Computing

Computing

1. my cat says meow. My cat technically doesn't exist, but that's only a technicality. Enjoy the lesson :|

   • SECTION 1
     • Computational thinking
       • Algorithm
         • A step by step set of instructions that can be followed to complete a task
         • Made by either pseudocode or flowchart
           • pseudocode
             • Not similar to any individual programming language, but can be easily transferred into any language
             • CODE_TO_CHAR and CHAR_TO_CODE convert to and from ascii codes
           • flowchart
             • Shows the process the program will go through using symbols
               • oval=start/end(terminators)
               • rectangle=process, step
               • diamond=decision
               • paralellogram=assignment
       • Decomposition
         • Breaking the problem up into smaller problems that are easier to solve
       • Abstraction
         • Removing the irrelevant details so that you can focus on the important problem
       • Selection
         • P
         • When there is a choice of paths that could be taken-if statements
       • Programming constructs
         • Sequencing
           • Putting things in the order they are meant to be executed in
             • If you're asked for an example of sequencing write two things that happen next to each other
         • Iteration
         • Assignment
           • Making a variable
       • Pattern recognition
     • Searching, sorting and complexity
       • Searching
         • Binary search
           • The list must be in order
             • Take the middle value
               • If it is what we're looking for, stop
                 • Else if it is larger than the one we're looking for, take the values to the left of the middle value
                   • If it is smaller than the one we're looking for, take the values to the right of the middle value
                     • Repeat with the new list
           • In a list of 2^n, the number of items examined in the worst case is n+1
             • e.g. in a list of 16--2^4-- items the maximum number that will be examined is 5--4+1
         • Linear search
           • Look at each element one by one until you find the one you want. Way less efficient than binary search
       • Sorting
         • MergeSort
           • Split all the elements into individual lists
             • Merge the lists into lists of two
               • Call itself, to merge the lists into lists of 4
                 • Repeat until merged
                 • Notes: It is recursive
                   • Uses a lot of memory to store the sublists
                     • Quicker than bubblesort
         • Bubblesort
           • Take the first element and the second element from the list
             • IF element1>element 2 THEN
               • Swap them
                 • ELSE
                   • Do nothing
                     • REPEAT: Move along the list to the next pair
                       • IF no more elements THEN go to element1
                         • ELSE: Go to element 2
                           • UNTIL no changes need to be made
                           • Note: I don't understand this
                             • Quite slow
         • After the list is sorted, one more pass is needed for the computer to check that it's sorted
       • Complexity
         • In the worst case, the number of comparisons needed
           • Bubble sort complexity=n^2 where n=length of list

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4. SECTION 2

   • variables n stuff
     • Data=unprocessed numbers, figures, graph etc
     • Information=Data that has been processed and given a meaning
     • Data type=how data is stored eg integer
     • Constant=A value that stays the same throughout the program
       • In pseudocode, you can write them like variables except put them in capital letters
       • Used so that you have a variable that never changes
         • You can go and assign a new value to a constant, but the computer cannot
     • Variable
       • A temporary storage device that can later be used by the program
         • In python, variables cannot start with numbers
           • Variables are case sensitive
     • Increment=increase by 1
     • mod=what is the remainder when you divide one number by the other?
       • div=integer division, 17div3=5
     • Changing the data type of a variable is called CASTING
   • when you put strings together,it is called CONCATINATION
   • iteration
     • for loop also called count controlled loop
       • there is also a while loop (ofc), and a repeat until loop which is not in python and some other languages
       • for when you know how many times you want to repeat it
     • Pseudocode
       • WHILE...ENDWHILE
       • fOR...ENDFOR
       • REPEAT...UNTIL
         • same as while loop except condition is checked at end rather than beginning
   • Arrays
     • Holds multiple data values of the same type with one name
     • access elements like variable[0],variable[1],etc
     • one dimentional and two dimentional arrays- a 2d array is an array of arrays
   • Files and Records
     • A file is something.txt- a text thingy
       • A record is a table.But we don't need to know abouyt them
       • Create a txt file. Make it in the same folder as the program is to avoid long thingys.
         • Use open() to create a file
           • eg. newfile=open("The New File.txt","w")
             • newfile, the variable, is called a file handler
             • newfile.write("HELLO")

5. yay this is such a colourful mind map !!!

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