Unit 2a

Unit 2a

1. Data is raw, unorganised facts

   • Data types:
     • https://www.w3schools.com/python/python_datatypes.asp
     • String- more than one character, they are always in speech marks
       • str=37 print(str + str)= 3737 
       • In Python all input is accepted as a string so if you are inputting an integer or real number you must convert it before it is used in a calculation.
       • The "len" is the number of characters in a string
       • "Concatenating” means joining together
   • Array- a data structure that allows you to hold several values, all of the same type, with one name
     • https://www.w3schools.com/python/python_arrays.asp
     • an array of 10 integers called userName could be declared as : userName : array[0..9] of string
     • elements of an array can be referred to as : userName[0],userName[1] etc.
       • Username[2]=Username[2=1]: swapping the elements
     • initialising an array of 5 elements: mark=[0,0,0,0,0]
     • name = ["","",""] total = [0,0,0] averageMark = [0,0,0] no values have been assigned so they are empty at first

2. When data is processed, organized, structured or presented in a given context so as to make it useful, it is called information.

3. A constant is a value that cannot be altered by the program during normal execution, i.e., the value is constant.

4. Variable

   • a location in memory in which you can temporarily store text or numbers

5. Programming constructs

   • there are three basic ways of controlling the order in which program statements are carried out
   • Sequencing
   • Iteration
     • WHILE..ENDWHILE-does something when a set condition is true
     • FOR...ENDFOR-when you know how many times the code is to be repeated
       • also called a count controlled loop
     • REPEAT... UNTIL-does something until a set condition is true
   • Selection
     • "IF" statements are examples of selection statements
   • Declaring a variable is giving it a name and a type (String/int/ char/ float)
   • Assigning- a programming constant where a value is given to a variable.
     • a value can be incremented

6. Pseudocode

   • https://filestore.aqa.org.uk/resources/computing/AQA-8520-TG-PC.PDF -pseudocode specification
   • CODE_TO_CHAR
     • converts ASCII to characters
   • CHAR_TO_CODE
     • converts characters to their ASCII value

7. A file is a collection of records.

   • A record is a data structure consisting of a number of fields which can all be of different types
     • They are in table format.
     • A field is a single item of data in a record
   • A text file only contains strings
     • They can have several text fields separated by commas or other characters
     • the extension used is .txt
   • File handling
     • https://www.w3schools.com/python/python_file_handling.asp
     • open a new file starting with: newfile=open(" ")

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