Loops and Stuff

3 types of Loop

Nested Loop - loop inside other loops
Conditional Loop - will loop until a specified condition is met
Fixed Loop - loops a set number of times every time

Macro
we can record a set of instructions and get them to repeat by pressing a key stroke (or shortcut which we assign it)

Pre-Defined Functions

int() round() rnd()
commands in programming language, they are already written and we can use them

Compter Languages

Machine Code - the language that computers understand, represented as binary (1,0) and as an electrical charge in the computer system

We program in HLL High Level Languages
+ Must be translated before execution
+ English like language
+ They are portable

LLL - Low Level Languages
- understood by the components and the processor etc etc etc

Translators

+ Compiler - translates and executes each line of code at the same time
+ runs faster, because it gives you an executable file once there are no errors
- not good for debugging, gives you all your errors at once
+ Interpreter - translates and executes each line of code one at a time
+ stop when it finds an error, easier to debug
- slower, must run and translate every time, Interpreter is always running during interpretation

From I onwards

I - Implementation

+ choose which language to write the program in (Visual Basic etc)
+ We simply enter in programming language to a Text Editor

T - Testing
Examples do while age < 0 or age > 100
+ Normal - a test within the boundaries of expected input - 50, 60, 44, 98
+ Extreme - testing on the boundaries of expected input - 0, 100
+ Exceptional - test outwith the boundaries of expected input - 111, "Lion", -1

= Fully Testing is where you carry out tests using each of the three types of test

D - Documentation

+ User Guide - contains how to use the program (after its been installed), controls etc
+ Technical Guide - specifications of the program (requirements) e.g. Minimum Memory Requirements, Minimum Processor Speed, Compatible Operating Systems

E- Evaluation


+ Readability - how easy the program is to read and understand for other programmers

!!!! - Ways to improve readability

- indentation, blank lines, comments, good variable names

+ Fitness for Purpose - Does it do what its supposed to do! (Software Spec.)

+ User Interface - user friendly, easy to use

M - Maintenance

+ Perfective - program does what its supposed to do, but we add new features that weren't in Software Specification
+ Corrective - fix any errors that are not found during testing
+ Adaptive - change the program for different platforms (different processors, OS, Hardware)

Dancing!

The Software Development Process is an Iterative Process


We can remember the stages in the correct order by remembering
A Dance In The Dark Every Monday

The first stage is the Analysis

The document produced at this stage is called Software Specification

This document is a legally binding contract stating what the Software MUST do

The second stage is the Design stage

There are 3 different approaches to this Pseudocode, Structure Diagram and Flow Diagram

The two of these which are Graphical Design Notations are Structure and Flow Diagrams

Computer Software

Operating Systems
most important program on the computer system
Starts when the computer is turned on running constantly until it is turned off (the computer)
Jobs of the OS
+ Controls the Input and Output Devices
+ Reports Errors
+ Controls Security
+ Provides the Human Computer Interface (HCI)
+ Controls where items are stored in memory
+ Schedules tasks (virus scans, updates etc)

* OS that we know. Windows 95, 2000, XP, Vista, 7, 98 ME, Linux, Apple Tiger, Apple OS X

Application Programs
perform specific tasks - Word Processing, Presentation, Spreadsheets, Graphics, Desktop Publishing

Saving in Standard File Formats
so that programs or documents saved on one computer system or application program will open in another different application program

Standard File Formats for Graphics
JPEG, GIF, BMP,

Standard File Formats for Text
TXT, RTF (Rich Text Format) ASCII
RTF stores some formatting information

Objects and Operations

Objects - Text, Graphics, Graphs, Cells, Rows, Columns, File, Records, Fields, Circle, Square, Line,

Operations - Copy, Paste, Cut, Insert, Crop, Rotate, Scale

Viruses
- infects your computer and makes it perform involuntary tasks - destructive piece of code

*Symptoms*
Slow your computer down
Applications dont work properly
Takes up processor
Recieve uncommon error messages
Computer Crashes (reboots unexpectedly)

*Causes of Infection*
Dodgy websites (gaming)
CDs from friends
Email - attachments
Peer to peer downloads - ShareZa, LimeWire

*Protect Yourself*
Anti Virus Software
Anti Malware
Anti Spyware
Firewalls
and running these often

Client Server Network

Some Examples of Servers are ...

File Server, Print Server, Web Server

A Client Server Network is ...

A network in which client machines access and make use of the resources available on the different servers.


