Exam Reference Language - GCSE Computers

Examination questions will be written in OCR Exam Reference Language for clarity and consistency.

Operators

The following operators will be used consistently in examination questions.

Comparison Operators

Operator	Description	Operator	Description
`==`	Equal to	`<=`	Less than or equal to
`!=`	Not equal to	`>`	Greater than
`<`	Less than	`>=`	Greater than or equal to

Arithmetic Operators

Operator	Description	Operator	Description
`+`	Addition	`/`	Division
`-`	Subtraction	`MOD`	Modulo
`*`	Multiplication	`DIV`	Quotient
`^`	Exponent

Boolean Operators

Operator	Description
`AND`	Logical AND
`OR`	Logical OR
`NOT`	Logical NOT

Core Constructs & Casting

Syntax and Examples

Concept	Keyword(s) / Symbols	Example
Commenting Comment	`//`	`//This function squares a number function squared(number) squared = number^2 return squared endfunction //End of function`
Variables Assignment	`=`	`x = 3 name = "Louise"`
Constants	`const`	`const vat = 0.2`
Global Variables	`global`	`global userID = "Cust001"`
Input/Output Input	`input(...)`	`myName = input("Please enter a name")`
Output	`print(...)`	`print("My name is Noni") print(myArray[2,3])`
Casting Converting to another data type	`str()` `int()` `float()` `real()` `bool()`	`str(345) int("3") float("4.52") real("4.52") bool("True")`

Control Structures Selection & Iteration

Selection

Concept Keyword(s) / Symbols Example

Selection
IF-THEN-ELSE

if ... then
elseif ... then
else
endif

if answer == "Yes" then
  print("Correct")
elseif answer == "No" then
  print("Wrong")
else
  print("Error")
endif

CASE SELECT or SWITCH

switch ... :
case ... :
default:
endswitch

switch day :
  case "Sat":
    print("Saturday")
  case "Sun":
    print("Sunday")
  default:
    print("Weekday")
endswitch

Iteration

Concept	Keyword(s) / Symbols	Example
Iteration FOR loop (Count-controlled)	`for ... to ...` `next ...`	`for i=0 to 9 print("Loop") next i` This will print the word "Loop" 10 times, i.e. 0-9 inclusive.
FOR loop with step	`for ... to ... step ...` `next ...`	`for i=2 to 10 step 2 print(i) next i` This will print the even numbers from 2 to 10 inclusive. `for i=10 to 0 step -1 print(i) next i` This will print the numbers from 10 to 0 inclusive, i.e. 10, 9, 8,..., 2, 1, 0. Note: the `step` command can be used to increment or decrement the loop by any positive or negative integer value.
WHILE loop (Condition-controlled)	`while ...` `endwhile`	`while answer != "Correct" answer = input("New answer") endwhile` Will loop until the user inputs the string "Correct". Check condition is carried out before entering loop.
DO UNTIL loop (Condition-controlled)	`do` `until ...`	`do answer = input("New answer") until answer == "Correct"` Will loop until the user inputs the string "Correct". Loop iterates once before a check is carried out.

String Handling & Operations

String Operations

Concept	Keyword(s) / Symbols	Example
String length	`.length`	`subject = "ComputerScience" subject.length // gives the value 15`
Substrings	`.substring(x, i)` `.left(i)` `.right(i)`	`subject.substring(3,5) // returns "puter" subject.left(4) // returns "Comp" subject.right(3) // returns "nce"` `x` is starting index; `i` is number of characters; 0 indexed.
Concatenation	`+`	`print(stringA + stringB) print("Hello, your name is: " + name)`
Uppercase	`.upper`	`subject.upper // gives "COMPUTERSCIENCE"`
Lowercase	`.lower`	`subject.lower // gives "computerscience"`
ASCII Conversion	`ASC(...)` `CHR(...)`	`ASC('A') // returns 65 (numerical)` `CHR(97) // returns 'a' (char)`

File Handling & Arrays

File Handling

Concept	Keyword(s) / Symbols	Example
Open	`open(...)`	`myFile = open("sample.txt")` Note: the file needs to be stored as a variable.
Close	`.close()`	`myFile.close()`
Read line	`.readLine()`	`myFile.readLine() // returns the next line in the file`
Write line	`.writeLine(...)`	`myFile.writeLine("Add new line")` Note: the line will be written to the END of the file.
End of file	`.endOfFile()`	`while NOT myFile.endOfFile() print(myFile.readLine()) endwhile`
Create a new file	`newFile()`	`newFile("myText.txt")` Creates a new text file called "myText". The file would then need to be opened using the above command for Open.

Arrays

Concept Keyword(s) / Symbols Example

Declaration

array colours[...]

array colours[5]
// Creates 1D array with 5 elements (index 0 to 4).

array colours = ["Blue", "Pink", "Green", "Yellow", "Red"]
// Arrays can be declared with values assigned.

Arrays are 0 indexed
Arrays only store a single data type

array gameboard[..., ...] = ...

array gameboard[8,8]
// Creates 2D array with 8 elements (index 0 to 7).

Assignment

names[...] = ...
gameboard[..., ...] = ...

names[3] = "Noni"
gameboard[1,0] = "Pawn"

Sub programs & Random Numbers

Sub programs

Concept	Keyword(s) / Symbols	Example
Procedure	`procedure name(...)` `endprocedure`	`procedure agePass() print("You are old enough to ride") endprocedure procedure printName(name) print(name) endprocedure procedure multiply(num1, num2) print(num1 * num2) endprocedure`
Calling a procedure	`procedure(parameters)`	`agePass() printName(parameter) multiply(parameter1, parameter2)`
Function	`function name(...)` `...` `return ...` `endfunction`	`function squared(number) squared = number^2 return squared endfunction`
Calling a function	`function(parameters)`	`print(squared(4)) newValue = squared(4)` Note: Function returns should be stored in a variable if needed for later use in a program.

Random Numbers

Concept	Keyword(s) / Symbols	Example
Random numbers	`random(..., ...)`	`myVariable = random(1,6) // Creates a random integer between 1 and 6 inclusive. myVariable = random(-1.0,10.0) // Creates a random real number between -1.0 and 10.0 inclusive.`