Higher – Testing and Documenting Solutions (Revision)

  •  Constructing a Test Plan: A set of test data which has been created to systematically and comprehensively to test the software; makes use of the following test data
    • normal – ensures the program works when used normally
    • extreme – ensures the program works when data is used that is on the boundaries of what is considered normal
    • exceptional – ensures a program can handle situations that it has not been designed to cope with; out with the boundaries
  • Comprehensive Testing: when every aspect of the software is tested
  • Syntax Error: a misspelling of a keyword or mistake in the structure of a program such as missing an ‘end if’
  • Logic Error: program will run but not as the programmer intended it to; for example when calculating the average it should be (a+b)/2 instead of a+b/2
  • Execution Error: an error occurs when the program is run, causing it to crash
  • Dry Runs: manual run through of pseudocode or source code of program, taking notes of the values of variables at various points in the process
  • Trace Tables: similar to the table used during a dry run but is often used to test an algorithm for a specific sub program
  • Breakpoints: a set point in a program where it will stop execution so that the values of variables can be examined

Thank you to C O’Toole & A Madill from Braidhurst High School for allowing me to edit and publish this here.

National 5 – Algorithm Specification (Revision)

Input validation – checking that what is entered by the user is acceptable.

The following program checks that age is a positive number.

1. SEND “Please enter age” TO DISPLAY
3. RECEIVE age FROM (INTEGER) KEYBOARD
4. WHILE age < 0 DO
5.         SEND “re-enter data” TO DISPLAY
6.         RECEIVE age FROM (INTEGER) KEYBOARD
7. END WHILE

Note that acceptable does not mean accurate, just sensible.

Higher – Reading Standard Reference Language

I would like to remind you that there is no requirement to write answers using Standard Reference Language (SRL). The SQA can sometimes refer to Standard Reference Language as “Pseudocode”, however, as I have previously explained this is not the case. Pseudocode is an informal design that explains a programs function using English like structure.

Examples

Read in a number representing a temperature in degrees Celsius and write it out as a value in degrees Fahrenheit. If the Celsius value is c, then the Fahrenheit value, f, is calculated as follows: f = ( 9 / 5 ) * c + 32.

RECEIVE c FROM (INTEGER) KEYBOARD 
DECLARE f INITIALLY ( 9.0 / 5.0 ) * c + 32 
SEND f TO DISPLAY

Read in 10 numbers and write out the average of those numbers.

DECLARE total INITIALLY 0 
DECLARE count INITIALLY 0 
WHILE count < 10 DO 
    RECEIVE nextInput FROM (INTEGER) KEYBOARD 
    SET total TO total + nextInput 
    SET count TO count + 1 
END WHILE 
SEND total / 10.0 TO DISPLAY

When reading SRL start at the top, working down each line. Take a note on scrap paper of the values given to variables. In SRL constructs start with their NAME and finish with an END and their name. Subprograms can either be a PROCEDURE or FUNCTION, these are named and have parameters (arguments) in parenthesises, functions will have one or more RETURN statements.

Tips

  • If you are asked for the results of the program then pay attention to the IF statements to make sure that you branch the program correctly. Check the number of repetitions on loops as well.
  • If you are asked to spot an error in the code it will more than likely be a logical error rather than a syntax error.

There is an online Haggis (SRL) checker here, remember you don’t need to write SRL just read it.

National 5 – Testing and documenting solutions (Revision)

Test Data

For an exam out of 100

  • Normal (data within expected range) – 78, 45,67, 85, 44
  • Extreme (data at limits of expected range)– 0, 100
  • Exceptional (data out with expected range) – -89, bob

Errors

  • Syntax – The rules of the programming language have been broken. E.g. a typing mistake Displya rather than Display
  • Execution – using Average = total / 0 would give an execution error.
  • Logic –will only show up when you run the program. Please see below

counter = 0
while counter < 0:
counter = counter + 1

Readability of code

  • Internal commentary – information about what the program does written by the programmer alongside the actual code. #Green in python.
  • Meaningful identifiers – Calling variable names that mean something length or height rather than L or H
  • Indentation starting parts of the code slightly into the middle of the page making it easier to read.

Higher – Data Types and Structures (Revision)

  • String: text (str)
  • Integer: whole numbers (int)
  • Real: decimal numbers (float)
  • Boolean: one of two possible values e.g. True/False
  • 1-D Arrays: two or more values of the same data type stored in the same construct
  • Records: two or more values of different data types stored in the same construct
  • Sequential Files: text files that can be opened, closed, read from, written to, created or deleted; identified by a path and filename which is treated as a STRING e.g. “n:\myfiles\testfile.txt” would identify the file testfile.txt in the folder n:\myfiles.

 

Thank you to C O’Toole & A Madill from Braidhurst High School for allowing me to publish this here.

