programming concepts (paper 2) Flashcards
what happens to data used in a program
it is stored in memory locations while the program is running
what is a variable
a data item held in memory which may change value during program execution
what is a variable referred to by
its identifier
what are the different types of data variable can be
- integer (5, -297)
- real (3.12, 9.999)
- char (A, @, $, 4)
- string (Yes, Hello world)
- boolean (TRUE, FALSE)
what is a constant
a value that cannot change during the execution of hte program (CONSTANT VAT <- 0.2)
what is the diifference between a variable and a constant
a variable can change during the program execution, a constant does not
what is an input
when the user inputs data or a request into the program to get an output (INPUT Name)
what is an output
it is used to output data on the screen after information has been processed by the user (OUTPUT “Area = “, Length * Width)
what is a boolean expression
something which uss one or more logical operators and evalutes to either TRUE or FALSE
what is a sequence control structure
when two or more statements are written and executed one after the other in sequence
what is a selectrion control structure
comprises an IF or CASE statement and a logical expression (CASE OF… OTHERWISE… ENDCASE…, IF… THEN…)
give an example of a nested if statement
IF Num1 >= Num2 AND Num1 >= Num3
THEN
OUTPUT Num1
ELSE
IF Num2 >= Num1 AND Num2 >= Num3
THEN
OUTPUT Num2
ELSE
OUTPUT Num3
ENDIF
ENDIF
what does a case statement actually allow to happen
one of several brances of code to be executed depending on what data has been inputed by the user
give me an example of a case statement
INPUT MemberType
CASE OF MemberType
“Junior” : EntryFee <- 2.0
“Senior” : EntryFee <- 3.0
“Special” : EntryFee <- 0.0
OTHERWISE OUTPUT “Invalid member type”
ENDCASE
what does iteration mean
repetition
what loop is count-controlled
FOR… NEXT
give an example of a FOR.. NEXT loop nested
FOR Table <- 2 TO 10
FOR N <- 1 TO 10
Answer <- Table * N
OUTPUT Answer
NEXT N
NEXT Table
what loop is condition controlled
WHILE… DO … ENDWHILE (pre-condition - checked at the start)
REPEAT… UNTIL (post-condition - checked at the end)
Give an example of a WHILE… DO… ENDWHILE loop
Total <- 0
Days <- 0
INPUT Visitors
WHILE Visitors <> -1 DO
Total <- Total + Visitors
Days <- Days + 1
INPUT Visitors
ENDWHILE
Average <- Total / Days
OUTPUT “Average daily number of visitors:”
OUTPUT Average
how is a string defined
as zero or more characters enclosed in quote marks (“”)
what are the different string functions and what do that do
- LENGTH(“ “) = returns the number of characters (including spaces)
- LCASE(“ “) = makes everything in parameter lower case
- UCASE(“ “) = makes everything in parameter upper case
- SUBSTRING(“ “, Num, Num) = makes everything in the quote marks outputed between the two numbers
what is a procedure
a named block of code, seperate from the main program, which can be called and executed using a statement like (CALL <procedure>)</procedure>
what does a procedure do
- it does not return a value
- control is passed using the CALL statement with any parameters in brackets
what is a function
a block of code which returns a value to a variable specific in the statement (eg you would have a function just for calculating the total of smt or the avergage)
what are parameters
values passed to the subroutine, which are delcared in the parentheses within the call instruction
what are functions and procedures essential in in the program life cycle
decomposition - breaking down a complex problem into smaller sub-problems and sub-tasks
what is a local variable
a variable which is only recognised inside a subroutine, if you were to call it in the main program then you would recieve an error message
what is a global variable
a variable which is recognised in the whole program, including all the subroutines
what are the two library routines
- the ROUND function
- the random number generation function
how would you write the round function in a psuedocode program
X <- 3.14159
Y <- ROUND(X, 2) //returns 3.14 in Y as it is 2dp
how would you write the random interger function in a psudocode program
RANDOM() // generates a random float point number between 0 and 1
what is an array
a data structure used to hold several elements of the same data type
how do you declare a 1D array, use this example of an array of 10 student names
DECLARE StudentName : ARRAY[1:10] OF STRING
how would you assign the name “Morris” to the third index of the array
StudentName[3] <- “Morris”
how do you declare a 2D array, use this example of a table of Sales over 4 months and three different shops
DECLARE Sales : ARRAY[1:3, 1:4] OF INTEGER
DECLARE Sales : ARRAY[1:3, 1:4] OF INTEGER
How many rows (horrizonal) are there in this array
3
DECLARE Sales : ARRAY[1:3, 1:4] OF INTEGER
How many collumns (verticle) are there in this array
4
how is data stored in a hard disk or SSD so that it can be written to
files
what is the purpose of storing data in a file to be used by a program
because then the file can be read or written into in many different programs, without having to re-enter the data all over again
what are the two different things you can do to a file
- read to it
- write to it
how would you open a text file on members to write
OPENFILE MemberFile.txt FOR WRITE
INPUT MemberID, Surname, Firstname
WHILE MemberID <> “END” DO
MemberRecord <- MemberID + “,” + Surname + “,” + Firstname
WRITEFFILE MemberFile.txt, MemberRecord
INPUT MemberID, Surname, Firstname
ENDWHILE
CLOSEFILE MemberFile.txt
how would you close a file
CLOSEFILE …..
how would you open a text file to read
OPENFILE MemberFile.txt FOR READ
how would you read to a file after opening it
READFILE MemberFile.txt, MemberRecord
WHILE NOT MemberFile.endOfFile DO
OUTPUT MemberRecord
READFILE MemberFile.txt, MemberRecord
ENDWHILE
CLOSEFILE MemberFile.txt
