Introduction

In today’s session… What is programming? Why should I learn programming? Course Outline Introduction to Programming Language Introduction to Pascal ‘Hello world!’ ‘Hello, !’ Variables

What is programming? Process of writing, testing, debugging/troubleshooting, and maintaining the source code of computer programs (From Wikipedia) To create a program (software) for usage of a particular sort, e.g. word processor (e.g. Microsoft Word, OpenOffice.org Writer) for word processing (duh)

Why should I learn programming? Logic skills – very useful in Maths/Physics/Chemistry/… Understand more about computer / information systems Learn algorithms Learn how to type – fast! Represent the school in HKOI/CCC

Course Outline Introduction3/5 Pascal Syntax – I6/5 Pascal Syntax – II10/5 Pascal Syntax – III (depends on schedule)13/5 Algorithms – I17/5 Algorithms – II (depends on schedule)20/5 HTML24/5 CSS27/5 PHP31/5

Introduction to Programming Language Derived from human language Syntax – grammatical rules Symbol-like Lots: Pascal, A+, A++, B, C, C--, C++, C#, D, D#, E, F, F#, J, J++, J#, K, L, L++, M, Q, R, R++, S, T, X++, Y, Z, VB, ActionScript, PHP, FORTRAN, Java, Javascript, Python, etc. For different purposes and with different syntax / ideology behind programming

Introduction to Pascal ‘Educational’ Syntax are human-like, easy to understand Important in programming Have practical use despite criticisms

Hello, world! Classic approach to any programming language Objective: Print ‘Hello, world!’ Code: program hello; var a : integer; begin writeln(‘Hello, world!’); end.

Hello, world! Analysis program hello; ‘;’ : to separate different statements ‘program’ : a special keyword, to specify the name of the program ‘hello’: the name of the program * this statement can be ignored totally. * note any ‘name’ cannot be special keywords or start with numbers. E.g. program 3x; or program program; is not valid, but program _3x; or program _program; is valid.

Hello, world! Analysis (cont.) var a : integer; ‘var’ : a special keyword, to notify the following statements are declaration of variables ‘a’: the name of the variable ‘:’: declare ‘a’ is which type of variable ‘integer’: a type of variable, which is integers (with range ) * this statement can be ignored totally since this program has no use of variables * note program hello; var a : integer; is valid. * note var a, b, c : integer; is valid.

Hello, world! Analysis begin writeln(‘Hello, world!’); end. ‘begin’ : to specify the beginning of the program ‘writeln’ : a function, to write the value then with a line break * Try this out: writeln(‘Hello’); write(‘Hello’); writeln(‘Hello’); (What is the difference between writeln() and write() ?) writeln; is valid (what does this do?) ‘’’: to specify that the worlds ‘Hello, world!’ is a string, i.e. a series of characters, but not a variable. * writeln(‘Hello’); and writeln(Hello); ‘end.’: to specify the end of the program

Hello, ! Objective: Print ‘Hello,’, then the name of the user who has inputted his/her name in the first place. Code: program hello; var name : string; begin write(‘Please input your name: ’); readln(name); writeln(‘Hello, ‘, name, ‘!’); end.

Hello, ! Analysis var name:string; ‘string’ : a type of variable, which is the compilation of characters ‘name’: the name of variable of string * Variables come in different kinds, e.g. for integers, we have integer, longint, int64; for characters, we have char; for string, we have string, ANSIstring. * Each type of variables have different operations. * Variable can be assigned by ‘:=‘. E.g. name := ‘This is my name’ or a := 3; Note that ‘’ is added to state that the values inside is a string! a := a + 1 is possible!

Hello, ! Analysis readln(name); ‘readln’ : to request input of variable to the user ‘name’: the name of variable of string * Try read(name); instead of readln(name);, Or guess what’s the differences between readln and read.

Hello, ! Analysis writeln(‘Hello, ‘,name,’!’); ‘,’ is used to separate strings and values in the variable ‘name’ * writeln(‘H’,’e’,’l’,’l’,’o’,’,’,’ ‘,’); is equivalent to writeln(‘Hello,’);

Variables Integral types (0, 1, 2, 3, …) Shortint ( ) Byte (0..255) Integer ( ) Word0 ( ) Longint( ) Floating point types (0.1, 0.23, etc.) Real Double

Variables Operations of Integral / Floating point types ‘+’, e.g. c := a+b; ‘-’ e.g. c := a-b; ‘*’ e.g. c := a*b; ‘/’ e.g. c := a/b; ‘div’ e.g. c := a div b; ‘mod’ e.g. c := a mod b; ‘()’ e.g. c := (a + b)*a;

Variables Non-numerical Char (characters, e.g. ‘a’, ‘A’, ‘!’) String (an array of characters, usually max. at 255) Array (a collection of variable of specific types with index) <- covered later Operations chr(x); Convert ASCII code (x) into character ord(c); Convert character (c) into ASCII code length(str);Find the length of a string (str) copy(str, x, y); Copy, starting from the x th element, y elements of string (str) pos(substr, str);Find position of substr in str val(str, x, e);Convert a string (str) into an integer (x) str(x, str);Convert an integer (x) into a string (str) concat(str1, str2, …);Combine a string (str1) with another (str2, etc.) insert(str1, str2, x);Insert a string (str1) in the x th element of another (str2) delete(str, x, y); Delete, starting from xth element, y elements of string (str) fillchar(str, x, c); Fill the string (str) with a character (c) until string is (x-1) long

Last but not least… Pascal compilers: Free Pascal (Official HKOI/CCC compiler) Dev-Pascal Quick Pascal Useful software: Notepad++ Useful website/contact: Lin Yin Long (L6D)