General Programming

Basics of programming

This section will discuss about the general things that applies to all programming languages. This includes ✍️

We will discuss each and how it applies to programming.

What is Programming

Program - Process of writing computer programs. Programs - written step by step instructions that guide users on how to do a specific task. You will be instructing the computer by giving specific instructions.

Definition Of Terms

Syntax - Rules of a programming language. Every language has there own rules just like our natural languages. e.g. terminate every line with a semicolon at the end.

Algorithms - Set of rules/instructions in problem solving. Step by step instructions for solving a problem.

Flowchart - Diagramatic representation of an algorithm

Variables

This is a computer storage location. Imagine asking a user for their names and store it in the computer's memory and you can call the memory location anywhere in the program to use it.

Variable Declaration is just giving name to a variable while Variable initialization is giving value to a variable

variables
// Variable Example
String Movie;  // variable declaration

Movie = "Avengers-End Game";   //variable initialisation

//variable declaration and initialisation
String MyPlatform = "Coding 101 Platform";

Rules of writing variables

Specific languages follow specific rules. This includes:

  • A variable cannot start with a number

  • A variable can start with a dollar sign ($), underscore(_) , capital or small letter.

  • variables are case-sensitive

  • Variables cannot have keywords

Constants

These are same with variables only that they don't change once initialised. Variables can be re-initialised but constants can't change.

// constants syntax
const PIE = 3.142;

// using the above constant
int area = 0.5 * PIE * 7 * 7;

Keywords

These are the reserved words used by a specific language to do something. Like above const is a reserved keyword for constants.

Note each language has specific keywords.

Data Types

There are a lot of data that we use to come up with programs. The most common include:

  • Integers - Include numbers e.g. int num1 = 100

  • Characters - ( char ) single lettered char 1st = 'r'

  • Strings - (string ) Combination of characters data types string MyName = "Nicanor"

  • Boolean - bool values required for true or false occasions.

  • Float - used for numbers but with decimal values float num2 = 5.434

  • Double - used for numbers with large decimal values double num = 5.4324343434343

  • Array - Collection of the same data types int numValues = [3, 2, 4, 5, 2, 43, 23]

  • Object - Data type which stores data and information on how to process that data e.g. const Names = { Name : "Nicanor" }

TypeOf Operator

Returns the type of argument. If you want to check the type of data type you using 

typeof "foo";
// result will be shown on the console after execution

Operators

This includes combination of more than one data type, preferably integers, float and double. These include

  • Arithmetic Operators - +, -, *, modulas(%), / .

  • Assignment Operator - = e.g. int x = 100;

  • Logical Operators - &&(AND) , OR(||), not(!)

  • Relational Operators- Used when making comparisons >, <, >=, <=, equal to(==), not equal to(!=) e.g. (10 >= 20) && ('c' == 'd')

More advanced operators include conditional Operator that uses ternary operator (?) e.g.

expression1 ? expression2 : expression3 ;

Comments

Used by programmers to explain their code. Cannot be read by the program during execution. Every language has its own syntax of writing comments e.g.

// this is a javascript/java comment
<!-- HTML Comment -->
# PHP comment

Conditionals Statements

Used to perform different actions based on different conditions. Based on making decisions. The diagram below shows if....else statement

The following are conditions we going to discuss about

  • If statement

  • If ... else statement

  • if ... else if ... statement

If Statement

Control statements that allows to make decisions and execute statements conditionally. Syntax is as follows:

if (expression) {
   Statement(s) to be executed if expression is true
}

// e.g
int x = 10;
if (x > 5) {
   print('x is greater than 5');
}

If ... else Statements

Allows execution of statements in a more controlled way. Syntax and an example

if (expression) {
   Statement(s) to be executed if expression is true
} else {
   Statement(s) to be executed if expression is false
}

// an example
int x = 10;
if (x > 5) {
   print('x is greater than 5');
} else {
   print('x is less than 5');
}

If ... else if ... Statements

Advanced form of If ... else statements that allows making correct decisions based on several conditions. Syntax is as below

if (expression 1) {
   Statement(s) to be executed if expression 1 is true
} else if (expression 2) {
   Statement(s) to be executed if expression 2 is true
} else if (expression 3) {
   Statement(s) to be executed if expression 3 is true
} else {
   Statement(s) to be executed if no expression is true
}

Switch Statements

This is an alternative of If ... else statements by minimising the repeated statements. Flowchart is as shown below

Syntax

switch (expression) {
   case condition 1: statement(s)
   break;
   
   case condition 2: statement(s)
   break;
   ...
   
   case condition n: statement(s)
   break;
   
   default: statement(s)
}
// Note - Default is there so that if all the other case won't execute
          Break is used to exit out of that case and stop execution

An example of Switch statements

char grade = 'A';
switch (grade) {
   case 'A': print("Good job<br />");
            break;

   case 'B': print("Pretty good<br />");
            break;

   case 'C': print("Passed<br />");
            break;

   case 'D': print("Not so good<br />");
            break;

   case 'F': print("Failed<br />");
            break;

   default:  print("Unknown grade<br />")
}

// Result
Good job

Functions

This is a group of code that does a specific thing. Also a group of re-usable code. Syntax 

function functionname(parameters) {
    // statements
}

Function Declaration is just like the above function syntax. Just writing group of codes to do specific task

Function Calling is using the function in other places. You just call the function name in several places that needs application. functionname(arguments)

Parameters are like variables that are passed into the function

Arguments are real values that will replaces the parameters and be used in the function.

<html>
   <head>  
      <script type = "text/javascript">
         function concatenate(first, last) {
            var full;
            full = first + last;
            return full;
         }
         function secondFunction() {
            var result;
            result = concatenate('Zara', 'Ali');
            document.write (result );
         }
      </script>      
   </head>
   
   <body>
      <p>Click the following button to call the function</p>      
      <form>
         <input type = "button" onclick = "secondFunction()" value = "Call Function">
      </form>      
      <p>Use different parameters inside the function and then try...</p>  
  </body>
</html>

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