APCSP UNIT 3 REVIEW

Fill parent

A property used to make width and height take up the whole width/height of the container.

PaintPot events

Utilized several events including button clicks (to change pen colors), user touch (to make dots) and user drag (to make lines).

Camera component

Located in the Media drawer.

ListPicker

Located in the User Interface drawer.

Accelerometer

Located in the Sensors drawer.

Activity Starter

Located in the Connectivity drawer.

Setter blocks

Used to assign or change the values stored in variables.

Getter blocks

Used to retrieve the values stored in variables.

x and y coordinates

Represent where the user touches in the When Touched event and x1, y1, x2, y2 in the When Dragged event.

Enhancements in Paint Pot

Included changing the background image using the camera, increasing or decreasing the dot size, adding another pen color and adding optional creative features.

Refactoring

Means restructuring a program without changing its behavior, often by moving redundant code into a procedure.

Procedure

Does not return a value.

Function

Does return a value.

Parameters

Abstract variables that procedures can take.

Arguments

Concrete values passed to the procedure from some other block of code.

Comments

Useful for explaining complex code or procedures and can be accessed by right clicking on the block of code.

Global variables

Used to share values between different blocks of code and must be initialized to some default value.

Variable

More abstract than a value because it can represent many different values.

Bug

An error or defect that prevents the app from working the way it is supposed to.

Control logic

Tests to see whether the dot size is 0 or less.

Persistent data

Data that is stored on the device itself which allows the data to be reused (persist) between different uses of an app.

TinyDB

An example of a database that stores persistent data in tag-value pairs.

Tag-value pairs

Only one value may be stored per tag, and if another value is stored, it will replace the original value.

Case sensitivity in tags

Tag names are case sensitive, so 'tag' and 'Tag' would be two separate tag-value pairs.

RLE

Stands for Run Length Encoding and is a method of compression that stores the number of consecutive pixels that are the same color.

Lossless compression

RLE is considered a lossless compression technique because there is no data loss in the process.

Lossy compression

An example is JPEG because pixels are lost in the process, but the human eye can still see the image well enough.

B/W images in RLE

Always starts with the number of pixels that are white, followed by the number of pixels that are black.

Compression for color images

Will decrease the file size, often significantly.

Compression Techniques

Methods used for storing and transmitting data that involve trade-offs.

Compression

A process that reduces the size of files for Internet sharing and storage.

Decompression

The process of restoring compressed files to their original state.

Encryption

A method that limits file readability by unauthorized users, unlike compression.

ASCII

American Standard Code for Information Interchange, a mapping scheme for characters and binary codes.

Binary Strings

Sets of 0s and 1s that can represent numbers, letters, and colors depending on context.

Error Detection

The process of identifying errors in data, which is critical since all data are bits.

Parity

A method of error detection that refers to the evenness or oddness of a number.

Even Parity

A condition where all the 1's in a binary string add up to an even number.

Odd Parity

A condition where all the 1's in a binary string add up to an odd number.

Parity Checking

Involves adding redundancy bits called parity bits or check bits to detect errors.

Parity Bits

Bits added to a binary string for error detection, not part of the actual content.

Magic 8 Ball

An app that responds to the shaking of a device using an accelerometer.

List

A collection of elements of any data type, which can have 0 to n items.

Empty List

A list that contains 0 items.

Index

The position of an item in a list, where the first item is index 1.

Random Selection

The process of selecting random items from a list, which can be assigned to variables.

ActivityStarter

A component used to start any application installed on the device.

Connectivity Drawer

The section in an app development environment where Activity Starters are located.

Redaction

The process of editing a document to remove or obscure sensitive information.

What happens to deleted data?

The data itself remains on the storage device until new data overwrites it. This is why data recovery is often possible using special software, though the success rate decreases the longer it has been since the deletion and the more the device has been used.