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+---
+language: Pascal
+filename: learnpascal.pas
+contributors:
+ - ["Ganesha Danu", "http://github.com/blinfoldking"]
+ - ["Keith Miyake", "https://github.com/kaymmm"]
+---
+
+
+>Pascal is an imperative and procedural programming language, which Niklaus Wirth designed in 1968–69 and published in 1970, as a small, efficient language intended to encourage good programming practices using structured programming and data structuring. It is named in honor of the French mathematician, philosopher and physicist Blaise Pascal.
+source : [wikipedia](https://en.wikipedia.org/wiki/Pascal_(programming_language))
+
+
+
+to compile and run a pascal program you could use a free pascal compiler. [Download Here](https://www.freepascal.org/)
+
+```pascal
+//Anathomy of a Pascal Program
+//this is a comment
+{
+ this is a
+ multiline comment
+}
+
+//name of the program
+program learn_pascal; //<-- dont forget a semicolon
+
+const
+ {
+ this is where you should declare constant values
+ }
+type
+ {
+ this is where you should delcare a custom
+ data-types
+ }
+var
+ {
+ this is where you should declare a variable
+ }
+
+//main program area
+begin
+ {
+ area to declare your instruction
+ }
+end. // End of a main program area should required a "." symbol
+```
+
+```pascal
+//declaring variable
+//you can do this
+var a:integer;
+var b:integer;
+//or this
+var
+ a : integer;
+ b : integer;
+//or this
+var a,b : integer;
+```
+
+```pascal
+program Learn_More;
+//Lets learn about data types and their operations
+
+const
+ PI = 3.141592654;
+ GNU = 'GNU's Not Unix';
+ // constants are conventionally named using CAPS
+ // their values are fixed and cannot be changed during runtime
+ // holds any standard data type (integer, real, boolean, char, string)
+
+type
+ ch_array : array [0..255] of char;
+ // arrays are new 'types' specifying the length and data type
+ // this defines a new data type that contains 255 characters
+ // (this is functionally equivalent to a string[256] variable)
+ md_array : array of array of integer;
+ // nested arrays are equivalent to multidimensional arrays
+ // can define zero (0) length arrays that are dynamically sized
+ // this is a 2-dimensional array of integers
+
+//Declaring variables
+var
+ int, c, d : integer;
+ // three variables that contain integer numbers
+ // integers are 16-bits and limited to the range [-32,768..32,767]
+ r : real;
+ // a variable that contains a real number data types
+ // reals can range between [3.4E-38..3.4E38]
+ bool : boolean;
+ // a variable that contains a Boolean(True/False) value
+ ch : char;
+ // a variable that contains a character value
+ // char variables are stored as 8-bit data types so no UTF
+ str : string;
+ // a non-standard variable that contains a string value
+ // strings are an extension included in most Pascal compilers
+ // they are stored as an array of char with default length of 255.
+ s : string[50];
+ // a string with maximum length of 50 chars.
+ // you can specify the length of the string to minimize memory usage
+ my_str: ch_array;
+ // you can declare variables of custom types
+ my_2d : md_array;
+ // dynamically sized arrays need to be sized before they can be used.
+
+ // additional integer data types
+ b : byte; // range [0..255]
+ shi : shortint; // range [-128..127]
+ smi : smallint; // range [-32,768..32,767] (standard Integer)
+ w : word; // range [0..65,535]
+ li : longint; // range [-2,147,483,648..2,147,483,647]
+ lw : longword; // range [0..4,294,967,295]
+ c : cardinal; // longword
+ i64 : int64; // range [-9223372036854775808..9223372036854775807]
+ qw : qword; // range [0..18,446,744,073,709,551,615]
+
+ // additional real types
+ rr : real; // range depends on platform (i.e., 8-bit, 16-bit, etc.)
+ rs : single; // range [1.5E-45..3.4E38]
+ rd : double; // range [5.0E-324 .. 1.7E308]
+ re : extended; // range [1.9E-4932..1.1E4932]
+ rc : comp; // range [-2E64+1 .. 2E63-1]
+
+Begin
+ int := 1;// how to assign a value to a variable
+ r := 3.14;
+ ch := 'a';
+ str := 'apple';
+ bool := true;
+ //pascal is not a case-sensitive language
+ //arithmethic operation
+ int := 1 + 1; // int = 2 overwriting the previous assignment
+ int := int + 1; // int = 2 + 1 = 3;
+ int := 4 div 2; //int = 2 division operation where result will be floored
+ int := 3 div 2; //int = 1
+ int := 1 div 2; //int = 0
+
+ bool := true or false; // bool = true
+ bool := false and true; // bool = false
+ bool := true xor true; // bool = false
+
+ r := 3 / 2; // a division operator for real
+ r := int; // can assign an integer to a real variable but not the reverse
+
+ c := str[1]; // assign the first letter of str to c
+ str := 'hello' + 'world'; //combining strings
+
+ my_str[0] := 'a'; // array assignment needs an index
+
+ setlength(my_2d,10,10); // initialize dynamically sized arrays: 10×10 array
+ for c := 0 to 9 do // arrays begin at 0 and end at length-1
+ for d := 0 to 9 do // for loop counters need to be declared variables
+ my_2d[c,d] := c * d;
+ // address multidimensional arrays with a single set of brackets
+
+End.
+```
+
+```pascal
+program Functional_Programming;
+
+Var
+ i, dummy : integer;
+
+function factorial_recursion(const a: integer) : integer;
+{ recursively calculates the factorial of integer parameter a }
+
+// Declare local variables within the function
+// e.g.:
+// Var
+// local_a : integer;
+
+Begin
+ If a >= 1 Then
+ // return values from functions by assigning a value to the function name
+ factorial_recursion := a * factorial_recursion(a-1)
+ Else
+ factorial_recursion := 1;
+End; // terminate a function using a semicolon after the End statement.
+
+procedure get_integer(var i : integer; dummy : integer);
+{ get user input and store it in the integer parameter i.
+ parameters prefaced with 'var' are variable, meaning their value can change
+ outside of the parameter. Value parameters (without 'var') like 'dummy' are
+ static and changes made within the scope of the function/procedure do not
+ affect the variable passed as a parameter }
+
+Begin
+ write('Enter an integer: ');
+ readln(i);
+ dummy := 4; // dummy will not change value outside of the procedure
+End;
+
+Begin // main program block
+ dummy := 3;
+ get_integer(i, dummy);
+ writeln(i, '! = ', factorial_recursion(i));
+ // outputs i!
+ writeln('dummy = ', dummy); // always outputs '3' since dummy is unchanged.
+End.
+
+```
+