Programming fundamentals

Question 1

What are the two types of development approaches covered in the course?

Answer 1

1. Waterfall - formal, structured, all steps covered sequentially.
2. Agile - responsive to changing requirements, involves regularly releasing working versions and gaining appropriate feedback.

Question 2

What are some methods for determining the needs of a software project?

Answer 2

1. Surveys to users and management
2. Formal business analysis (this is the role of a systems analyst)
3. Obvservation of users and current practices
4. Interviews with users and management

Question 3

What is the difference between needs and requirements?

Answer 3

Needs are general in nature, while requirements are more specific and should be verifiable, so that the final product can be tested against these requirements.

Question 4

Compare and contrast functional and non-functional specifications

Answer 4

Functional specifications refer to what the system will do, including performance and compatibility.

Non-functional specifications can be considered from the developer’s and user’s perspective and include various aspects like documentation, project management, social and ethical considerations and user interface/experience.

Question 5

What does the Integration stage refer to in the software development cycle?

Answer 5

Integration involves adding the new code in to the new system. Part of this process will involve the code being reviewed and tested to ensure compatibility with any existing code and other systems.

Code versioning systems like Git and the website GitHub allow developers to collaborate on coding project simultaneously.

Question 6

What testing is required after a project has been integrated?

Answer 6

• Volume testing - to check whether the system can handle many requests.
• Transaction types - to simulate real-world usage by using a mixture of different transation types.
• Response times - to check whether the system processes data and responds to user interaction in a reasonable amount of time.

Question 7

What does the Installation phase of the software development cycle refer to?

Answer 7

How the new software system will be adopted by users, either as a new system or as a replacement for an existing system. This involves:
* Training new users in the operation and processes associated with the system.
* Transitioning to the new system, as it may not be feasible to simply switch off the old system and start using the new one.

Question 8

What activities are included in the maintenance stage of software development?

Answer 8

• Fixing bugs
• Adding new features
• Updating the user interface
• Supporting new hardware or software

Question 9

What are the 4 main data types used in programming?

Answer 9

1. String
2. Boolean
3. Integer
4. Real (decimals)

Note that the syllabus also includes:
* Date and time - these are handled by dedicated libraries.
* Single precision floating point - this is a specific way to represent real numbers.

Question 10

What are the 3 types of errors in programming?

Answer 10

1. Syntax error - using incorrect instructions and formatting.
2. Runtime error - occur during execution and results from an illegal operation
3. Logic error - a result of code that does not correctly solve the problem.

Question 11

What is the process of converting binary numbers to their decimal equivalents?

Answer 11

Determine the place value of each bit (as a power of 2) and then sum all values

Question 12

What is the process of converting a decimal number to its binary equivalent?

Answer 12

Moving from left to right, “fill up” the binary values as much as possible for each place value.

Question 13

How many unique values can be stored in a byte?

Answer 13

• A byte is 8 bits, so 2 × 2 × 2 × … = 2⁸ = 256 unique values.
• For an unsigned integer, theses are the numbers fom 0 to 255 inclusive.

Question 14

How does the hexadecimal number system work?

Answer 14

• Hexadecimal is base-16, which means it has the digits 0-9 and then continues from A to F, before “rolling over” to 10.
• The place value of a hexadecimal number is a power of 16.

Question 15

What is the process of converting a binary number to its hexadecimal equivalent?

Answer 15

Each group of 4 bits corresponds to a single hexadecimal digit, so just join them together.

Question 16

How does the 2s complement system represent negative numbers?

Answer 16

• The highest bit of the number takes on a negative value.
• This means that the range of values a signed byte can take on is -128 to 127 inclusive.

Question 17

How does the ASCII system work to represent characters?

Answer 17

• Each character is represented by 7 bits, resulting in 2⁷ = 128 possible characters.
• Some of these characters are non-printable “control characters”.

Question 18

How does the Unicode system work to represent characters?

Answer 18

Unicode uses a variable number of bits for each character, allowing it to represent a huge number of characters (≈150 000).

Question 19

How do bicimals (“binary decimals”) represent non-integer values?

Answer 19

Just like the decimal number system, every value after the decimal point (more generally called the radix point) is a decreasing power of two.

Question 20

How do most computers internally represent time?

Answer 20

As the number of seconds since the Unix epoch (1/1/1970).

You don’t need to know the exact date of the epoch.

Question 21

In the IEEE754 system for representing floating point numbers:
1. The first bit represents the sign
2. The next 8 bit represent the exponent, biased by 127
3. The remaining bits represent the mantissa.

Explain each of these aspects in further detail.

Answer 21

1. If the first bit is 1, the number is negative.
2. The encoded exponent is an unsigned byte - the true exponent is found by subtracting 127 from this number.
3. The mantissa is “1.” followed by the bits in the mantissa.

See example attached.

Question 22

What are the 5 flowchart symbols?

