2 - Programming

Question 1

What are data types? Give some examples of some:

Answer 1

-data types describe the different types of data being used, and defines the range of values a variable may take

-int, real, bool, char, string

in python, real numbers are called floats

Question 2

Why are data types needed?

Answer 2

-so the computer knows what operations it can perform on it
-it allocates the necessary amount of memory to optimise the program

in python, real numbers are called floats

Question 3

What is a variable?

Answer 3

named identifier that holds a value in memory that can change

Question 4

What is a constant, and what is it used for?

Answer 4

-named identifier that is given a value when initialised and holds it in memory, and doesn’t change throughout the program

-used to reference known values like pi

Question 5

Define declaration/initialisation:

Answer 5

-naming a new identifier for the first time

-then assigning it a value

In Python, both are usually done at the same time, but some languages (like VB) do it separately

Question 6

What is an identifier?

Answer 6

a name for a variable, constant, or subroutine

Question 7

Why should you give meaningful identifier names?

Answer 7

-meaningful identifier names describe the purpose of the variable
-makes the program easier to interpret/debug

Question 8

What are the 3 programming constructs?

Answer 8

-sequence
-selection
-iteration

Question 9

What is sequence in programming?

Answer 9

executing 1 instruction after another (imperative programming)

Question 10

What is selection in programming?

Answer 10

statements that change the flow of a program based on conditions that are met (branching)

Question 11

What is iteration in programming? Describe the 3 types:

Answer 11

repeated execution of a section of code

for - count controlled

while - condition checked at start, may never run
repeat until - condition checked at end, always runs once

The bottom 2 are condition controlled

Question 12

What is nesting?

Answer 12

putting a statement inside another with selection/iteration

Question 13

Name 3 types of arithmetic division and give their Python symbols:

Answer 13

-real division, just normal ÷

/

-integer division, DIV, division that returns the integer part of the result

//

-remainder division, MOD, returns remainder

%

Question 14

Name the boolean operators:

Answer 14

NOT
AND
OR

Question 15

What are data structures?

Answer 15

an abstract idea of how to store and access data in a computer system

Question 16

Why are data structures described as abstract?

Answer 16

-the computer memory doesn’t actually know it is a list, it just stores it in memory as it usually would

-it just makes it easier for the programmer to read/access

Question 17

What is an array?

Answer 17

a data structure (1 or 2 dimensional) comprised of a set number of cells containing data all of the same type

Question 18

How do you access data from a 2D array?

Answer 18

-the first square bracket indicates the list you want to access from the 2D array
-the second square bracket indicates the item from the previously specified list

remember indexing starts from 0

Question 19

What is a record?

Answer 19

a data structure containing a set of information about certain items

Question 20

How would you make a record in python without importing anything?

Answer 20

make a dictionary where the key is the name of the item, and the value is all the information about the item in the form of another dictionary

record = {
 "bob":{"score":102,"name":"bob name},
 "john":{"score":321,"name":"john name"},
 "fred":{"score":7,"name":"fred name"}
}

Question 21

Using an import statement, how could you make a record in python?

Answer 21

if you are making more than one dataclass, always put @dataclass before it

Question 22

How do you add a record to a dataclass?

Answer 22

make sure you give a value to every one of the arguments when adding a record

Question 23

How do you access a particular value from a record in a dataclass?

Answer 23

Question 24

Describe a dictionary:

Answer 24

dict = {key1: value1, key2: value2}

-values can be accessed by doing dict[key]

Question 25

What is the code for making substrings?

Answer 25

```myString[a:b]``` a, start b, end (not included)

Question 26

How do you make a string in all capitals or lower case?

Answer 26

``` myString.upper() myString.lower() ```

Question 27

How do you find a particular character or word within a string?

Answer 27

`myString.find("a bc")` -returns integer that shows the position of the first character in the find brackets -if it doesn't find it, then it will return -1

Question 28

How do you reverse a string?

Answer 28

myString[::-1]

Question 29

What is another way to concatenate some variables in a print statement?

Answer 29

always put the f before so that it recognises the formatting needed

Question 30

Functions for converting to character code and back:

Answer 30

ASCii to text: ```chr(myAsc)``` Text to ASCii: ```ord(myChar)```

Question 31

How do you generate a random number in python?

Answer 31

``` import random num = random.randint(startRange,endRange) ```

Question 32

What is the difference between randint and randrange?

Answer 32

-randint takes a random number between the start and end numbers *inclusive* -randrange does not include the end number ## Footnote However both are used in the same way - (random.randint(), random.randrange())

Question 33

How do you use shuffle?

Answer 33

``` import random list = [1,2,3,4,5,6,7,8,9] random.shuffle(list) ``` ## Footnote **DO NOT** put the last line in a print statement, it doesn't work for some reason

Question 34

What is a subroutine, and how is it used?

Answer 34

-indented block of code used in order to execute a commonly used task -can be called by writing its identifier name as a statement and passing the necessary parameters

Question 35

What is the difference between a global and a local variable?

Answer 35

global is can be accessed/changed throughout the whole program, while local only exists within a certain subroutine

Question 36

What are the advantages of local variables over global ones?

Answer 36

-easier to debug program as variable can only be accessed within its own subroutine -more memory efficient as once the subroutine finished, all of the local variables used in it are removed from memory

Question 37

Difference between a procedure and a function:

Answer 37

functions return a value ## Footnote Functions can also return a value as a string, eg: `return "num1"` This won't print the string but assign it to the variable where the function was called

Question 38

Why was the structured approach to programming developed?

Answer 38

to give programmers a logical structure that uses modules/subroutines to aid code interpretation/debugging

Question 39

What are the advantages to using modularised programming in the structured approach of programming?

Answer 39

-can be reused to reduce development time -easier to find errors in code -can be changed without affecting the rest of the program -subroutines can be developed separately by different people and combined later on ## Footnote Make sure to put the first point as a whole, don't just put "reduces development time" by itself

Question 40

A programmer uses the code below in order to make a program. Explain how they have used the structured approach to programming:

Answer 40

-decomposed the problem into sub-problems -solved sub-problems by using subroutines and passing the necessary parameters

Question 41

What is robust and secure programming?

Answer 41

writing sections of code to catch errors from invalid user inputs that wouldn't usually be expected

Question 42

Types of testing data:

Answer 42

-valid data, within accepted bounds -invalid/erroneous data, rejected by program -boundary/extreme data, either side of bounds ## Footnote If asked to give an example of boundary data, just give one value rather than giving both sides of the boundary

Question 43

Name the different types of validation checks:

Answer 43

*range check* - for numbers *length check* - for strings *presence check* - eg checking if a password has been entered a second time *format check* - eg checking if your date of birth is in the form DDMMYYYY *type check* - eg checking if a number is an integer

Question 44

Name 2 types of errors:

Answer 44

-syntax (misspelt code, eg missing punctuation/letters) -logic (program can run but not as intended, eg bool value is true rather than false)

Question 45

A program has the statement: `if distance <= 5:` How many possible values could the result of this comparison have?

Answer 45

2 (either distance is less than/equal to 5, or it is greater than 5) ## Footnote boolean