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Computer Science PRAXIS study
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Software System Life Cycle - ANSWERSAnalysis -> Design -> Implement(Code) -> Test -> Maintain -> Analysis -> ... Top-Down Design (stepwise refinement) - ANSWERSbreak down into smaller and smaller pieces, easy to implement Bottom Up Design - ANSWERSuses pre-existing modules/libraries, saves time and effort Object oriented Programming (OOP) - ANSWERSinteracting objects, data centered, bundles actions and processes with data, very large projects can be developed more easily, modifications can be made without altering the "insides" 3 Big Ideas of OOP - ANSWERSabstraction(encapsulation), inheritance, and polymorphism Flowchart Shape: diamond - ANSWERSdecision (boolean) Flowchart Shape: rectangle - ANSWERSprocess Flowchart Shape: paralellogram - ANSWERSinput/output Flowchart Shape: oval - ANSWERSstart/end Unified Modeling Language (UML) - ANSWERSvisual organizer showing objects and contents UML visual example - ANSWERSName of class
Attribute name: type [set of variables, attributes, etc.]
Methods (parameters) . . . return type
Waterfall Development Model - ANSWERSlinear progress, works in industry, not software, clear and straightforward but rigid and difficult to modify, changes are costly idea -> analysis -> design -> develop -> test -> final Incremental Development Design - ANSWERSsmall amount done at a time, test and adjust as needed, completes entire process in each increment, flexible to change, includes customer testing plan -> analyze,design,implement(development) -> test -> evaluate -> plan -> ... Spiral Development Design - ANSWERSincludes risk analysis, documentation is difficult, uses prototyping and best parts of other models, costly and complex to manage communicate -> plan -> model -> construct -> deploy -> communicate -> ... Agile Development Design - ANSWERScommonly used in software development, can cause loss of focus or more complex project, risk of going over budget, incremental and iterative, flexible sprint - set small simple short-term goals, achieve, test, evaluate, repeat some common examples: SCRUM, XP, Kanban code style conventions for constants - ANSWERSCAPS code style conventions for class - ANSWERSFirstlettercapital code style conventions for method/variable - ANSWERSCamelCase Precondition - ANSWERSwhat must be true for the code to be executed Postcondition - ANSWERSwhat will be true after the code is executed Robust Program - ANSWERSable to withstand adverse conditions ("handle exceptions") Unit Testing - ANSWERSprocess of testing each individual process Input Protection/Data Validation - ANSWERSinclude a test of the form of input data Exception - ANSWERSerror in programming (checked or unchecked) Exception Handling - ANSWERSprotecting against exceptions Try Catch Block - ANSWERScommon exception handler string try {...} catch {...}
Polymorphic Objects - ANSWERStype of polymorphism, parent can reference any child or grandchild ex) furniture -> wooden furniture -> chair a chair is still also furniture Instruction Set Architecture (ISA) - ANSWERSpart related to programming (native data types, instructions, external input/output, exception handling, registers, memory architecture) Complex Instruction Set Computing (CISC) - ANSWERSmicro-processor architecture, the machine instruction set designated as complex, primarily used by Intel and Intel Pentium; processors contain numerous instruction sets Reduced Instruction Set Computing (RISC) - ANSWERSmicro-processor architecture, few instructions, limiting to frequently used instructions, used by MacIntosh and Apple Computer Architecture - ANSWERSrelates to the way circuit boards and processors are designed and defined (CPU most significant) Operating System (OS) - ANSWERSsoftware that manages hardware and provides common services Disk Operating System (DOS) - ANSWERS1966, first widely installed OS, operates using the command line, mainly IBM 1981- Windows OS - ANSWERS1.0 released 11/20/1985, XP - used underpinnings advanced security, stability, efficiency vista - 2006, windows search, DVD maker, aimed to increase peer to peer file sharing windows 8 - 2012, optimized for touch systems Unix - ANSWERSfamily of multitasking, multiuser OS derived from AT&T, developed 1970s by Bell Labs, Ken Thompson, Dennis Ritchie Linux - ANSWERSLinus Torvalds 10/5/1991, Unix-like open-source software, defining component was Linux kernel Mac OS - ANSWERS1984, graphical user interface OS, Apple and MacIntosh Mac OSX 2001 GM-NAA I/O - ANSWERS1956, forst OS for IBM 704 computer, General Motors, aeronautical research Master Control Program (MCP) - ANSWERS1961, first OS with multiple processors, first commercial implementation of virtual memory, first OS written exclusively in a high level language
