Computing Fundamentals (F451 OCR)

Here are 23 pages of extensive notes on the not-so-obvious bits of the OCR F451 syllabus (for the January 2010 exam).

As always, these notes were written for me to revise from, and so there may be bits that are not covered as much as you need to learn them in, or there may be bits that are covered in nauseating detail for you because you are already 100% familiar with them.

Original document is a Word 2007 (.docx) which if you want, email me and I will send you a copy.

These notes cover all six topics within Unit 1:

  1. Components of a Computer System
  2. Software
  3. Data: Its Representation, Structure and Management in Information Systems
  4. Hardware
  5. Data Transmission
  6. Implications of Computer Use
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  • Created by: Jackarias
  • Created on: 29-12-09 21:15
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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Components of a Computer System (3.1.1)
Hardware: physical parts of a computer system
o Three categories: input devices, storage devices and output devices
All systems need instructions of some sort which generally come from the user.
Some systems need text, some high-quality images, and some video images.
Input devices are chosen for their quality and ease of use.
Used so that the computer can be told what to do and what data to use.
Storage devices are used so that the computer can remember what it is meant to do
when it is switched back on after having been turned off, otherwise by the time you
tried to give it a second instruction it would have forgotten the first.
An output device is any hardware used to communicate processed data to
the user.
Used to display what the computer has just done or to control some
device to do something useful.
Software: actual programs or data that a computer system uses (two types...)
o Systems software: set of programs that organise, utilise and control hardware
o Applications software: designed to make use of system for specific purposes
Software (3.1.2)
The systems lifecycle is a set of rules written as a series of stages that need to be
followed in order to produce a new computer system.
It is a term used to describe the stages in an ICT project.
Commonly it is the process by which an existing system is replaced with another.
There are nine stages to the systems development lifecycle:
1. Definition of the problem
2. Feasibility study
3. Collection of information
4. Analysis
5. Design
6. Implementation
7. Evaluation
8. Installation
9. Maintenance
On the next page is an illustration of the systems lifecycle...
Page 1 of 23

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Problem Definition
· Define problem the
system is to
Maintenance overcome
· Problems cleared;
tweaks to improve Feasibility Study
system; data
· Looks at alternative
backed up;
solutions
peripherals
upgraded; relocate
system
Information
Installation Collection
· How to install new · Define how old
system system works and
problems
Evaluation Analysis
· Does the finished · Analyse how
solution meet its current system
requirements? works - uses lots of
· Does it solve…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
The waterfall model is one model of the cycle in which progress is seen as flowing
steadily downwards (like a waterfall) through the phases of:
1. Conception
2. Initiation
3. Analysis
4. Design (Validation)
5. Construction
6. Testing
7. Maintenance
The first formal description of waterfall model is often cited to be from an article
published in 1970 by Winston Royce.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Operating systems (OS)...
o Provide a platform on which applications can run
o Control hardware
o Allow communication with the outside world
:: SIX TYPES OF OPERATING SYSTEM
SINGLE USER ­ one user at a time.
MULTI USER ­ data centrally stored, e.g. supermarket checkout system.
MULTITASKING ­ allows multiple tasks to be run concurrently (or appear to).…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
One of the purposes of the operating system is to provide a human-computer
interface which lets users tell the computer what to do, and allows the computer to
ask the user for input or to display results.
o GUI ­ Graphical User Interface
o WIMP ­ Windows Icons Menus Pointers
MENU BASED ­ often confused with GUI (menus). The whole interface is run from
menus.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
System utilities are programs that perform specific functions (generally
maintenance).
Some tasks that system utilities carry out include...
COMPRESSION FILE CONVERSION KEEPING CONFIGURATION
System utility programs File extensions are related to FILES
convert data into a format specific applications. A These contain information
that takes up far less utilities program enables on system parameters.
memory space.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Some information is stored in computers as numbers in base 16.
This is called hexadecimal (or just hex).
Principles are exactly the same as for denary, binary, octal or any other base.
If you have to be able to count from 0 to fifteen before going back to the
start and putting a 1 in front of the 0 to stand for sixteen it means we have
to have sixteen digits.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Using -75, it goes from 01001011 (in binary) to 11001011 as the first bit changes its
meaning ­ i.e. it no longer stands for "128" but instead "+/-".
This is called sign/magnitude representation because the byte is in two parts:
o The sign and
o The size of the number
There are two PROBLEMS with sign and magnitude:
1. The biggest number that can be represented is now half what it was
2.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
-128 64 32 16 8 4 2 1
0 1 0 0 1 0 1 1 75
0 0 0 0 1 1 1 0 14
0 1 0 1 1 0 0 1 =89
CARRY ==> 1 1 1
The sum here is 1 + 1 and
then a carry is added.…read more

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Computing Fundamentals
OCR F451 Written Exam (January 2010)
:: Jack Bennett, 12F
Designed to include all the symbols that are used throughout the world including all
Arabic, Chinese and Japanese characters.
It is constantly growing in size as more and more characters are accepted.
Data can be collected in a manual way ­ i.e. not directly connected to a computer ­
such as via questionnaires, and then it can be typed into a computer using a
keyboard.…read more

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