Acts

Data Protection Act
Data Users
- people who access the info for you (Bank Teller)
Data Subject
- Person who the information is about
+ the right to have their info changed
+ the right to view information for a fee. Not always allowed to see it (Matters of National Security)
+ right to compensation if the act is broken
Data Controller
- the company that holds the information
+ must take measure to protect info (passwords, levels of access etc)
+ make sure its accurate and up to date
+ only keep it for as long as necessary
+ not sell the Data on or transfer outside the EU
Information Commisioner
- must register with them if you wish to store personal info!

Copyright, Designs and Patents Act
+ downloading music, videos, films etc without permission
Computer Misuse Act
+ Hacking
+ Spreading Viruses

Networking

What is a Network
a series of computers linked together so that they can communicate, share peripherals, share data etc

Stand Alone Computers aren't on networks


LAN

Local Area Network

covers a smaller geographical area ( building, school etc)

Transmission Media
+ copper wire
+ fibre optic
+ wireless


WAN

Wide Area Network

Covers a larger geographical area (like a country, city)

Trasmission Media
+ satellite
+ optical fibre
+ microwave

Functions of Interfaces!

Buffy Does Crack!!

Buffering! - temporary storage of Data


D (DtoA!, AtoD!) - Data Conversion
Digital to Analogue, Analogue to Digital

C - Compensating for differences in speed of processor and peripherals!

Different features of Comparison

PPM (Pages Per Minute) Speed, DPI (Dots Per Inch, Resolution, Print Quality) Price, Speed of Data Transfer, Clock Speed

Inkjet V Laser
Laser are generally faster (higher PPM)
Inkjet usually better quality prints
Inkjet sprays ink onto page, Laser uses toner and an actual laser!
Inkjet is noiser! Laser prints come out warm because of heater to dry the toner!

Backing Storage Devices in size order
Floppy Disk
CD-ROM
Flash Drive
USB Pen Drive
DVD-ROM
Magnetic Tape
Hard Drive

Monitor Types
CRT - Cathode Ray Tube
LCD - :Liquid Crystal Display
TFT - Thin Film Transistor

Types of Access

Sequential

Must go through the memory locations in order to get to the one required



Direct/Random

Can access at any point (can skip directly to ANY memory location required)

5 box diagram

The Processor

C U A Love U Right!

CU - Control Unit
makes sure instructions are carried out in the right order

ALU - Arithmetic Logic Unit
carries out all calculations and makes logical decisions

R - Registers
temporary memory locations

Main Memory
RAM - Random Access Memory - TEMPORARY
ROM - Read Only Memory - PERMANENT

Input Devices
mouse, keyboard, mic, camera, webcam, scanner

Output Devices
monitor, speakers, printer, projector,

Backing Storage
USB Pen, Hard Disk, Floppy Disk, CDr,rw,rom, DVDr,rw,rom External Hard drives, Memory Cards

Tidy Up!

UNICODE - 16 bit, capable of storing more characters allows it to store more languages



Advantages and Disadvantages of Binary

+ Easier to store the two states on backing storage
- its harder to write programs in Binary (longer, difficult to spot mistakes)
+ not affected by voltage degredation
+ fewer rules of addition to code into the processor (0 + 0, 0 + 1, 1 + 0, 1 + 1)

Calculation of Graphics Sizes

How do we do it!?


= length in pixels * height in pixels

= (length * dpi) * (height * dpi) dpi = resolution


DPI = Dots per inch

Bitmaps

How are graphics stored in a computer system - bitmap!

stores the (0,1) colour of every individual pixel

Resolution (High res has more pixels)

We measure resolution - Dots Per Inch (DPI)

Binary

Sizes

Bit
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte

Bit and get it to Megabyte
/8 = byte /1024 = kilobyte /1024 = megabyte

Terabyte to kilobyte
Terabyte * 1024 = gigabyte * 1024 = Megabyte * 1024 = Kilobyte

ASCII Code and FPR!

ASCII stands for?

American Standard Code for Information Interchange


How many bit code is it?

7, extended ASCII uses 8

How many characters can it represent?

128

What is the Character Set?

All the characters that can be represented (text, numbers, punctuation, includes control characters)

What are the control Characters?

Space, Tab, Enter ... Non Printable Characters that change the format of display

Floating Point Representation is used to represent Real Numbers.

How do Computers use Floating Point to represent Real Numbers?


By using a MANTISSA and an EXPONENT - Mantissa represents the actual number. Exponent tells us how many places to move or "float" the decimal point!

Binary Numbering System

The Binary Numbering System is a two state numbering system using 0 and 1 as its two states

The Computer System is a two state machine using ON and OFF as its two states.

The ON and OFF states can be represented by the 1 and 0