visual programming language

In Scratch, a block-based visual programming language, you can create a program to draw a square using the following steps:

_**1. Open Scratch:**_ If you haven't already, open the Scratch programming environment on your computer or through the Scratch website (scratch.mit.edu).

**_2. Choose Sprite:_** You can use the default sprite (cat) or create your own. Click on the "Choose a Sprite from Library" or "Paint New Sprite" option to select or create a sprite to draw your square.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/owrzxjuenme2yhnnrrmg.png)



_**3. Programming the Sprite:**_

Select the sprite you want to use for drawing.
Add the following code blocks to your sprite:

```javascript
when green flag clicked
clear

repeat 4
forward (100) steps
turn right (90) degrees
```
The code above clears the drawing canvas and then uses a "repeat" loop to move the sprite forward by 100 steps and turn right by 90 degrees four times. This will create a square.


_**4. Running the Program:**_ Click the green flag to run your program. Your sprite will draw a square on the stage.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3yan3bejayb6bbtgth4l.png)


[To view the Program Click here] (https://scratch.mit.edu/projects/editor/?tutorial=getStarted)

This simple Scratch program instructs the sprite to draw a square by repeating the action of moving forward and turning right four times, creating each side of the square. You can customize the size of the square by changing the number of steps in the forward block.


## Using Python, a text-based visual programming language

You can use the Python programming language to draw a square using the popular turtle module. Here's a simple Python program to draw a square:

```javascript
import turtle

# Create a turtle screen
window = turtle.Screen()

# Create a turtle object
t = turtle.Turtle()

# Draw a square
for _ in range(4):
    t.forward(100)  # Move forward by 100 units
    t.right(90)  # Turn right 90 degrees

# Close the window on click
window.exitonclick()
```

In this program:

We import the turtle module to create graphics.
A `turtle.Screen()` is created to provide a canvas for drawing.
A `turtle.Turtle()` object named t is created to draw on the canvas.
The for loop instructs the turtle to move forward by 100 units and turn right by 90 degrees four times, effectively drawing a square.
The `window.exitonclick()` function is used to close the drawing window when you click on it.
Run this Python program, and a window with the square drawing will appear. You can customize the size of the square by changing the value in the `t.forward() `line.

[To view the Program Click here](https://replit.com/@vayolapradeep00/drawing-a-square)

## 6. Code Compilation or Interpretation

Depending on the language, code is either compiled (translated into machine code that the computer can execute directly) or interpreted (translated and executed line by line). The result is a runnable program.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/2pifhu9dqxfs899nitn0.jpeg)

Here's a brief explanation of the difference between compiled and interpreted languages:

_**Compiled Languages:**_ In compiled languages like C, C++, or Java, the source code is first translated into machine code or an intermediate bytecode by a compiler. This results in a binary executable or bytecode file that can be run directly by the computer's CPU or a virtual machine. Compilation happens before the code is executed, and any errors must be fixed during the compilation process.

_**Interpreted Languages:**_ In interpreted languages like Python, the source code is executed directly by an interpreter. The interpreter reads and executes the code line by line. If there are any syntax or runtime errors, they are typically reported when the interpreter encounters them during execution.

Python is an interpreted programming language. This means that Python code is executed line by line by the Python interpreter without the need for a separate compilation step.Python's interpreted nature makes it easy to write and test code interactively. It also allows for greater flexibility and portability, as Python code can run on any system with a compatible interpreter without the need for recompilation. However, it can be slower than compiled languages for certain tasks because it doesn't produce highly optimized machine code.

To draw a square using Python, you can use a library like `turtle`. The `turtle` module provides a simple way to create graphics and draw shapes. Here's an example of how to draw a square using Python's `turtle` module:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

# Function to draw a square
def draw_square():
    for _ in range(4):
        pen.forward(100)  # Move the turtle forward by 100 units
        pen.right(90)     # Turn the turtle right by 90 degrees

