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System Software DevelopmentAS Archive
System Software Development
Notes
AS Unit 1 - Introduction To Object Oriented Programming
Software
demonstrate knowledge and understanding of the concepts associated with:
− systems software (management of file types/source/binary/executable/XML);
− application development software (object oriented platforms including open
source);
SYSTEM SOFTWARE
A system is a set of interacting or interdependent components forming an
integrated whole. The physical components or hardware of a computer do all the
hard work, and when connected as a system they provide the platform
necessary to perform functions and outputs of a device.
The CPU - or central processing unit, is responsible for processing all of the
instructions asked of it by the other hardware components and software, by
System Software Development AS Archive 1
, sequencing all logical inputs and outputs and performing thousands of
calculations every second.
Software is the brain of the computer as it takes user input and tells the
hardware what functions to perform. System Software is the most fundamental,
with examples including:
The BIOS (basic input/basic output) - manages the data flow between the
hardware and the processor.
The Boot - loads the Operating System into the hard drive or RAM.
The Assembler - arranges the data into bits which is the format the processor
can work with.
Device Drivers - Manage the input and output of all the devices attached to
the computer.
The Operating System - The Nucleus of all software activity. Without it, you
cannot communicate with the computer’s hardware and it is the first program
loaded into memory when the computer is booted. The operating system
relays instructions to the processor which computes the command. The OS
is responsible for translation into machine code. The most common are
Windows, Mac OS X and UNIX.
On top of the system software is Application Software, higher level software
which provides users with functionality such as word processing, browsers and
databases.
BINARY AND CODE
The CPU only understands Machine Code. This is in binary.
A Byte is a unit of digital information that is made up of a set of bits, most
commonly a byte is 8 bits, for example 11000101. An octet can have any value
between 0 and 255, because each bit in a byte represents 128|64|32|16|8|4|2|1 .
ASCII, or the American Standard Code for Information Interchange, is a standard
to represent the characters on a keyboard. in total, ASCII uses 7-bit and has a
maximum of 128 characters. It is still transferred, however, using 8 bits, for
example the character key 4 might have a decimal value of 52 and a binary
value of 00110100.
However 128 was not enough characters for languages like Japanese, so
Unicode, which uses 16 bits (2 bytes) was introduced, allowing 512 characters.
System Software Development AS Archive 2
, A high level programming language can can be defined as readable and
understandable representation of instructions we are requiring the computer to
perform. This makes development more manageable.
The code written by the programmer is the source code. The compiled and
translated code is called machine code. Source code is ultimately stored in text
files meaning source code can be written in notepad++, but major languages
have purpose built Integrated Development Environments, or IDEs.
IDE AND FILE TYPES
An IDE is an application to aid a developer writing code and acts as a text editor,
debugger and compiler. Some functionalities include:
Code Completion and Code Insight - suggestions to complete statements
and highlight errors
File Resource Management - Builds the folder structures to hold files on the
hard drive in an organised manner.
Debugging - Provides the ability to look into the code while the application is
running to investigate the values being created or calculated.
Compile and Build - Compiles the high level language to machine code and
builds the application.
Open Source IDEs are free to download and free to use, but the catch is, they
are constantly in development by the users themselves, and are sometimes quite
buggy. Without an IDE, developing would be extremely cumbersome.
When a dev has written code and is ready to release, they need to do so without
any access to the source code. This is fundamental to any retail software
program. This means an executable file is necessary, or more commonly, .exe.
An exe is a read only file composed of machine code that runs when opened.
Software apps are centered around the creation, manipulation and distribution of
data. It can have direct access to its own data via a databse or it can send and
recieve data to other applications to be utilised. One of the most prevalent forms
of this data transfer is XML, or Extensible Markup Language. It is accepted in all
forms of development. It follows a similar format to HTML, and is human
readable and easy to follow. The basic building block is an element, defined by
tags, having a beginning and an ending tag, for example;
<school>
<subject>
<name> Software Systems Development </name>
System Software Development AS Archive 3
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