Artificial Intelligence - ANSWERSlogic processes performed by software using sophisticated logic and large database systems Low Level Language - ANSWERSeasy for computer to understand and execute, written in machine code High Level Language - ANSWERSeasy for human to understand, must be translated into machine language to execute Machine Code - ANSWERSoriginal low level language, rows of switches flipped on or off by operator Assembly - ANSWERSone step above machine, made easier to express programs, converts to machine code Two Ways to Translate High Level Language to Machine Code - ANSWERSinterpret compile Interpret - ANSWERStranslated and executed line by line Compile - ANSWERStranslate all, then execute Three Paradigms of High Level Language - ANSWERSprocedural functional object oriented Procedural (Structured Programming)(Imperative Languages) - ANSWERSfirst to develop, contain step-by-step instructions ex) Fortran, Cobol, Pascal, C Functional - ANSWERS"mathy", given data, recursion primary way to iterate process ex) LISP, Haskell, Scheme Object Oriented (OOP) - ANSWERSactions and data bundled in objects defined by classes ex) C++, Java, Python Fortran (Formula Translation) - ANSWERS1950s John Backus, used for science and engineering COBOL - ANSWERSlate 50s/early 60s Grace Hopper, used for business BASIC (beginner's All-Purpose Symbolic Instruction Code) - ANSWERS1964 Dartmouth College, easy to learn and use, good for new or young programmers
string - ANSWERSdata type, multiple entry text, "enclosed in double quotes" boolean - ANSWERSdata type, true or false, 1 or 0 byte storage and limits - ANSWERS8 bits, values from -128 to 127 short storage and limits - ANSWERS16 bits, values from -32,768 to 32, int storage and limits - ANSWERS32 bits long storage and limits - ANSWERS64 bits char storage and limits - ANSWERS16 bits, cousin to int, number represents characters in ASCII/UniCode ex) A=65, a=97, 0= Wraparound - ANSWERSreaching the end of an integer value and looping around to the other end ex) byte num -> 127 num <- num + 1 print (num) *output is -128 because byte max value is 127 float storage precision - ANSWERS32 bits, loses precision beyond 7 decimals double storage precision - ANSWERS64 bits, loses precision beyond 15 decimals Variable - ANSWERSlocation in memory containing a changeable value Constant - ANSWERSmemory location cannot be changed once assigned Declare - ANSWERSassign name Instantiated - ANSWERSassign a value to a declared variable <- or = symbols used a valid variable name... (5 identifier rules) - ANSWERS1. Must contain only letters, numbers, and underscore
- Must begin with letter or underscore
- May not contain symbols
- May not contain spaces
- May not be a reserved word from the language coding conventions (6 rules of thumb) - ANSWERS1. classes start upper case
- procedures, functions, and methods start lower case
- camelCase multiple word identifiers
- CONSTANTS are all caps
- use meaningful names
- abbreviate within reason True or False: Assignment statements are "left to right" operation. - ANSWERSFalse, they are right to left operations, the right side compiles first, i.e. comp sci is not commutative ex) num = 7 is good ex) 7 = num is bad <- or = - ANSWERSassign == - ANSWERSequal != - ANSWERSnot equal += - ANSWERSadd -= - ANSWERSsubtract *= - ANSWERSmultiply /= - ANSWERSdivide Primitive - ANSWERSstored and accessed directly in memory ex) boolean, char, float, int Object - ANSWERSmemory address contains a pointer to tell where to access ex) string, array Sequential Processing - ANSWERScontrol structure that runs in sequence (order) Operator - ANSWERSbasic building blocks of programming statements Method - ANSWERSblocks of code that allow processes anywhere in the program Parameter - ANSWERSaspect of a method that defines the info receoved and processed Conditional Processing - ANSWERScontrol structure that allows program to do "this" or "that" based on some condition 4 types of errors - ANSWERSlexical, syntax, runtime, logic