# Draw the square
draw_square()

# Close the window on click
screen.exitonclick()
```

Now, let's talk about how code compilation or interpretation happens in this case:

**_1. Python Code Compilation/Interpretation:_**

- Python is an interpreted language, which means there is no separate compilation step before running the code.
- When you run the Python script, the Python interpreter reads and executes the code line by line.
- In this example, when you run the Python script, the interpreter reads each line of code in the script and performs the corresponding actions.

_**2. Drawing the Square:**_

- When the `draw_square` function is called, the Python interpreter executes the function line by line.
- It uses the turtle module to draw the square.
- The `pen.forward(100)` line moves the turtle forward by 100 units, and the `pen.right(90)` line turns the turtle right by 90 degrees, repeating these actions four times to create the square.

_**3. Displaying the Result:**_

- The `turtle` module creates a graphical window where the square is drawn.
- The `screen.exitonclick()` line keeps the window open until you click on it, allowing you to view the drawn square.
- In this case, there is no separate compilation step because Python is an interpreted language. The code is executed directly by the Python interpreter as you run the script.

## 6. Testing and Debugging

The program is tested to ensure it works as expected. Programmers may encounter errors or "bugs" that need to be identified and fixed. Debugging is the process of finding and correcting these issues.Testing and debugging are crucial aspects of the software development process that ensure your code works correctly and reliably. 

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/sm9voqakuy7gron7ebdx.jpeg)

Here's an overview of each and how they differ:

**_Testing:_**

**_Purpose:_** Testing is the process of verifying that your code functions as intended and meets its specified requirements. It involves systematically checking your code for correctness.

_**Types of Testing:**_

- **_Unit Testing:_** Tests individual components or functions in isolation to verify their correctness.
- **_Integration Testing:_** Checks how different components work together.
- _**System Testing:**_ Tests the entire system to ensure it me_**ets the overall requirements.
- User Acceptance Testing (UAT):**_ Involves end-users testing the software to ensure it meets their needs.

_**Approaches:**_

- _**Manual Testing:**_ Testers interact with the software manually, following test cases or exploring to find issues.
- _**Automated Testing: **_Testing is automated using test scripts or frameworks, which can run repetitive tests quickly and consistently.

_**Validation:**_ Testing helps validate that the software behaves correctly, produces expected results, and handles various inputs and conditions effectively.

_**Debugging:**_

_**Purpose:**_ Debugging is the process of identifying and fixing defects or "bugs" in your code. These bugs may lead to incorrect behavior or unexpected issues.

_**Activities:**_

- **_Error Identification:_** You locate and identify the source of the problem. This often involves observing incorrect behavior, analyzing error messages, and using debugging tools.
- _**Isolation:**_ Once you've identified the issue, you isolate it to a specific part of the code. This typically involves narrowing down the problematic section.
- _**Correction:**_ After isolating the problem, you make necessary code changes to correct it, addressing the root cause of the issue.

_**Validation:**_ Debugging aims to validate that the code is corrected and now functions as intended without the issue that was initially observed.

_**Relationship:**_

Testing and debugging are closely related but serve different purposes. Testing focuses on preventing issues by verifying that the code works as expected, while debugging is the process of fixing issues that have already been identified.

Testing is proactive and aims to catch issues before they reach production, while debugging is reactive and deals with issues that have been discovered in the development or production environment.

In practice, both testing and debugging are essential. Testing helps you catch and prevent issues early, while debugging is necessary for addressing issues that may slip through testing or arise in the production environment. The combination of effective testing and efficient debugging leads to more reliable and high-quality software.

Certainly! Here's an example of drawing a square using Python's `turtle` module and how testing and debugging can happen in this case:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

# Function to draw a square
def draw_square():
    for _ in range(4):
        pen.forward(100)  # Move the turtle forward by 100 units
        pen.right(90)     # Turn the turtle right by 90 degrees

# Testing:
# - The testing phase involves running the code to ensure it draws a square as expected.
# - After running the script, we visually inspect the output to see if it forms a square.
# - We may also test with different input values to ensure the square's size and shape are adjustable.

# Debugging:
# - If the square is not drawn correctly, debugging may be necessary.
# - Common debugging steps include:
#   1. Checking for syntax errors or typos in the code.
#   2. Verifying that the logic in the "draw_square" function is correct.
#   3. Inspecting variables and their values to identify issues.
#   4. Adding print statements to track the program's flow.
#   5. Correcting errors, if found, and retesting the code.

# Draw the square
draw_square()

# Close the window on click
screen.exitonclick()
```

In this example:

**_Testing_** involves running the script to ensure that it correctly draws a square. We visually inspect the output and may test it with different input values (e.g., changing the side length) to verify that the code behaves as expected.

_**Debugging**_ would come into play if the square is not drawn correctly. In a debugging scenario:

- We might check for syntax errors or typos in the code.
- We'd verify that the logic in the "`draw_square`" function is correct.
- We may inspect variables and their values to identify issues.
- Adding print statements can help track the program's flow and identify where things are going wrong.
- After identifying and correcting errors, we would retes
t the code to confirm that the square is drawn correctly.


Testing helps ensure the program behaves as intended, while debugging is the process of finding and correcting issues if they arise. In this case, debugging may involve tracing the logic and verifying that the turtle is moving and turning correctly to form a square.

## 7.Execution

The program is executed or run on a computer. It takes input, processes data, and produces output according to the instructions in the code. Execution refers to the process of running a computer program or script to perform a specific task or function. When you execute a program, the computer's CPU (Central Processing Unit) interprets and processes the instructions contained within the code, carrying out the operations defined by the program. 

