Write a program in different programming languages

The ℉/℃ converter is a good example which is simple to understand and includes fundamental programming concepts. Every program will have

• input: how to take input from user
• output: how to show messages to the user
• how to do arithmetic calculations
• conditionals: how to do different things based on user's input
• variables: storing different values that can be anything and using them
• functions: creating reusable chunks of code that take input, do something with it, and return an output
• comments: messages that are meant for humans reading the code and the compiler/interpreter will ignore them
• how to include chunks of code written by others, or by yourself but in different files

C

C is the godfather language, it was there before many of the modern languages and has influenced their syntax as well. C++, Objective-C, and C# are all based on C. It's fair to say that these languages were created as a response to C, or improve C. Knowing C helps you understand the raison d'être for a lot of programming languages and programming concepts.

You would probably not understand what the fuss is all about with garbage collection, statically typed, object oriented, compiled, and so on unless you have encountered C. Or why do people call their files main.js and main.css even.

As a programmer who started with web development and JavaScript as her first languages, a lot of these concepts were confusing for me because i had a hard time understanding what the fuss was all about.

// need the Standard Library for input and output (i.e. the printf() and scanf() functions)
#include <stdio.h>

void main() {
  int inputFormat;
  float inputValue, convertedValue;

  printf("What format would you like to convert? \n");
  printf("  1. Fahrenheit \n");
  printf("  2. Celsius \n\n");
  printf("Enter 1 or 2: ");

  scanf("%d", &inputFormat);

  // Check if the user did not read the message
  // and was dumb enough to enter something other than 1 or 2
  if (inputFormat != 1 || inputFormat != 2) {
    printf("\nYou have provided an incorrect value. Please select 1 or 2: ");

    scanf("%d", &inputFormat);
  }

  printf("\nEnter the value you want to convert: ");
  scanf("%f", &inputValue);

  // the conversion formula is: °C = (°F − 32) × 5/9
  // or:  °F = (°C + 32) x 9/5

  if (inputFormat == 1) {
    convertedValue = (inputValue - 32) * 5.0/9.0;
    printf("\n%.2f°F is equal to: %.2f°C \n", inputValue, convertedValue);
  } else {
    convertedValue = inputValue * (9.0/5.0) + 32;
    printf("\n%.2f°C is equal to: %.2f°F \n", inputValue, convertedValue);
  }

/*
NOTES:
- `printf()` prints to console
- `scanf()` reads from console
- `%d` is format specifier for decimal integer
- `%f` is format specifier for float
- `%.2f` means float with two decimal points

!! integer division yields an integer result !!
e.g. 7/4 will equal 1 and 19/4 will equal 4
that's why you have to keep the values in floats, for the maths to work
*/
}

# install compiler (linux)
sudo apt update && sudo apt install build-essential

# compile
cc fahrenheit_celsius_converter.c -o fahrenheit_celsius_converter

# run
./fahrenheit_celsius_converter

JavaScript

JavaScript's syntax is heavily inspired by C++ and Java. You don't need to type things, it'll infer if it's a string or an integer. You don't need to compile your code beforehand. You don't need to end every statement with a semicolon ;. If you do, good for you. If you don't, it'll figure it out with ASI (ASI stands for Automatic Semicolon Insertion). Whitespace doesn't matter.

# install JS runtime (linux)
# i prefer Deno over Node
curl -fsSL https://deno.land/install.sh | sh

# run
deno run fahrenheit_celsius_converter.js

Python

Python code look like a breath of fresh air. No semicolons, no curly braces. Whitespace matters and it'll determine code blocks based on indentation. Like JS, you don't have to type your variables.

# Python3 comes preinstalled on Ubuntu

# run
python3 fahrenheit_celsius_converter.py

Dart

Dart supports dynamic and static typing both. Meaning it's cool if you type your variables, but if you don't it'll infer them. It also has null safety, which means that a variable's value can not be null unless you explicitly tell it so.

• main() is mandatory

sudo apt-get update && sudo apt install apt-transport-https
wget -qO- https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo gpg --dearmor -o /usr/share/keyrings/dart.gpg
echo 'deb [signed-by=/usr/share/keyrings/dart.gpg arch=amd64] https://storage.googleapis.com/download.dartlang.org/linux/debian stable main' | sudo tee /etc/apt/sources.list.d/dart_stable.list

sudo apt-get update && apt-get install dart
echo 'export PATH="$PATH:/usr/lib/dart/bin"' >> ~/.profile