User-defined Method - ANSWERSmade by programmer Library Method - ANSWERSpre-existing as part of the language What is the return type: void f2 (int n) int k <- 0 while (k formal parameter (receive value)(in method header) - ANSWERStemporary local variable that receives a value from a method call. once method completes its task the formal parameter ceases to exist What is the formal parameter: void doStuff (int x) print "the number is " + x - ANSWERSint x What is the actual parameter: void main doStuff (4) int a <- 42 doStuff (a) - ANSWERS4 and a are both actual parameters Pass by Value - ANSWERScopy of info sent from actual to formal, changes do not affect original ex) fax Pass by Reference - ANSWERSactual memory location of original sent to formal, changes affect original ex) google doc Pass Parameter - ANSWERSprocess of a program passing data from one section to another Black Box - ANSWERSdevice, system, or object viewed in terms of input/output without any knowledge of its internal workings and a well explained interface ex) phone, TV, fridge Subroutine - ANSWERSinstructions for a task, chunked together and named. allows for complexity as a single concept Black Box Rule - ANSWERSthe interface of a black box should be fairly straightforward, well-defined, and easy to understand Black Box Testing (Behavioral Testing) - ANSWERSinternal structure/design of item tested is unknown to tester, usually a functional test Black Box testing attempts to find errors in... - ANSWERSincorrect/missing functions interface data structures or external database access behavior or performance initialization and termination
while do while repeat until Recursion - ANSWERSform of iteration where process iterates until a base condition is reached which loops are pre test loops? - ANSWERSwhile and for. they may never act check -> action -> step which loops are post test loops? - ANSWERSdo while and repeat until. always act at least once action -> step -> check Recursion - ANSWERSsolution to a process involves that process calling another instance of itself over and over ex) my #=Bob's +1, Bob's #=Ted's +1, Ted's #= I can't get my number until the entire process finishes Base Case - ANSWERSterminating situation or scenario of recursion (no base case results in infinite recursion, which locks up working memory forcing a reboot by user) Recursive Case - ANSWERSone of two situations in recursion (the other is base case), another call is made moving closer to the base case True or False: Recursion and Loops are identical. - ANSWERSFalse. recursion can do anything a loop can but not vice versa. recursion is memory intensive and should only be used when a loop cannot Array - ANSWERSone-dimensional or multi-dimensional containing one data type, memory used by an array is static (not able to change size once declared), easy to access contiguous memory (side-by-side) with indexing Linked List - ANSWERSlinear data structure consisting of nodes that link to next node, similar to an array, but no contiguous memory. able to grow or shrink in size, more difficult to manage Instantiate an Array - ANSWERSdecalre entire set of values when name is declared Linear Data Structure - ANSWERSoccupies contiguous memory print len(listname) or print listname.length - ANSWERSoutputs array length
2-dimensional Array - ANSWERSan array of arrays, characterized by rows and columns, still contiguous and static memory Row Major - ANSWERSrow then column index order ex) arrayname [row][column] Ragged Array - ANSWERSnumber of columns in each row may be different Length of a 2D Array... - ANSWERSlength is the number of rows *to find length of columns use print arrayname[row index #] How to Substantiate a 2D Array - ANSWERSint [][] arrayname<- {{1, 2, 3}, {4, 5, 6}} or int[][] arrayname<- new int[5][3] creates an empty 5x3 array Stack - ANSWERSabstract data type, considered LIFO (last in first out) array, only the top of the stack is accessed Push (stack) - ANSWERSplace on top Pop (stack) - ANSWERSremove top after copying value Peek (stack) - ANSWERScopy top value without removing Queues - ANSWERSFIFO (first in first out) data structure, new entires go to back, removes entries come from front (like a line) Push (queue)/Enqueue - ANSWERSplace at back Pop (queue)/Dequeue - ANSWERSremove front after copying value Peek (queue) - ANSWERScopy value at front without removing Node - ANSWERSobject linked to other objects 2 parts of a node - ANSWERSdata field and next Dynamic Memory - ANSWERSmemory that is not contiguous, is allocated, or removed, as needed (can grow or shrink) Head - ANSWERS1st object in a linked list Null - ANSWERSname for the place after the last node in a linked list
step3 to output remove root step4 place last node as root step5 heapify step6 repeat until done Graph - ANSWERSvisual representation of connection of nodes Vertex - ANSWERSnodes of a graph Edge - ANSWERSconnections in a graph (branches) Directed Graph - ANSWERSedges have direction Undirected Graph - ANSWERSedges have no direction Adjacency Matrix - ANSWERSgrid used with a graph to see connections each node labeled on top and left axes 0 if no direct connection 1 if direct connection exists Access Modifier (Access Specifier) - ANSWERSkeywords in OOP that set accessibility 2 most common are public and private Construct - ANSWERSprocess of instantiating an object based on a class definition Constructor - ANSWERSmethod in class definition whose sole responsibility is to construct a new object New - ANSWERSreserved word that asks compiler to instantiate a new object Accessor Methods - ANSWERSstart with "get", allows and controls access to private data of objects Concrete Class - ANSWERSclass that can be directly created then used (we can create an object from a concrete class definition) Abstract Class - ANSWERSparts are declared abstract we cannot directly substantiate an object from (allows initializing without details in class definition, all details are declared in client code) Interface - ANSWERSall elements abstract, no data, no implementations, only names of methods and their basic purpose ex) mouse, touchscreen, console controller
compareTo () - ANSWERScompares this object with specified object and returns a value 0 means objects are equal, -1 means current precedes, 1 means current is after Algorithm Analysis - ANSWERSprocess determines amount of resources needed to execute a particular algorithm Constant Run Time - ANSWERSO(1) always one step ex) can contiguous data Linear Run Time - ANSWERSO(N) equal to number of pieces of data ex) output an array Logarithmic Run Time - ANSWERSO(logN) powers of 2 ex) binary search Quadratic Run Time - ANSWERSO(N^2) ex) selection sort, bubble sort, insertion sort Linear Search - ANSWERSloop based, starts at 1st and continues to end of list until target found or end of array is reached Big O for linear search - ANSWERSbest case O(1) avg case O(N) worst case O(N) Binary Search - ANSWERSsearch through ordered set using "divide and conquer" *set must be ordered Big O for binary search - ANSWERSbest case O(1) avg case O(logN) worst case O(logN) Selection Sort - ANSWERSfind the best value for the position linear search for lowest, when found swap for 1st spot, repeat for every spot *code involves a 3-step swap process Big O for selection sort - ANSWERSbest case O(1]N^2) avg case O(N^2) worst case O(N^2)
WAN, connects LANs Hub/Switch - ANSWERSoften in same device as router, interconnects all device in a local network connects nodes in LAN hub dilutes bandwidth, switch is more used Node/Host - ANSWERSany single device in a network ex) router, hub, PC, mac, fax TCP/IP (transmission control protocol/internet protocol) - ANSWERSprotocol of the internet, 4 layer network model internet works on OSI (open systems interconnection) - ANSWERSmainly used for teaching network concepts, 7 layer theoretical network model internet is based on LAN (local area network) - ANSWERSnetwork in a small area such as home, office, or school. gains access to outside world through router, uses system of switches for connectivity within the local network WAN (wide area network) - ANSWERSnetwork in large area such as city, country, or continent, interconnected using routers ex) internet RIP (routing information protocol) - ANSWERScommunication language of routers, keeps track of best pathways to use and lookup tables for other routers html (hypertext markup language) - ANSWERScoding language used by web browsers to control info on web pages SMTP (simple mail transfer protocol) - ANSWERSmailman of the internet, used to send/receive email POP (post office protocol) - ANSWERSused to store email until it is ready to be accessed Ethernet - ANSWERSLAN protocol primarily used by internet with wires, wireless, and fiberoptics to connect to routers Ring Topology - ANSWERSLAN topology once used with token ring protocol, long abandoned in favor of Ethernet Bus Topology - ANSWERSonce common, all devices in network connected to single cable or line, also abandoned for Ethernet
Star Topology - ANSWERSmost prevalent today, uses hub/switch as connecting device at center of star Tree Topology - ANSWERScombination of bus and star MAC address system (media access control) - ANSWERSevery network device has a unique, unchangeable 48-bit physical address. often in hex digit form where each digit represents bits of info 01:23:45:67:89:ab unique to every device in existance IPv4 (internet protocol, version 4) - ANSWERSeach internet device has a 32-bit address that can change relative to where it plugs in to the network 32bits=4 bytes IPv6 (internet protocol, version 6) - ANSWERSnewer IP address system, 128 bits, greatly increses supply of available worldwide .com - ANSWERScommercial .org - ANSWERSnon-profit .net - ANSWERSsmaller website systems .edu - ANSWERSeducational institutions .gov - ANSWERSgovernment .mil - ANSWERSUS military .us - ANSWERSUnited States .au - ANSWERSAustralia .ca - ANSWERSCanada .uk - ANSWERSUnited Kingdom Bomb - ANSWERSvirus with built in time delay Botnet - ANSWERSbots connected to a command and control server Phishing - ANSWERSfake emails/sites designed to aid in identity theft
