Question 1

What does Software design and development cover in SQA National 5 Computing Science?

Accepted Answer

It covers the whole job of writing software. The development process has six iterative stages: analysis, design, implementation, testing, documentation and evaluation. Analysis sets the purpose, scope and functional requirements (inputs, processes, outputs). Design uses structure diagrams, flowcharts, pseudocode and wireframes. Implementation uses data types, arrays and computational constructs (operators, selection and iteration). You must know three standard algorithms: input validation, running total and array traversal. Testing uses normal, extreme and exceptional data and finds syntax, execution and logic errors; evaluation judges fitness for purpose, efficiency, robustness and readability. Low-level operations cover representing data in binary.

Question 2

What are the three standard algorithms at National 5?

Accepted Answer

Input validation uses a conditional loop to keep asking until the user enters acceptable data. A running total sets a total to zero before a loop and adds each value inside it. Traversing a one-dimensional array uses a fixed loop to visit every element by its index. All three are reusable patterns built from selection and iteration, and you should be able to write each in a high-level language you have studied.

Question 3

What is the difference between a syntax error, an execution error and a logic error?

Accepted Answer

A syntax error breaks the grammar rules of the language, so the program will not run or translate, for example a missing bracket. An execution (run-time) error happens while the program is running and crashes it, for example dividing by zero. A logic error lets the program run to the end without crashing but produces the wrong result, because the algorithm is wrong, for example using a plus where a minus was needed. The shorthand is: syntax will not run, execution runs then crashes, logic runs but is wrong.

Question 4

How do you convert a denary number to binary at National 5?

Accepted Answer

Write the 8-bit place values 128, 64, 32, 16, 8, 4, 2 and 1, then fit the number into them from the largest down, putting a 1 where the place value fits and subtracting it. For example 75 gives 64 + 8 + 2 + 1, so the bits are 0100 1011. Always check by adding the place values where the bit is 1 back up to confirm they equal the original number.

Question 5

When should you use a fixed loop instead of a conditional loop?

Accepted Answer

Use a fixed (count-controlled) loop when the number of repetitions is known in advance, such as processing every element of an array of known size. Use a conditional (condition-controlled) loop when the number of repetitions is not known beforehand and depends on what happens while the program runs, such as input validation that keeps asking until the user enters a valid value. Choosing the right loop is itself examined.

SQA National 5 Computing Science: a complete overview of Software design and development

The software development process

Analysis

Design

Data types and structures

Computational constructs

Standard algorithms

Testing and evaluation

Low-level operations and data representation

How Software design and development is examined

For the official course specification

Sources & how we know this