National 5 – Data types and structures (Revision)

String – text variable like name
Integer – a whole number used for numberOfPeople or items
Real – contains decimals used for distances or measurements
Graphical objects – pictures
Boolean variables – True or False
One Dimensional (1D) arrays – used for a data structure with many pieces of data all of the same data type, such as a list of names. Pupilname[20]

Higher – Computational Constructs (revision)

  • Parameter passing: used to pass data from one subprogram to another; can either be passed by value (data will not change) or by reference (changes to the data will be made)
  • Variable scope: where a variable can be used in a program; local (only inside the subprogram in which the variable has been created) or global (can be used in any subprogram)
  • Subprograms: named blocks of code which can be run from within another part of the program; often used to break a large program into smaller steps
    • Functions: a type of subprogram used to return a single value eg round, random
    • Procedures: a type of subprogram that will follow a set of given instructions
    • Methods: a function in an object-oriented language that is defined inside a class

Thank you to C O’Toole & A Madill from Braidhurst High School for allowing me to publish this here.

National 5 – Computational Constructs (Revision)

Expressions to assign values to variables

Number=0
Expressions to return values using arithmetic operations (+ – * / ^ mod)

Average=total/5
Execution of lines of code in sequence demonstrating input – process- output

1. SEND “Enter First Number” TO DISPLAY

2. RECEIVE first_number FROM (INTEGER) KEYBOARD [input]

3. SEND “Enter Second Number” TO DISPLAY

4. RECEIVE second_number FROM (INTEGER) KEYBOARD [input]

5. SET total TO first_number + second_number [process]

6. SEND total TO DISPLAY [output]
Expressions to concatenate strings and arrays using the & operator

Bob Smith is an example of concatenation

 

firstName=”Bob”

secondName=”Smith”

print(firstName + secondName)

 

BobSmith
Use of selection constructs including simple and complex conditional statements and logical operators.

This is a simple statement as there is one conditions

1. IF pupil_mark >=50 THEN

2.    SEND pass message TO DISPLAY

3. ELSE

4. SEND fail message TO DISPLAY

5. END IF

 

This is a complex statement as there are two conditions

1. IF pupil_mark >=50 AND assessments_mark = 100 THEN

2.     SEND pass message TO DISPLAY

3. ELSE

4.      SEND fail message TO DISPLAY

5. END IF
Iteration and repetition using fixed and conditional loops

Fixed loop below as it will loop a fixed number of times depending on the users answer

number=int(input(“How many smart phones?”))

total=0.0

for phone in range(number):

                Name=input(“Please enter the name of the smart phone:”)

                cost=float(input(“Please enter the cost of the smart phone:”))

                total=total + cost

print(“Total cost = “,total)

 

Below is a Conditional Loop as it depends whether the user has any money left.

money=int(input(“Please enter your pocket money in £”))

while money>0:

    name=input(“Please enter the name of the CD you want to buy”)

    cost=float(input(“Please enter the cost of the CD”))

    money=money-cost

print(“You have ran out of pocket money”)
Pre-defined functions (with parameters) – round(22.34 ) will round numbers 22.34 becomes 22 or sqrt(4) will get the square root 2, or 9 will become 3.

Higher – Languages and Environments (Revision)

·         Low-level: language that a computer will understand; consists of 0s, 1s; examples include assembly code and machine code

·         High-level: language that a human will understand; use of English words such as repeat, if, loop, put

·         Procedural: code will processed logically and in a set order; passes data from one procedure to another using parameters

·         Declarative: consists of a knowledge base of facts and rules that can be queried

·         Object-Oriented: objects are created using classes that will contain code and data (encapsulation); data associated is known as attributes and its values are known as states; sub-classes can inherit attributes from a pre-defined class

·         Interpreter: takes each line of source code, translates it into machine code then passes it to processor to carry out that instruction; it works its way through the program one line at a time

Advantages Disadvantages
A program will run even if it is not finished No copy of machine code is saved meaning the source code has to be translated every time taking longer
Easy to spot errors during the translation The process of translating the program slows down the running of it
Program will run as soon as the first line is translated You will need to have a translator program or you cannot run it

·         Compiler: reads the source code and translates the entire program into machine code once; machine code then saved and kept and doesn’t need to be further translated before run

Advantages Disadvantages
The machine code is saved so the program only needs to be translated once You have to wait until the code is complete and the errors have been fixed before the translation can be finished and the machine code is run
The user does not need a translator program to run the machine code therefore the program runs quicker Each time the program is changed it needs to be re-translated

Thank you to C O’Toole & A Madill from Braidhurst High School for allowing me to publish this here.

National 5 & Higher Course Content

You have a paper copy of this in your folders but I thought you might want an electronic copy.

The document is divided into

  • Yellow (SDD)
  • Orange (SDD & ISDD)
  • Red (ISDD)

For the exam National 5 pupils could be asked question from National 4 & 5. Higher pupils can be asked about content from all three courses.

TIP: Take a highlighter and mark of areas as you study them, use traffic lights to mark areas you need to come back to.