computing all

abstraction

picking out the important parts from a problem and ignoring the rest.

decomposition

breaking down a problem into smaller problems that can be solved separately.

algorithm

a set of step by step instructions that can be followed to solve a problem.

pseudo-code

writing an algorithm in the style of a programming language but using plain english.

one advantages of presenting an algorithm in pseudo-code.

It is easier to write as there is no specific syntax to follow.

another advantage of presenting an algorithm in pseudo code.

It can be read without knowledge of any specific programming language.

why might someone use a flowchart instead of pseudo-code to write an algorithm.

it is presented visually, making it easier to follow.

flowchart symbol for process

rectangle

flowchart symbol for decision

diamond (always 2 outputs - yes or no)

flowchart symbol for subroutine

flowchart symbol for input/output

parallelogram

boolean

a value that can take only one of two values

(e.g true/false)

integer

a whole number (e.g 9)

character

any letter, digit or symbol (e.g g, {, 7)

double

A number that has a decimal point (e.g 1.5)

variable

a named value that a program can remember and change.

constant

it's value can't be changed whilst the program is running.

string

a data type for text

string concatenation

it joins strings to form a longer string

sequence flowchart

only one path from start to stop

selection flowchart

multiple branching paths from start to stop

iteration

a statement that makes any code inside it repeat a number of times.

examples of a condition-controlled loop

while, do-while, repeat-until

Nested Iteration

a loop inside another loop

why is it better to use a for loop than copy out code multiple times

it makes the program easier to read.

an array

a data structure that can store multiple data values under one name

2d array

an array where each element is another array.

subroutine

a set of instructions stored under one name that can be called at any time in the program.

local variable

a variable that is defined within a subroutine and only exists when the subroutine is running.

low-level language examples

Machine code and assembly language

low level languages

Programming languages that a computer can (more directly) understand.

high level languages

programming languages whose instructions closely resemble the English language

high level languages examples

python, C++, PHP

why are high level languages more popular

easier for people to read and write

why might someone use a low-level language

the code could execute faster.

assembler

translates assembly language into machine code

NOT logic gate and truth table

01

OR logic gate and truth table

0111

AND logic gate and truth table

0001

XOR logic gate

0110

letters used as hexadecimal digits

A, B, C, D, E, F

why would programmers use hexadecimal instead of binary

numbers in hexadecimal are a lot shorter, making it easier to remember.

character set

a collection of characters that a computer recognises from it's binary representation.

which character set is larger unicode or ASCII

unicode

colour depth

number of bits used for each pixel

file size equation

file size = image resolution x colour depth

sample resolution

number of bits available for each sample

how does increasing the sampling rate improve the sound quality

higher sampling rate means samples are taken more often, so less data is lost.

file compression

reduces the size of the file

Losless Compression

reduces the fie without losing data

lossy compression

reduces the file but data is lost

cpu

central processing unit

what is found in the cpu

control unit

what is held in cache memory

control unit

what is the purpose of the cpu

it processes the data and instructions that make the systems work.

what is the ALU

Arithmetic Logic Unit

what does the alu do

Performs arithmetic and logic operations.

what does the control unit do

fetch, decode and execute, and controls the flow of data.

what are cpu busses

collections of wires used to transmit data between components of the cpu.

what are registers in cpu

to hold data, instructions and memory

how does the clock work in the cpu

it sends out a signal that cycles between 1 and 0. It synchronises when instructions should be carried out.

RAM

Random Access Memory

is ram volatile or non volatile

volatile meaning it loses its data when the power is off.

ROM

read only memory

is rom volatile or non volatile

non-volatile

what is a flash memory

non-volatile memory that stores data in electrical circuits by trapping electrons.

secondary storage examples

Solid state drive, CD and USB pen drive

what is secondary storage

non-volatile memory

examples of operating systems

android, iOS, windows

what do utilty software do

help you look after your computer

internet

group of inter-connected networks.

World wide web

one service that makes use of the internet.

local area networks

a network owned by one organization.

how can the www be accessed

web browsers such as chrome, safari or firefox

LAN

Local Area Network

what is a lan

a network owned by one organization

WAN

wide area network

what is a wan

a network that is spread over a wide geographical area.

what does a wan use to connect 2 remote locations

satellites, telephones or radio waves.

IP address

A number assigned to any item that is connected to the Internet.

IPV4

4 bytes of data

IPV6

6 bytes of data

bytes in 1 data packet

512

packet switching

each packet will contain the same number of bytes. The packets might flow to the internet via different routes.

points in a network diagram

nodes

what is a router

any node that can route packets from one place to another.

NIC

network interface card

what is nic

built into every single device. You need this in order to connect to the internet.

router

looks at the destination of packets and sends them to the network that is closer to the destination.

switch

connects each node in a network. When a packet of data arrives, they can sent it to the correct computer.

protocols

a set of instructions to follow.

wireless network advantages

no need to lay cables, easy to connect devices

wireless network disadvantages

can be less reliable and secure

Topologies

a way in which parts of a system are connected

topology examples

star and bus

star top ads

fast data transfer to hubs.

star top dis

if central switch fails, the whole network goes down.

bus top ads

less cable so cheaper to install network.

bus top dis

any device can view all data on cable, creating a security risk.