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/i1upwr160okvhbg1ncl9.jpeg)

Here's an overview of program execution:

**_Source Code:_** Execution begins with the source code, which is the human-readable representation of the program written in a programming language. This source code needs to be translated into machine code for the computer to understand and execute.

_**Compilation or Interpretation:**_ For compiled languages (e.g., C, C++), the source code is compiled into binary machine code by a compiler before execution. The generated binary file is executed directly by the computer.
For interpreted languages (e.g., Python, JavaScript), the source code is executed by an interpreter, which translates and executes the code line by line. No separate compilation step is involved.

**_Execution of Instructions:_** The program's instructions are processed sequentially by the CPU. Each instruction is executed, and the CPU performs the necessary calculations and operations. This may involve data manipulation, control flow decisions, and interactions with external devices or data sources.

_**Memory and Data:**_ During execution, the program uses memory (RAM) to store data, variables, and program instructions. The CPU reads and writes data to and from memory as needed to carry out computations.

_**Input and Output:**_ Programs often interact with external entities through input and output operations. Input can come from sources like user input, files, or network connections, while output can be displayed on the screen, written to files, or sent to other devices.

_**Error Handling:**_ If an error occurs during execution, the program may terminate or handle the error gracefully, depending on how error handling is implemented in the code. Common error types include syntax errors, runtime errors, and logical errors.

_**Completion or Termination:**_ Execution continues until the program has completed its task, reached an exit point, or encountered an error that forces it to terminate. When execution ends, any allocated resources are typically released, and the program's state is finalized.

_**Results:**_ The program may produce results, which could be output data, a modified system state, or some form of response to the task it was designed to perform.

It's important to note that the execution of a program can vary depending on the programming language, the platform or environment in which it runs, and the specific task it is designed to accomplish. The debugging and testing processes are used to ensure that the program executes correctly and to identify and address any issues that may arise during execution.

To draw a square using Python with the `turtle` module, you can create a script as follows:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

# Function to draw a square
def draw_square():
    for _ in range(4):
        pen.forward(100)  # Move the turtle forward by 100 units
        pen.right(90)     # Turn the turtle right by 90 degrees

# Draw the square
draw_square()

# Close the window on click
screen.exitonclick()
```

Here's how execution happens in this case:

_**Importing Libraries:**_ The script begins by importing the `turtle ` module, which provides functions for creating graphics.

_**Creating a Screen:**_ A turtle graphics window is created using `turtle.Screen().` This window is where the square will be drawn.

_**Creating a Turtle:**_ An instance of a turtle is created with `turtle.Turtle().` This turtle is like a virtual pen that you can control to draw on the screen.

_**Defining a Function:**_ The draw_square function is defined. This function contains a loop that moves the turtle forward by 100 units and turns it right by 90 degrees four times, which creates a square.

_**Drawing the Square:**_ The draw_square function is called, and the `turtle` moves to draw a square on the screen.

_**Handling User Interaction:**_ The `screen.exitonclick()` method is used to keep the window open until the user clicks on it. This allows you to view the drawn square.

During execution, the Python interpreter interprets the code, and the turtle module takes care of the graphics. The execution involves drawing the square by moving the turtle forward and turning it as specified in the function. This graphical representation of the square is displayed on the screen created by the turtle module.

The execution in this case is interactive, as it waits for user interaction to close the window, and you can see the result on the screen once the program runs.

## 8. Documentation

Documentation is crucial. Programmers write comments and provide documentation to explain how the code works, making it easier for others (or even their future selves) to understand and modify the code.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/p364w3fhdsbmn0huu4dq.jpeg)

To draw a square using Python's turtle module and provide documentation for the code, you can add comments and docstrings to explain the purpose and usage of the code. 

Here's an example of drawing a square with documentation:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

# Function to draw a square
def draw_square():
    """
    Draws a square using the turtle graphics module.
    The square has sides of length 100 units.
    """
    for _ in range(4):
        pen.forward(100)  # Move the turtle forward by 100 units
        pen.right(90)     # Turn the turtle right by 90 degrees

# Draw the square
draw_square()

# Close the window on click
screen.exitonclick()
```

Here's how documentation happens in this case:

_**Comments:**_ Comments in Python start with the # symbol. They are used to provide brief explanations within the code. In this example, comments are used to provide short, inline explanations of each code line, such as creating a turtle screen and object.

_**Docstring:**_ The draw_square function is documented using a docstring. A docstring is a multi-line string enclosed in triple quotes ("""). It provides a detailed description of the function, its purpose, and how it should be used. In this case, the docstring explains that the function draws a square with sides of 100 units.

_**Readability**_: Documentation enhances the code's readability and helps other developers (or your future self) understand the purpose and usage of the code.

_**Usefulness:**_ Well-documented code is essential for collaboration, maintenance, and troubleshooting. It makes it easier for others to work with your code and for you to return to it after some time.

