Computer Science Flashcards

Flowcharts

• Flowcharts use different boxes for different commands.
• Arrows connect boxes and show the direction to follow.
• Some boxes might have multiple arrows coming in or going out.
• The three main features used in programs are sequence, selection, and iteration.

Boxes Used in Flowcharts

• Start/Stop: The beginning and the end of the algorithm are put in boxes with rounded corners; they're sometimes called terminals.
• Inputs/Outputs: Anything that's put into or taken out of the algorithm goes in a parallelogram box.
• Processes: General instructions, processes, and calculations go in rectangular boxes.
• Decisions: Decisions, often a 'yes' or 'no' question, are put in diamond boxes.
• Sub Programs: Sub Program reference other flowcharts.

Sequence

• Sequence is where each instruction is carried out in order, one after another.
• There is only one route to follow—no decisions or repeats.

Selection

• Selection is where decisions are made that affect which instructions are carried out next.
• They are represented in flow diagrams by diamond boxes.

Iteration

• Iteration is where a certain set of instructions is repeated.
• The number of times that the instructions are repeated can be fixed or can depend on a condition.
• Iteration can be spotted in flow diagrams when an arrow points back to a previous instruction or decision.

Understanding Computers

• Computers require input hardware, processing hardware, and output hardware.
• The hardware that defines a computer is the CPU and memory; without these, a computer could not function.
• The CPU and memory work together to run programs.

CPU

• CPU executes programs using the fetch-decode-execute cycle.

Memory

• Memory stores program operations and data while a program is being executed.
• There are several types of memory, including registers, cache, RAM, and virtual memory.

Storage

• Storage stores programs and files long term, even when they are not in use.
• Devices such as hard drives, USB memory sticks, or SD cards are used to store files such as photos, music, and software applications long-term.

Input Devices

• An input device is any piece of computer hardware used to provide data to a computer system.
• Examples include keyboards, mice, scanners, digital cameras, and webcams.

Output Devices

• An output device is any piece of computer hardware used to communicate the results of data that has been processed.

Central Processing Unit (CPU)

• The Central Processing Unit or CPU is arguably the most important component of a computer.
• The CPU can be thought of as the brain in a human.
• It is responsible for all of a computer's processing.

Fetch-Decode-Execute Cycle

• The CPU operates by repeating three operations:
  • FETCH: Causes the next instruction and any data involved to be fetched from main memory.
  • DECODE: Decodes the instruction to make sure it can be carried out.
  • EXECUTE: Carries out the instruction.

Key Vocabulary

• Clock Speed: The speed of a computer CPU, measured in hertz (GHz).
• CPU (Central Processing Unit): The brains of the computer that processes program instructions; also called a microprocessor.
• GHz (Gigahertz): One billion hertz per second. This is a measure of frequency and is used to describe bus speeds and CPU clock speeds.
• Hardware: The physical parts of a computer system, e.g., a graphics card, hard disk drive, and CD drive.
• Software: The programs that run on a computer.
• ROM (Read Only Memory): A small program held in ROM called the bootstrap loader is automatically executed on start-up of the computer.
• RAM: Memory that is constantly being written to and read from. It does not retain its contents without a constant supply of power, i.e., when a computer is turned off, everything stored in its RAM is lost.

Binary Numbers

• Computers use binary numbers, 0 and 1.
• This is because computers use switches, and a switch can only be ON or OFF.
• The Binary number system is referred to as Base 2 because it uses 2 numbers, 1 and 0.
• Binary is the language understood by the computer.
• All computer programs must be translated into binary code for the computer to understand and carry out instructions.

Denary Numbers

• The Denary number system is referred to as Base 10.
• The numbers 0-9 are used to represent powers of 10 (1, 10, and 100, 1,000 and so on).
• Denary is the language understood by humans.

Example

• Denary number 172 is represented as 10101100 in binary
• There is a 1 in the 128, 32, 8 and 4 columns so add these together to find the denary number.

128+32+8+4=172

Adding Binary Rules

• 0+0=0
• 1+0=1
• 1+1=0 carry 1
• 1+1+1=1 carry 1

Binary Units

Modelling Data

• Spreadsheets - A program that can display and process data (including numbers and text) in a structured way.
• Rows and Columns - Divide each table up into individual cells.
• Cells - Each cell in a table can be identified using the column letter and row number as coordinates.
• Formulas - An instruction to the computer to process data held in specific cells. It always starts with the = sign.

Functions:

• SUM - Adds up numbers in a cell range

• MAX - Finds the largest value in a cell range

• MIN - Finds the smallest value in a cell range

• AVERAGE - Finds the mean of numbers in a cell range

• IF - Checks if data matches a condition, the result depends on the match being true or false.

• VLOOKUP - Displays data from a table in another part of the spreadsheet

• Charts - Displays data in a visual way, these include Bar Graphs, Line Graphs, Scatter Graphs and Pie Charts

• Sort - Arranges the data into a more suitable order eg. Highest to lowest, alphabetically

• Filter - Shows only the data that the user has specified.

• Conditional Formatting -The format of a cell is automatically changed if its contents meet certain conditions.

  ### National Curriculum Links

• I can design, use and evaluate computational abstractions that model the state and behaviour of real-world problems and
  physical systems

• I can undertake creative projects that involve selecting, using and combining multiple applications to achieve challenging goals,
  including collecting and analysing data and meeting the needs of known users.

Using Media

• Software application - a computer program designed to carry out a specific task
• Word processor - Allows you to type letters/symbols electronically and save, print or edit them.
• Formatting-Changing the appearance and layout of a document
• Plagiarism - The process of practice of using another person's ideas or work and pretending it's your own
• Copyright Law - Using digital images without permission from the owner
• Paraphrase-To repeat something written or spoken using different words
• Citation - Referencing someone else's work
• Credibility of a source - Checking the author and the source making sure it is reliable
• Adaptions - Making changes and modifications
• Commercial Use - Making money from the product

Impact of Technology

• Computing - The study of algorithmic processes and development of both hardware and software
• Secure Password - A password that is designed to be difficult for a person or program to guess
• Hazards - Anything that poses a threat to a computer's security, performance or functionality
• Email - The exchange of messages from one user to one or more recipients via the Internet
• Recipient - A person that receives something eg. Email
• Collaborating Online - Using the Internet and online tools to work together from various locations
• Online Community - A group of people who belong to a particular group on the Internet
• Presentations - An activity in which someone shows, describes or explains something to a group of people
• Audience - A group of people who are spectators to an event such as a play, concert or meeting
• Cyberbullying-Sending, posting or sharing negative, harmful, false or mean content about someone else
• Catfishing-Someone sets up a fake online profile to trick people on a social networking service