2.2.1 Programming Techniques

Question 1

Sequence

Answer 1

Code is executed line-by-line, from top to bottom

Question 2

Branching (AKA Selection)

Answer 2

A certain block of code is run if a specific condition is met, using IF statements.

Question 3

Iteration

Answer 3

A block of code is executed a certain number of times or while a condition is met. Uses FOR, WHILE or REPEAT UNTIL loops.

Question 4

Count-controlled VS Condition-controlled

Answer 4

Count-controlled: Iteration is repeated a given number of times
Condition-controlled: Iteration continues until a given condition is met.

Question 5

Recursion

Answer 5

A programming construct in which a subroutine calls itself during its execution. This continues until the stopping condition is met.

Question 6

Advantages of recursion

Answer 6

Certain problems can be represented in fewer lines of code, making them less prone to errors.

Question 7

Disadvantages of recursion

Answer 7

• Inefficient use of memory.
• Danger of stack overflow.
• Difficult to trace. This difficulty grows with more function calls.

Question 8

Recursion relies on a stack, in order for it to work. Explain how recursion uses the call stack.

Answer 8

Each time the function calls itself, a new stack frame is created within the call stack.
A finite number of stack frames are created until the base case is reached. The subroutine unwinds, and begins to pop information off the stack

Question 9

What do stack frames contain?

Answer 9

Parameters, local variables and return addresses.

Question 10

Describe stack overflow during recursion

Answer 10

The call stack runs out of memory as a result of the subroutine calling itself too many times, causing the program to crash.

Question 11

What does scope refer to?

Answer 11

The section of code in which the variable is available.

Question 12

Local variables have limited scope. What does this mean?

Answer 12

They can only be accessed within the block of code in which they were defined.

Question 13

Using local variables is considered good programming practice. Why?

Answer 13

It ensures subroutines are self contained, with no danger of variables being affected by code outside the subroutine.

Question 14

Global variables can be accessed across the whole program. What is this useful for?

Answer 14

Values that need to be used by multiple parts of the program.

Question 15

Why are global variables not recommended?

Answer 15

They can be unintentionally overwritten and edited. They also require more memory than local variables.

Question 16

A local variable exists within a subroutine with the same name as a global variable. Which variable takes precedence?

Answer 16

The local variable.

Question 17

Modular programming

Answer 17

A programming technique used to split large complex programs into smaller, self contained modules.

Question 18

Benefits of modularity

Answer 18

Makes problem easier to understand and approach
Makes it easier to divide tasks between a team and manage
Simplifies testing process as individual modules can be tested, improving reusability

Question 19

The top down approach is a popular technique for modularising programs. How does it work?

Answer 19

The problem is continually broken down into subproblems, until each can be represented as an individual blackbox which performs a certain task. This is known as stepwise refinement.

Question 20

Procedure/Function

Answer 20

Named blocks of code that perform a specific task.
Functions return a value, whereas procedures do not.

Question 21

Passing a parameter by value

Answer 21

A copy of the value is passed to the subroutine and discarded at the end.

Question 22

Passing a parameter by reference.

Answer 22

The address of the parameter is given to the subroutine, so the value of the parameter will be updated at the given address.

Question 23

Integrated Development Environment

Answer 23

A program which provides a set of tools to make it easier for programmers to write, develop and debug code.

Question 24

Stepping (IDE Feature)

Answer 24

Allows you to monitor the effect of each individual line of code by executing a single line at a time.

Question 25

Variable watch (IDE Feature)

Answer 25

Used to observe how the contents of a variable change in real-time through the execution of a program.

Question 26

Breakpoint (IDE Feature)

Answer 26

Allows users to set a point in the program at which the program will stop.

Question 27

Source code editor (IDE Feature)

Answer 27

Provides features such as autocompletion, indentation and syntax highlighting to make the coding process easier.