By adding comments and docstrings to your code, you provide clear explanations of what each part of the code does and how to use it. This promotes good programming practices and helps ensure that your code is understandable and maintainable.

## 9. Documentation

If the program is intended for public use, it's deployed to the target environment. This could be a website server, a mobile app store, or any other platform where users can access it

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zmxpwp3ec9ejrw4wnwv6.jpeg)

Drawing a square using Python's `turtle` module is a relatively simple task, and deploying the code mainly involves running it on your local machine. Deployment in this context is more about running and executing the code rather than deploying it to a production environment, as you might with a web application or server.

Here's how to draw a square using Python's `turtle` module and how deployment happens in this case:

_**1. Write the Python Code:**_
Create a Python script that utilizes the turtle module to draw a square. Here's the code from a previous example:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

# Function to draw a square
def draw_square():
    for _ in range(4):
        pen.forward(100)  # Move the turtle forward by 100 units
        pen.right(90)     # Turn the turtle right by 90 degrees

# Draw the square
draw_square()

# Close the window on click
screen.exitonclick()
```

**_2. Local Deployment:_**

Save the code in a Python script file with a `.py` extension, such as `draw_square.py.`
Open your command prompt or terminal.
Navigate to the directory where your Python script is located using the `cd` command (change directory).
Run the script by entering python `draw_square.py` in the command prompt.

_**3. Execution:**_

The script will be executed, and a window with the square drawn by the `turtle` module will appear.
You can interact with the window and close it by clicking on it when the square has been drawn.

Deployment, in this case, simply means running the Python script on your local machine to visualize the square using the turtle graphics. There's no need for web hosting or server deployment since the code doesn't serve web content or run as a service. It's a local program for drawing shapes using the turtle graphics library.

## 10. User Interaction

End-users interact with the program, providing input and receiving output. The program's purpose is to serve the needs of these users.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/pz7e8jxz1so4vusaqlh2.jpeg)

After the square is drawn, the `screen.exitonclick()` function is called. This function allows the user to close the window by clicking inside the window.
When you click inside the window, the program responds by closing the window, thus ending the user interaction.
This interaction makes the program more user-friendly, as it allows users to view the drawn square and then close the window at their convenience. The `exitonclick()` function is just one way to handle user interaction; you can customize the interaction to suit your specific needs, depending on the requirements of your application.


## 11. Feedback & Iteration:

Feedback from users may lead to further updates and improvements. The programming cycle continues, with new features and bug fixes.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/83edht099p4ivud0caud.jpeg)

To draw a square using Python's turtle module and incorporate user feedback and iteration into the code, you can create a program that repeatedly draws squares based on user input. 

Here's an example of how this can be done:

```javascript
import turtle

# Create a turtle screen
screen = turtle.Screen()

# Create a turtle object
pen = turtle.Turtle()

def draw_square(side_length):
    """
    Draws a square using the turtle graphics module.
    :param side_length: Length of each side of the square.
    """
    for _ in range(4):
        pen.forward(side_length)
        pen.right(90)

while True:
    try:
        # Get user input for the side length of the square
        side_length = float(input("Enter the side length of the square (or type 'q' to quit): "))
        if side_length <= 0:
            print("Side length must be a positive number.")
            continue

        # Draw the square based on user input
        draw_square(side_length)
    except ValueError:
        user_input = input("Invalid input. Enter a number for side length or 'q' to quit: ")
        if user_input.lower() == 'q':
            break

# Close the window on click
screen.exitonclick()
```
In this example, user feedback and iteration are incorporated as follows:

_**1. Drawing Squares Based on User Input:**_

The `draw_square` function draws a square with a side length specified by the user.
The code uses a loop to draw four squares, making a total of four iterations to complete one square.

**_2. User Input and Feedback:_**

The program prompts the user to enter the side length of the square. If the user enters a valid positive number, it proceeds to draw the square.
If the user enters an invalid input (e.g., a non-numeric value or a negative number), the program provides feedback, informs the user that the input is invalid, and continues to prompt for a valid side length.

_**3. Iteration Based on User Choice:**_

The program runs in an infinite loop `(while True)`, allowing the user to draw multiple squares one after another.
If the user enters 'q' (or any other input), they can choose to quit the program and exit the loop.
This code demonstrates how user feedback and iteration can be incorporated into a program that repeatedly draws squares based on user input. Users can keep drawing squares as long as they choose to, providing input for each square's side length.

[Click here to view the program & result](https://replit.com/@vayolapradeep00/draw-a-square)


In summary, programming is the process of creating sets of instructions (code) to solve problems or perform tasks. These instructions are based on algorithms and written in a programming language. The code is then executed, and the program interacts with users to achieve specific goals. The process is iterative and dynamic, with ongoing development and maintenance.