AP Computer Science Principles Unit 3 Notes

APCS Unit 3 Notes 3.1:  String- a linear sequence of characters, words, or other data  Dichotomous- in which something can only be one thing or another (yes or no)  Binary code- code represented with the two symbols of 1 and 0  Bits- the foundation for digital computing (1s and 0s) - short for binary digits  Digital- how information is stored, accessed, transformed and used by computers  State space- the space of potential possibilities  Exponential growth- the rate of growth that rapidly increases in proportion to the growing total number or size.  Fixed-point numbers- numbers where the decimal point is always in the same place.  Floating-point numbers- numbers where the decimal point can float because there is no fixed number of digits before and after the decimal point. AKA: real numbers  Real numbers- numbers approximated by floating-point representations that do not necessarily have infinite precision.  Scientific notation- the mathematical representation of a decimal number in floatingpoint form. Examples: 4 x 10³ for 4,000, 4.002 x 10³x 10 for 4,002 or 2.345E6 for 2,345,000. 3.2:  Decimal- describes the base-10 number system. The most commonly used number system.  3.3:  ASCII (American Standard Code for Information Interchange)- a table that outlines a common set of conventions established for converting between binary values and alphanumeric (represents 128 different characters)  Alphanumeric- the characters that consists of uppercase and lowercase letters in addition to numerals 0-9.  Digital noise- irrelevant or meaningless data that has found its way into otherwise meaningful code.  Abstraction- the process of removing or suppressing details to create a manageable level of complexity.  Bit string- a sequence of bits that can be used to represent sets or to manipulate binary data.  Mapping- associating each element of a given set with one or more elements of a second set.  Data- characters, symbols or quantities on which operations are performed, stored and/or transmitted by a computer.  Unicode- a binary encoding system that can represent much more of the world's text than ASCII can (represents 65,536 different characters)  AMONG US SUSSY BAKA! 01000001 01001101 01001111 01001110 01000111 00100000 01010101 01010011 00100000 01010011 01010101 01010011 01010011 01011001 00100000 01000010 01000001 01001011 01000001 00100001 3.4: 3.5:  Morse Code- a code where letters are represented by combinations of long and short signals of light or sound.  Baudot Code- a binary code invented by Emile Baudot in 1870 that uses crosses and dots in order to encode 2^5 or 32 characters.  Variable-width encoding- using codes of different lengths to encode a character set for representation (example: Morse Code)  Fixed-width encoding- using codes with a fixed width to encode a character set for representation (example: Baudot Code) 3.6:  Discrete- separate or divided (digital)  Continuous- unbroken, without interruption (analog)  Approximation- digital copies are only approximations of the natural object.  Analog- non-digital signals or information represented by a continuously variable physical quantity such as spatial position or voltage. 3.7:  List- A list is an ordered sequence of elements. For example, [value1, value2, value3, …] describes a list where value1 is the first element, value 2 is the second element, value 3 is the third element, and so on.  Element- An element is an individual value in a list that is assigned a unique index.  Data structure- a particular way of organizing and storing data such as an array, table, etc.  Data abstraction- help manage complexity in programs by giving a collection of data a name without referencing the specific details of the representation.  Index value- the representation of the location of each item in a list. 3.8:  Output- observable behaviors generated by the computer such as animation, sound, and text.  Join- the "join" block in Scratch concatenates, or links two values together. Example: "hello" and "there" would result in "hellothere".  Linear search- a method for finding a target value within a list (whether presorted or not) by checking each value until a match is found or until all the elements have been searched.  3.9:  Procedure- a group of blocks that are combined to perform a specific task.  Substring- a subset of a string of alphanumeric fields or variables.