Programming concepts
Professional programmers use specialised skills and creativity to write
programs. Some people find programming easy and fun.
The programming concept
you need to understand are described below.
Application software package
This is the end result of programming. When an application is running,
the user interface is what you see and interact with by typing or using
buttons. Applications software packages are created by programming with a
high-level programming language and are used to solve problems and to
entertain.
High-level programming language
A high-level programming language is one that is quite close to natural
human language (rather then computer language, aka machine code). This is what
most programmers use to write programs.
Examples of high-level programming
language are C# (pronounced ‘C Sharp’), C++, Java, and Visual Basic.
Microsoft Office applications, including excel also offer high-level
programming functionality using VBA (virtual basic for applications). This
allows users to add automation to office documentsby creating macros.
For
example, a user might program an excel macro to go through data, hiding rows
that are not wanted making visible rows that are.
High-level programming languages are compiled into machine code so that
the computer can understand and run it.
Low-level programming language
These languages are close to machine code, and therefore need less
changes before a processor can actually run them (compared to high-level
programming language). Low-Level programs are written using an assembler, which
is simply a programming environment designed to help write these programs.
Each simple command you type into the program you are writing gets
assembled into the equivalent machine code instruction. This is different from
high-level language where a single line could compile hundreds of lines of
machine codes that the processor will run to action that line of the code.
Machine Code
This is the actual binary code that the CPU can understand. Before any
program you write can run on a computer, it must be translated (compiled or
assembled) into machine code.
Hardware
The hardware is controlled by software as the CPU decodes each machine
code instruction to carry out actions such as adding two numbers together,
displaying part of the user interface on the screens or loading a document into
RAM from the disk.
Characteristics of high-level programming language
High-level programming languages are powerful and easy to understand.
Programs written in a high-level language are much closer to spoken
language then low-level, as well as being a lot more intuitive to use.
High-level programming languages have several ways of working,
including:
-
Imperative code – this is used in most languages,
both older and modern. In this type of code each program statement is a step
towards handling the inputs processing and outputs.
-
Procedural programs – These have definite start and
end points. These language were normal before GUI operating systems, as usually
have a single starting point then follow as a sequence. Modern programs respond
to events so can have many start points within the code.
-
Event-Driven programs – these respond to events
such as a mouse click. These are the current approach for modern programming
because they need to produce responses to the great variety of events that GUI
operating systems provide.
-
Object-orientated programs (OOP) – These view
programs as a collection of objects. Such as a database record, and not as a
list of tasks in a procedural programming. Each object can be viewed as an
independent ‘machine’ within a distinct role or responsibility , which is
capable of receiving messages, processing data, or sending messages to other
objects.
Characteristics of low-level programming language
Assembly language is written using an assembler, which helps the
programmer by checking for errors in the mnemonics before compiling the program
into machine code.
Machine code is binary bytes so could be written without an assembler by
typing binary numbers direct into memory. However, this would be very difficult
as the programmer would only see the program as numbers. The mnemonic abbreviations
in assembly languages make understanding the program much easier.
Flow charts
You can use flow chart to help design a program.
A flow chart is a
diagram that shows how a program works and the routes can be taken through it.
A flow chat shows where the program starts and where decisions are
taken. Processing operations, inputs, and outputs.
Process – Used to represent a calculation or general processing
operation carried out by the program.
Terminator – Shows where the program starts or finishes.
Decision box – used in any place where the program makes a test to
decide on a choice of directions to run the next code.
Data (input/output) – Represents any part of the program that takes data
in or shows prints or outputs data.
Connector – aka flow line. These lines connect other parts of the flow
chat to show the routes the program can take. Flow lines usually have an arrow
at one end to the show the direction the program takes. If there is no arrow
the direction will be either downwards or to the right.
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