Answer 22

1. Terminator (begin/end) - rounded rectangle
2. Process - rectangle
3. Decision - diamond
4. Input/output - parallelogram
5. Subroutine - rectangle with tracks (“doubles tennis court”)

Question 23

Identify two reasons why pseudocode and flowcharts might be used to represent algorithms instead of simply coding the solution.

Answer 23

1. The algorithm might be easier to understand since pseudocode rules are not as strict as programming languages, and flowcharts show a more visual representation of program flow.
2. The algorithm might need to be implemented in different languages, or the developer might not know ahead of time which language it is going to be implemented in.

Question 24

What are the 4 control structures, used to control program flow.

Answer 24

1. Sequence
2. Decision (branching)
3. Looping (iteration)
4. Subroutines (functions)

Question 25

What is the main way that control structures in pseudocode differ from their implementation in Python?

Answer 25

Both pseudocode and Python use similar keywords for many control structures (e.g. if, else and while). However, pseudocode control structures come in pairs (opening and closing) while Python relies on indentation to indicate the end of a control structure.

Question 26

How are binary decisions represented in pseudocode and flowcharts?

Answer 26

Using keywords IF, ELSE and ENDIF

Question 27

What are the two ways that multiway decisions are represented in pseudocode and flowcharts?

Answer 27

1. Using IF, ELSE IFs, and ENDIF
2. Using CASEWHERE and END CASE.

Question 28

What are the two types of conditional loops in pseudocode and flowcharts?

Answer 28

1. Pre-test loop
2. Post-test loop

Question 29

How do counting loops work in pseudocode and how can they be implemented using flowcharts?

Answer 29

Using the for keyword, but not in the same way as in Python.

Question 30

What is a subroutine?

Answer 30

A named block of code that performs a particular operation. Might also be referred to as a subprogram, procedure or function.

Subroutines might use:
* parameters - information passed to the subroutine.
* return values - information passed back to the calling code.

Question 31

Why are subroutines used in code?

Answer 31

1. For re-use: a subroutine can be called multiple times, often by different parts of the program.
2. For more modular code: assisting with testing and maintaining.

Question 32

Compare and contrast the array and record data structures.

Answer 32

Arrays
* Items are accessed/modified using numerical indexes.
* In pseudocode, round brackets are used with indexes starting at 1.

Records
* Each item is associated with a key.
* “Dot-notation” is used to access/modify values.

In Python, arrays are implemented with the list data type and records with the dictionary data data type.

Question 33

Write a subroutine in pseudocode to print out all items in an array called Names.

Answer 33

This highlights that a counting loop should be used (or a while loop with extra steps), that indexes start at 1, and that the length of an array is not found with a dedicated function like len() in Python.

Question 34

Write a subroutine in pseudocode to print out all values in a record.

Answer 34

Trick question! There is no way to do this in pseudocode, you need to know each individual key to access the corresponding value (using “dot-notation”).

Question 35

What is a structure chart used for?

Answer 35

A structure chart is used to model the hierarchy of modules/subroutines or processes within a system (from top-down), together with the movement of data between subroutines and the order of their execution (from left to right).

Question 36

What symbols are used in a structure chart?

Answer 36

Question 37

What is a desk check?

Answer 37

A manual process to track the values of variables and output through the execution of an algorithm. It is set out as a table with a column for each variable. Each time a variable’s value is modified, its new value is updated in the table.

Conditions and their results are also optional columns in the table and may assist in understanding algorithms with complex conditions (e.g. in loops).

Question 38

What are boundary values?

Answer 38

Boundary values are on the limit of comparisons in code. It is essential to include boundary values when testing algorithms.

Question 39

What is path coverage?

Answer 39

Refers to choosing test data that ensure that all pathways through an algorithm are followed.

Question 40

What test data should be chosen when testing algorithms?

Answer 40

• Above and below boundary values
• Boundary values
• Unexpected inputs

Question 41

What is recursion?

Answer 41

A programming technique where a function calls itself. It is often used in backtracking and divide-and-conquer approaches, and is a key component in functional programming.

Question 42

What is backtracking?

Answer 42

A problem solving technique that involves systematically exploring different options to solve a problem.

Two examples investigated in class were the N-queens problem and the Sudoku puzzle.

Question 43

What is the divide and conquer approach?

Answer 43

A problem solving approach that consists of the following 3 stages:
1. Progressively breaks down a complex problem into smaller, more manageable subproblems.
2. Solves each of these subproblems independently.
3. Combines the subsolutions to obtain the final solution.

In class, we looked at the Merge sort algorithm as an example of a divide and conquer approach.

Question 44

What are the key aspects of each of the 4 programming paradigms covered in class?

Answer 44

1. Imperative - variables and functions are separate.
2. Object-oriented - functionality and data are combined into objects.
3. Functional - Only pure functions are used (no side effects), new variables can be created but not changed.
4. Logic - data is represented as facts and rules using formal logic which can then be queried.