Introduction

 What is programming?
 Why should I learn programming?
 Course Outline
 Introduction to Programming Language
 Introduction to Pascal
 ‘Hello world!’
 ‘Hello, <your name>!’
 Variables

 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)

 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

 Introduction
 Pascal Syntax – I
 Pascal Syntax – II
 Pascal Syntax – III (depends on schedule)
 Algorithms – I
 Algorithms – II (depends on schedule)
 HTML
 CSS
 PHP
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 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

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

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

 Analysis
 program hello;
 ‘;’ : to separate different statements
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‘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.

 Analysis (cont.)
 var a : integer;
 ‘var’ : a special keyword, to notify the following statements are declaration of variables
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‘a’: the name of the variable
‘:’: declare ‘a’ is which type of variable
‘integer’: a type of variable, which is integers (with range
-32768..32767)
* 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.

 Analysis
 begin writeln(‘Hello, world!’); end.
 ‘begin’ : to specify the beginning of the program
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‘writeln’ : a function, to write the value then with a line break
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* 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.
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* writeln(‘Hello’); and writeln(Hello);
‘end.’: to specify the end of the program

 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.

 Analysis
 var name:string;
 ‘string’ : a type of variable, which is the compilation of characters
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‘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;
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Note that ‘’ is added to state that the values inside is a string!
 a := a + 1 is possible!

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

 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,’);

 Integral types (0, 1, 2, 3, …)
 Shortint (-128..+127)
 Byte (0..255)
 Integer (-32768..+32767)
 Word0 (-65536..65535)
 Longint(-2146473648..+2146473647)
 Floating point types (0.1, 0.23, etc.)
 Real
 Double

 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;

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Non-numerical
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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
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 chr(x); ord(c); delete(str, x, y); fillchar(str, x, c);
Convert ASCII code (x) into character
Convert character (c) into ASCII code length(str); copy(str, x, y); pos(substr, str);
Find the length of a string (str)
Copy, starting from the x th element, y elements of string (str) val(str, x, e); str(x, str);
Find position of substr in str
Convert a string (str) into an integer (x)
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, starting from xth element, y elements of string (str)
Fill the string (str) with a character (c) until string is (x-1) long

 Pascal compilers:
 Free Pascal (Official HKOI/CCC compiler)
 Dev-Pascal
 Quick Pascal
 Useful software:
 Notepad++
 Useful website/contact:
 http://www2.dbs.edu.hk/club-soc/ecs
 Lin Yin Long (L6D)