History

Background

• Early programming code was what made the CPU in a computer work.

• They originally only worked for the one type of computer CPU.

• Different CPUs had different languages.

• All programming languages must be translated to 0s and 1s, for the CPU to carry out those instructions. 

• These instructions are code in binary using 0s and 1s  eg  0000 1101

• The more modern the programming language, the more people friendly it is to code.

• The older it is, the less people friendly, but more computer friendly to run.

• Programming languages are the symbols used to write code.

• They have started machine like and are now more like human natural language.

• All programming languages, even the most modern, translate to machine language.

• Some categorise these into First Generation Languages (GL), Second GL, Third GL, Fourth GL, Fifth GL

Machine Language (1GL)

• Language or instructions that can be totally understood by the computer hardware.

• Language that cannot be understood by humans, unless they can read binary.

• It is binary and uses 0s and 1s    eg 1110100010101010101010101001010

• Each section of binary is one instruction for the CPU to act on. This is repeated many times.

• Different machine language for different CPUs

• Can we code directly in machine language? Yes, but not easily.

• Input methods include punch cards, magnetic tape and by toggling switches.

• Yes, this is before keyboards were common for computer use.

Assembler Language (2GL)

• Programs written in assembler language need to be translated into machine language to be understood by the CPU.

• The assembler is the program that translates assembler language to machine code/language.

• Example code has LOAD,  ADD, STORE,   

• Assembler language is specific to hardware.

• Assembler code runs fast. (advantage)

• See example at wikipedia

Procedural Languages (3GL)

• The first type of programming to be portable to many computers.

• Procedural language works by performing a sequence of steps.

• These become the source code which gets compiled into machine language

• This source code gives instructions to do the necessary steps.

• Words and symbols are used 

  • Compute Total Pay

  • If Pay >0

• Procedures can be used for functions that can be called and run to return a value.(chunks of code that can be re-used)

• Example program languages are C / C++, PASCAL and Java and many more.

 Non-Procedural Language (4GL)

• Non-procedural languages specify what a program should do.

• Enables users to access a relational database eg

  • SELECT * FROM Customers

  • WHERE CustomerName = 'Bill';

• These are very good for getting reports from a database eg SQL

• The code is more like natural speech and focuses on input and output

Object Oriented Programming (OOP)

• Programming that uses objects by communicating with other objects.

• This programming uses classes and objects that model objects in the real world.

• The main module is called a class which can have actions or methods.

• Objects can send and receive messages from other objects and also they can process data.

• The code modules can share information that saves time in programming.

• Examples are Java, Visual Basic, Python, Ruby and many more.

Step 5 - Further Research 

1. Video on youtube.com - History of Computing in 90 secs

2. http://www.extremetech.com/computing/91572-the-evolution-of-computer-languages-infographic

3. Comparison of procedural and object-oriented with examples.

4. OOP explained quite well.