1. Programming for Beginners
Lecture 1: Introduction: Program Structure & Java Syntax
Martin Nelson
Elizabeth FitzGerald

2. Aims & objectives of this course
Write your own programmes in a procedural language
Understand basic concepts such as procedural logic, variables, flow control, input and output principles
Identify important programming concepts

3. Course website
Course materials, exercises and useful web links can be found at:

4. Session 1 - aims & objectives
Appreciate how computer programs are constructed
Understand the differences between:
Compiled and interpreted languages
Procedural and object-oriented languages
Find out the basics of Java programming
Write a few simple programs making use of statements, comments and basic arithmetic

5. Computer programmes Set of instructions for the CPU Assembly language
“Switch settings”
Machine language
Assembly language
Mnemonics representing binary code
Assembler
3rd generation languages
“High level” languages
Compiled or interpreted (or both!)

6. High Level Languages (3GL)
Examples:
Fortran
COBOL
Pascal C
C++ C#
Java

7. Program construction Computers are 'stupid'
Mathematical and logical instructions are executed very quickly and accurately
They obediently but stupidly do what you tell them to – not necessarily what you want them to!
Tiny errors in a program can cause major problems when it is executed
Careful planning is essential
Flow charts are a useful tool to represent program flow visually

8. Algorithms
Algorithm = how you go about solving a puzzle; your solution to a task
Example: how do you make a cup of tea?
In programming, you should plan your algorithm before you start coding
Boil kettle
Put tea in cup
Pour boiling water into cup

9. Tea-making program – 1 Is kettle full? Fill kettle Boil kettleNo
Is kettle full?
Fill kettle
Yes
Boil kettle
Put tea in cup
Pour boiling water into cup

10. Elements of tea-making program
Fill kettle
Open tap
Wait
Is kettle full?
Yes No
Close tap
Place kettle under tap
Has kettle boiled?
Pour water into cup
Boil kettle
Switch kettle on
Wait No
Yes
Plug kettle into electrical socket

11. Tea-making program – 2 Is kettle full? Put tea in cup No Yes
Pour boiling water into cup

12. Now for some jargon… Compiled vs interpreted languages
(… but don’t worry about this too much  )
Compiled vs interpreted languages
Handy hint: If you’re not sure what these and other words mean, look at the ‘Glossary’ section of the course website

13. Compiled languages Data storage Source code Machine code CPU/memory
Compiler
Program execution

14. Interpreted languages
Data storage
Source code
CPU/memory
Interpreter
Machine code
Program execution

15. Compiled vs interpreted
Development more cumbersome
Easy to distribute
Machine code generated at compile time e.g. most high-level languages
Interpreted
Easy to develop
Distribution of interpreter required
Machine code generated at runtime e.g. BASIC, LISP, Perl

16. The Java model Java is an object-oriented high level language
"write once, run anywhere"
It is both compiled and interpreted
Java source code has .java extension
Source code is compiled to produce a .class file (bytecode) – not human-readable
Bytecode is interpreted by the Java VM (virtual machine)

17. How Java works Data storage CPU/memory Interpreter Compiler
Bytecode myprogram.class
Source code myprogram.java
CPU/memory
Interpreter
Compiler
Machine code
Program execution

18. A bit more jargon… Procedural vs object-oriented programmes
(… nearly finished though  )
Procedural vs object-oriented programmes
What is all this object-oriented stuff about?
Does it matter?
Does it mean anything?

19. Procedural vs object-oriented
Early high-level languages
Contain functions (or sub-routines) written and used inside the main program
Cannot use external functions easily
Object-oriented (OO)
Later high-level languages
Contain methods (or functions) and variables that can be written in main or external programs
Can call external functions or variables easily

20. Some examples Procedural Fortran COBOL (old versions) Pascal C Perl
Object-oriented (OO)
COBOL (latest version)
Delphi
C++ C#
Java
Visual Basic
Perl

21. What’s Java all about then?
NOT the same as JavaScript
Java SDK consists of 2 components:
Java VM (Virtual Machine)
Java API (Application Programming Interface) + accompanying documentation
If you alter your code you need to re-compile it before you can run the program
ONLY use Java version 2 and above (Java 1.2/Java 1.3/Java 1.4 etc)

22. On with the code! Quick intro to using Java
Then YOU start to code your first Java program!

23. Writing your first Java program
Use a text editor to write the source code
Save it as a .java file
Compile it using Java SDK on Granby
You need to have a Granby account before you can start writing your programs – if you haven't you will need to apply for one as soon as possible!

24. 'Hello world' program in Java
class myprog {
public static void main(String[] args)
System.out.println(“Hello world!”); }

25. Be careful what you type!
If you type something wrong, your code will either give you an error or won’t work properly.
If you get an error, check the following:
Capital letters are different to lower case – don’t mix them up.
{ }, ( ) and [ ] all do different things – have you used the right one?
Some lines need to end with a semi-colon – miss them off and your code won’t work.

26. Code Presentation Tips – 1
Indent code inside curly braces
Every time you open a pair of curly braces, indent the next line by 1 tab or three/four spaces.
When you close braces, unindent.
You can then see straight away if you have a brace missing.
class myprog {
Some code
Some more code
New braces, so indent again. }
More code

27. Code Presentation Tips – 2
You can add comments to your code to remind you (or someone else) how the code works.
Comments are ignored by the compiler.
On a single line, anything after // will be ignored.
Over many lines, anything between /* and */ will be ignored.
/* This is my first java code
* I really enjoyed writing it – I hope you like it */
class myprog {
public static void main(String[] args)
// The following line will say hello
System.out.println(“Hello!”); }

28. Code Presentation Tips – 3
Comments should be brief and helpful.
No need to add comments which state the obvious.
Blank lines help to make the code readable – use them to separate each of the code’s tasks.

29. Coming up in Session 2... Using variables to store information.
An introduction to the range of data types available.