Download Classification of Program Languages

Classification of programming languages
Learning Objectives
• Learn how programming can be performed in
machine code, assembly language and high level
languages
• Learn that there are different methods of
programming known as a paradigms
• Learn how interpreters and compilers are used to
turn programming code in to machine code (0s and
1s)
• Learn what bytecode is.
Classification of programming languages
Programming
Languages
Machine
Code
Assembly
Code
Imperative
High Level
Languages
Object
orientated
Declarative
Functional
Classification of programming languages
Machine Code
• Computers originated in the early 40s and initially to aid the
war effort.
• Initially to programming them you had to speak the languge
of computers which is 0s and 1s. This was either done by a
series of switches or with special punch cards that were fed
into the computer.
• These 0s or 1s or binary was the machine code of the
computer. The only language it really understands
• Separated into two parts – The Opcode and the Operand.
OPCODE
OPERAND
What to do
What to do it on.
Classification of programming languages
Machine Code
• Computers would use an instruction set to determine what
the 0s and 1s meant.
• TASK
Work through Machine Code worksheet
Classification of programming languages
Assembly Language
• Programming in machine code was very time consuming and
very difficult to debug
• The need to make programs more user friendly led to the
development of Assembly language
• The 0s and 1s used in the opcode was replaced with
mnemonics
• Look at the example given in the LMC
• Can you create a multiplication program in the LMC
Classification of programming languages
Assembly Language
•
The assembly code still needs to be converted to machine code so an
assembler is used to translate it into object code (Machine code)
•
Advantages of Assembler over high level languages
• Programs are executed quickly as a complier does not optimise
the machine code that it produces as effectively as a
programmer who codes in an assembly language that maps
directly to machine code.
• Program code is relatively compact for the same reason
• Assembly language allows direct manipulation of the registers
on the processor, giving high levels of control.
• Used in embedded systems with low memory and processing
power.
• Real time applications that require quick reponse times to
inputs might also use assembly
• Device drivers will also use assembly for more control over
access to hardware
Classification of programming languages
High Level Languages
•
•
•
Increasing complex demands on computers lead to the development
of high level languages to help programmers.
High level languages are problem orientated rather than machine
orientated (low level languages)
• What the program will have to do rather than the components of
the computer it will be used with.
• Allows programs written with HLL to be portable.
Different languages are suitable for different types of problems, e.g.
scientific, mathematic, visual.
• Classified into three groups
• Imperative
• Object orientated
• Declarative
Classification of programming languages
High Level Languages
•
Imperative
• Procedral languages
• Work by typing list of instructions
• Uses subroutines and procedures
•
Object orientated
• Works by creating objects where the intructions required to run
the program are contained within the object. Objects are
grouped together or derived from classes.
•
Declarative
• Use a set of facts and rules to declare an outcome rather than a
process. A form of logical programming – used in artificial
intelligent systems.
Classification of programming languages
High Level Languages
•
Main characteristics of high level languages
•
•
•
•
•
Easier to program as more like a natural language
Need to be translated like assembly language
One command in a high level language may consist of a great
number of machine code instructions.
They are portable.
Use a wide variety of programming structures to help maintain
and code applications.
Classification of programming languages
High Level Languages
•
Translating high-level languages
•
Interpreter
• Reads a line and actions it straight away.
• Can inefficient when dealing with iterative statements
• With an IF statement the condition is interpreted first and
the rest is interpreted only if the condition is true.
Classification of programming languages
High Level Languages
•
Interpreter
•
Benefits
• You do not need to compile the whole program in order to run
sections of code. You can execute the code one statement at a
time.
• As the code is translated each time it is executed, program code
can be run on processors with different instruction sets
• Because of this, an interpreter is most likely to be used whilst a
program is being developed.
Classification of programming languages
High Level Languages
•
Interpreter
•
Drawbacks
• No matter how many times a section of code is revisited in a
program it will need translating every time. This means that the
overall time needed to execute a program can be very long.
• The source code can only be translated and therefore executed
on a computer that has the same interpreter installed.
• The source code must be distributed to users, whereas with a
compiled program, only the executable code is needed.
Classification of programming languages
High Level Languages
•
Compiler
Converts the whole source code into object code before the program
can be executed.
Object code can then be executed everytime. Execution will be quick
Benefits
Once compiled – no longer need the source code.
Very difficult to reverse engineer.
Drawbacks
Can take a while to set up for debugging.
Object code can only run on a computer that has the same platform
Classification of programming languages
High Level Languages
•
Bytecode
This is the process whereby code is compiled to be platform
independent.