coding Flashcards
integer
whole number
float/real
numbers with a decimal/fractional part
char
single ascii character
string
text - characters in quotes
boolean
true or false
variable
stores data
can change as program is executed
pseudocode - a<- 3
python a = 3
MOD
% in python
finds remainder
DIV
// in python
integer division
constants
declared in programming
value doesn’t change
pseudocode - all caps - space is _
eg A_VALUE
casing
converting to other data types
diff data types are represented diff in binary
string> int
int()
STRING_TO_INT()
casting to string
str()
INT_TO_STRING()
REAL_TO_STRING()
slicing a string
- SUBSTRING(start, end, str)
e.g. word = algorithm
SUBSTRING (3,6,word) = “orit” - print(word[3:7]) (stops before 7)
get letter at a certain position
x = word[0]
x = ‘w’
(python counts from 0)
length of a word
LEN(word)
len(word)
get position of a letter
POSITION(word, ‘r’)
word.index(‘r’)
word.find(‘r’)
make it upper case
UPPER(word)
word.upper()
make it lower case
LOWER(word)
word.lower()
flow chart
start/end - oval
process - rectangle
input/output - parallelogram
condition - diamond
structures
- sequence - all executed in order
- selection - if/else - next executed depends on if condition is true/false
- iteration - loops - repeat until condition met
selection structures
IF THEN - if :
ELSE THEN - else:
ENDIF
(or ELIF)
python comparison operators
not equal !=
greater than/equal to >=
less than/equal to <=
for loop
count controlled - run for a set no. times
for i in range(0,5):
FOR i<- 0 TO 5 DO
while loop
condition controlled - run until a condition is met
WHILE condition DO
ENDWHILE
after pseudocode structures
ENDWHILE
ENDIF
checks character is lower
character.islower()
checks character is digit
.isdigit()
make list of 1-4
list = [1, 2, 3, 4]
list <- [1, 2, 3, 4]
make empty list - with 6 slots in
list = [0]*6
list <- [6]
append to a list - add to end
list.append(7)
declaring empty list
list = [ ]
list <- [ ]
accesing a character in a list
print(list[0])
outputs whatever is in slot 0
replacing a number in a certain slot with another number
list[5]<- 17
list[5] = 17
slot 5 in the list is not 17
print items in list
for x in list:
print(x)
inserts an element in-between 2 elements in a list
list.insert(2, “A”)
adds A in space 2 after item one before item two
data structure
list - stores multiple data to a single identifier
useful
- can assign to a single identifier (lots of data)
- more efficient and readable - reduces code + organises data
2d list
list of lists
represent tables
people = [[“Bibi” , “15”], [“Amber”, “14”], [“Milan”, “15”]]
indexing a 2d list
people = [[“Bibi” , “15”], [“Amber”, “14”], [“Milan”, “15”]]
people[0][1] - evaluates to “15”
people[2][0] - evaluates to “Milan”
validation (check number is in certain range and forces user to type number in that range)
Number <- USERINPUT
WHILE Number < 0 or Number > 200 DO
OUTPUT “Number is out of range”
Number <- USERINPUT
END WHILE
subroutines
break up large complicated problems into smaller self contained subprograms
- functions or procedures
function vs procedure
function RETURNS a value
procedures just perform a task/execute code
built in subroutines
exist and can be called in programming languages eg print(), str(), int(), input(), len()
parameters
variables in a function - assigned value when you call it
why use a subroutine
- each subroutine can be tested separately - making it easier to debug
- many programs can work on a large program once - cutting down development time (splitting it up)
- subroutines can be reused - reducing development time
- code broken down into meaningful subroutines - easier to maintain
local variable
only exists whilst a subroutine is executing
can only be used + made + modified in the subroutine
- pass it in the parameter to use in a diff function eg def total(num)
global variable
accessible anywhere in the program - make something global by writing global in front of it
why use a function over a procedure
- returns one value which you can use multiple times anywhere in the code
(always store a function returned value to a variable to use later) (eg for function cal_total which stores total to use total twice - store to total_var = cal_total()
how to call a procedure
nameofprocedure()
normal data
acceptable data
boundary data
lowest and highest values accepted and numbers either side of the boundary
erroneous data
unacceptable data
repeat vs while loop
while - condition is checked at beginning
repeat until - checked at end so will always run once and checks conditions oppositely eg n =0 instead of n!=0
how to reduce errors
- comment on lines
- use subroutines
- test code
- use meaningful variable names
- use trace tables to document what’s happening
syntax error
dont follow programming rules - code stops (error message) eg dotn close brackets
logic errors
program still runs but won’t work properly
incorrect operator or symbols used by the programmer eg > instead of <
database
structured persistent collections of data on a computer stored in tables
- flat file / relational
field
column
record
row
+ databases
- efficient processing
- searching is easier and more organised
- Reduces storage requirements
- Reduces data redundancy
flat file databases
stores a single table of data inside a single text file
- stored using CSV
- each record is on a separate line.
- Each field is separated by comma
- hard to manage for complex data sets
- leads to redundancy and inconsistencies
primary key
Unique identifier each entity in a table
foreign key
when a primary key of one table is used in a different table to link the two tables
relational database
contains multiple tables, - each table holds data for one entity
- tables are related by common field
redundancy
when the same thing is repeated twice and given two separate primary keys
inconsistency
The same data is inputted twice but differently or incorrectly
relationship types
one to one
one to many
many to mant
SQL
structured query language - allows you to create query update and delete data from data bases
writing a selecting query
SELECT <field>
FROM <table>
use * to mean all fields</field>
writing a selecting query with a condition
SELECT <field>
FROM <table>
WHERE <condition></condition></field>
writing a select query for things between a range or search of patterns
BETWEEN in a range
LIKE search for pattern
SELECT <field>
FROM <table>
WHERE <field> (BETWEEN 5 AND 7) (LIKE ‘H’)</field></field>
writing a select query and sorting data
SELECT <field>
FROM <table>
WHERE <condition>
ORDER BY <field> ASC/DESC</field></condition></field>
changing a database
UPDATE <table>
SET <field> = <new>
WHERE <field> = <value></value></field></new></field>
deleting records from a database
DELETE FROM <table>
WHERE <field> = <value></value></field>
inserting in a record
INSERT INTO <table>
VALUES (“value1”, “value2”)
always put “ ” but for a date use a # #
querying a relational database
SELECT <field>
FROM <table> <table>
WHERE (<table.> = <table.primarykey>) BOOLEAN (<table.field> <comparison> <table.field>)</table.field></comparison></table.field></table.primarykey></table.></field>
