National Diploma Unit 4 Introduction to Software Development Introduction to Programming Languages

A brief history Programming has its roots in the 19 th Century Mechanical looms were “programmed” using punched cards indicating the weaving pattern Charles Babbage worked on a device- the Analytical Engine, for performing complex calculations He employed an assistant to produce the first working programs for this device – her name was Ada Lovelace Ada is a programming language named in her honour

What is a program? Computers are very stupid! They need to be told to do things with very precise instructions Computers use binary code (“1”s and “0”s) This is called machine code and isn’t very easy for the programmer

Programming languages Since we don’t speak binary and computers don’t use our language, an intermediate form was developed Assembly language uses simple words to represent binary code This is specific depending on the type of CPU Not easy to follow – especially in a large program

Assembly Language A typical assembler program would read something like this: LOAD M ADD M SAVE M Think about what this program might be doing Complex calculations can take a long time to program in assembler However, it is possible to access the values of individual registers - difficult in high level programming

High level languages These use familiar words following a set pattern (the syntax) They are easier for us to learn They are more difficult for computers since our code has to be translated into binary

Example languages Pascal – procedural C – procedural VB – event driven Java – Object oriented C++ - Object oriented Smalltalk – Object oriented Only one of these is a pure O-O language – find out which

How computers run programs Firstly, your code needs translating into binary This can happen all at once before running the program –compiling Or it can happen a line at a time - interpreting

Where Visual Basic fits in It evolved from BASIC – Beginners All- Purpose Symbolic Instruction Code It was useful for learning programming but had a bad press because of its “spaghetti code” of “goto”s

Visual Basic appears Bill Gates was said to have been impressed with VB when it developed It was flexible enough to allow you to write programs quickly which do not have much code, or to write much larger applications Its real strength was that it took advantage of the Windows environment and responded to user events

Visual Basic evolves It was (and still is) an event- driven language However, to become even more powerful, VB has also become Object-based. This means that it supports many of the features of Object-Oriented languages such as C++ and Java The latest version VB.Net, is fully O-O compliant and gives greater web integration

Tasks Find 2 more procedural languages What are the principles of object oriented languages? What is a Very High Level Language? What systems are they used for? Find out some facts about the programming language COBOL