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diff --git a/pascal.html.markdown b/pascal.html.markdown new file mode 100644 index 00000000..28dcc10f --- /dev/null +++ b/pascal.html.markdown @@ -0,0 +1,206 @@ +--- +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. + +``` + |