APCSP EXAM

Syntax Error

A mistake in typed code that violates the rules of the programming language. Typically, code with syntax errors will not run.

Logic Error

A mistake in an algorithm or program that causes it to behave unexpectedly or return the incorrect value.

Run-time error

A mistake in a program that happens only when the program is actually run, such as a program attempting to access memory that does not exist.

Overflow error

Error that results when the number of bits is not enough to represent the number (like a car's odometer "rolling over").

Bit

A binary digit, either 0 or 1.

byte

A sequence of 8 bits

roundoff

Error that results when the number of bits is not enough to represent the number with full precision (like using 3 digits to represent pi as 3.14).

analog data

Values that change smoothly, rather than in discrete intervals, over time. For example, the pitch and volume of a live concert.

lossless data

Compressing data in a way that preserves all data away and allows full recovery of the original.

Lossy

Compressing data in a way that discards some data and makes it impossible to recover the original.

Metadata

Data about data, like descriptive information about a file or a row in a database.

sequencing

The sequential execution of steps in an algorithm or code in a program (like steps in a recipe).

Selection

A Boolean condition to determine which of two paths are taken in an algorithm or program.

Iteration

The repetition of steps in an algorithm or program for a certain amount of times or until a certain condition is met.

Linear Search

An algorithm that iterates through each item in a list until it finds the target value.

Binary Search

An algorithm that searches a sorted list for a value by repeatedly splitting the list in half.

Reasonable run time

A run time for an algorithm that doesn't increase faster than a polynomial function of the input size (like \[10n\], \[n^2\], etc). An unreasonable run time would increase superpolynomially (like \[2^n\] or \[n!\]).

Heuristic

A technique that helps an algorithm find a good solution in a hard problem (like always walking toward the north star when you are stuck in a forest).

undecidable problem

A problem that is so logically difficult, we can't ever create an algorithm that would be able to answer "yes or "no" for all inputs (like the halting problem).

Library

A collection of procedures that are useful in creating programs.

API

Application Programming Interface, a library of procedures and a description of how to call each procedure.

Modularity

The separation of a program into independent modules that are each responsible for one aspect of the program's functionality.

Traversal

The iteration over the items in a list. A full traversal iterates over every item, while a partial traversal iterates over a subset of the items.

Computing Device

A physical device that can run a program, such as a computer, smart phone, or smart sensor.

Computer Network

A group of interconnected computing devices capable of sending or receiving data

Bandwidth

The maximum amount of data that can be sent in a fixed period of time over a network connection, typically measured in bits per second.

Protocol

An agreed upon set of rules that specify the behavior of a system.

Scalibility

The ability of a system to adjust in scale to meet new demands.

IP Protocol

The protocol that determines how to address nodes on the network (with IP addresses) and how to route data from one node to a destination node (using routers).

TCP (Transmission Control Protocol)

A data transport protocol that includes mechanisms for reliably transmitting packets to a destination.

UDP

A lightweight data transport protocol with minimal error checking.

World Wide Web

A system of linked pages, media, and files, browsable over HTTP.

HTTP

The protocol that powers the Web, used to request webpages from servers and submit form data to servers.

parallel computing

A computational model which splits a program into multiple tasks, some of which can be executed simultaneously.

Speedup

The improvement in the amount of time a parallelized program takes to solve a problem, computed as the amount of time to complete the task sequentially divided by the amount of time to complete the task when run in parallel.

Distributed computing

A computational model which uses multiple devices to run different parts of a program.

Digital Divide

The idea that some communities or populations have less access to computing than others, typically due to limitations of Internet speed or computer hardware access.

Crowd Sourcing

A model in which many online users combine efforts to help fund projects, generate ideas, or create goods or services (like Wikipedia).

Citizen Science

Crowdsourcing for science! The participation of volunteers from the public in a scientific research project (like collecting rain samples or counting butterflies).

Creative Commons

An alternative to copyright that allows people to declare how they want their artistic creations to be shared, remixed, used in noncommercial contexts, and how the policy should propagate with remixed versions

Open Access

A policy that allows people to have access to documents (like research papers) for reading or data (like government datasets) for analysis.

PII

Information about an individual that can be used to uniquely identify them (directly or indirectly).

Multifactor Authentication

A method of user authentication which requires the user to present multiple pieces of evidence in multiple categories (such as knowledge and possession).

encryption

The process of scrambling data to prevent unauthorized access.

Symmetric encryption

A technique for encrypting data where the same key is used to both encrypt and decrypt data.

Public Key Encryption

An asymmetric encryption technique that uses different keys for encrypting versus decrypting data.

cookie

A small amount of text that tracks information about a user visiting a website.

Virus

A type of computer malware that can make copies of itself.

Phishing

An attack where a user is tricked into revealing private information, often via a deceptive email.

Rogue access point

A wireless access point that provides an attacker with unauthorized access to the traffic going over the network

digital certificate

a data file that identifies individuals or organizations online and is comparable to a digital signature

for (var i = 0; i < n; i++)

repeat this loop n times

for (var i = 0; i < list.length; i++)

for each item in list

Tradeoff

something negative that happens in exchange for something positive

What is a bit?

A binary digit, a 0 or a 1.

what is a byte

a group of 8 bits

01100011 is a...

byte

a bit can only represent:

one of 2 possible values

A sequence of three bits can represent:

8 possible values (2^3)

How many different values can four bits represent?

16

Binary digit

0 or 1

why do computers use Bytes

a computer prefers to process 8 bits at a time. The byte is also the smallest addressable unit of memory in most modern computers.

How many bits are in 4 bytes?

32

how do you know if a binary number is odd

if it has a 1 at the end

the highest number that can be represented by \[n\] bits

2^n - 1

how to find the least number of bits that can represent n

count the number of zeros and ones to see how many bits are used

there are 3 yes or no options. what is the minimum number of bits that can be used to represent the options

3

Why might programs sometimes encounter issues with roundoff, overflow, or precision of numeric variables

due to limited computer memory

Consider a computer that uses 6 bits to represent integers: 1 bit for the sign and 5 bits for the actual number. What's the largest positive integer it can represent?

31

Floating Point Representation

a number is multiplied by a base that's raised to an exponent:

Roundoff errors

a computer can not store an infinite amount of values so it must round it off eventually

if a computer can store x bits, what is the largest number it can store

2^x

ASCII encoding

analog data is

infinitely detailed

sampling

take a sample at regular time intervals. This step reduces the continuous time domain into a series of discrete intervals.

Quantization

reduces that continuous amplitude domain into discrete levels.

types of data stored in a computer using bits

numbers, text, photos, audio

we use lossy compression with

photos, videos, audio recordings