2.2.1 Programming techniques

Question 1

What’s a…

Programming Construct purpose?

Answer 1

Simplifies problem = easy to understand & program.

Question 2

What’s…

4 Programming Constructs

Structured programming

Answer 2

1. Sequence
2. Selection
3. Iteration
4. Recursion

Recursion is a type of iteration

Question 3

What’s…

Sequential programming?

Programming construct (1/4)

Answer 3

Code executed:

• line-by-line
• top to bottom

Question 4

What’s…

Selection?

Programming construct (2/4)

Answer 4

Code runs if specific condition met.

• Using IF statements.

Also known as ‘Branching’

Question 5

What’s…

Iterative programming

Programming construct (3/4)

Answer 5

Code executed X no. of times or while condition met.

Uses FOR, WHILE or REPEAT UNTIL loops.

Question 6

How’s…

Iteration controlled?

Answer 6

• Count-controlled
• Condition-controlled

Question 7

What’s a…

Count-controlled loop?

Iterative programming

How programmed?

Answer 7

Repeated X no. of times.

for i in range (0,10):
— print i
next i

Question 8

What’s…

Condition-controlled loop?

How programmed?

Answer 8

Continues until a condition met.

while i <= 20:
— print “Not true”;
— i=i+1
endwhile

Question 9

What’s…

Recursion?

Programming construct (4/4)

What’s stopping condition?

Answer 9

Subroutine calls itself during its execution.

Condition met = recursion stops.

Question 10

Why use…

Recursion over Iteration?

Answer 10

• Suits certain problems.
• More easily expressed.

Both produce same result

Question 11

What’s…

Recursion’s main advantage?

Why need to clearly defined?

Answer 11

Uses fewer lines of code = less errors.

NB: Not all problems

Reach stopping condition after a finite no. of function calls.

Question 12

How’s…

Recursion programmed?

Answer 12

function factorial(number)
— if number == 0 or 1:
—— return 1
— else:
—— return number * factorial(number - 1);
— endif
end function

Question 13

What’s a…

Stack frame?

Recursive programming

When?

Answer 13

Stores data within call stack - belonging to subroutine:

• Parameters
• Local variables
• Return addresses

Each time fuction calls itself

Question 14

What’s a…

Call Stack?

Recursive programming

Answer 14

Data structure storing:

• Parameters
• Local variables
• Return addresses

From currently running subroutines.

Question 15

When does…

Subroutine unwind?

Recursive programming

Answer 15

When base case/stopping condition reached

Finite no. of stack frames are created.

Question 16

What’s…

Recusion disadvantages?

Recursive programming

Answer 16

• Inefficient use of memory
• Risk of stack overflow
• Difficult to trace

Question 17

What’s…

Stack overflow?

Recursive programming

Answer 17

Subroutine calls itself too many times = call stack runs out of memory = program crashes.

Question 18

What’s…

Tail recursion?

Answer 18

More efficient = use less stack space.

Question 19

What’s…

Scope?

What’s 2 types?

Answer 19

Section of code where variable = available.

1. Global
2. Local

Question 20

What’s a…

Local variable?

Answer 20

• Limited scope
• Only accessible in block of code where defined.

diff subrouines with same local variable name != effect others

Question 21

What’s…

Local variables benefits?

Answer 21

• Good programming practice.
• Subroutines self-contained.
• Not affected by code outside subroutine.
• Less memory as deleted after subroutine use.

Question 22

What’s…

Global variables?

Answer 22

• Wide scope
• Accessable across whole program.

Variables in main body = automatically global.

Question 23

What’s…

Global variables negatives?

Positives?

Answer 23

• Unintentionally overwritten & edited
• Require more memory as not deleted until program terminates

• useful for values used by multiple parts of program

Question 24

What’s…

Modular programming?

Answer 24

Technique splits large, complex programs –> smaller, self-contained modules.

Question 25

# What's... **Modular** programming's **advantages**?

Answer 25

* Easier to **understand** & approach problems. * Easier to **divide** tasks & manage * **Simplifies** testing & maintenance (components dealt individually). * Improves **reusability** of components (tested module can be reused).

Question 26

# What's... **Top-down approach**? | Modular programming

Answer 26

* Technique to **modularise** programs. * problem **continually split** --> sub problems. (until all = individual **blackbox** performs certain task) | Also known as **stepwise refinement**.

Question 27

# What's a... Procedure? | Subroutines

Answer 27

* Named block of code performs specific task. * Don't need to return value or can return multiple values * Procedures are typically given data as parameters for manipulation

Question 28

# What's a... Function? | Subroutines

Answer 28

* Named blocks of code performing specific task. * Must return single value * Commonly use local variables .

Question 29

# What's... Parameter? | Subroutines

Answer 29

Value passed into a subroutine.

Question 30

# How are... Parameters passed into a subroutine?

Answer 30

* By value * By reference

Question 31

# What happends when... Parameter passed by value?

Answer 31

effectively treated as a local variable ; a copy of the value is passed to the subroutine and discarded at the end therefore its value outside of the subroutine will not be affected.

Question 32

# What happends when... Parameter passed by reference?

Answer 32

Passing by reference means that the address of the parameter is given to the subroutine, so the value of the parameter will be updated at the given address.

Question 33

# What's... IDE? | Integrated Development Environment ## Footnote *Examples?*

Answer 33

a program which provides a s et of tools to make it easier for programmers to write, develop and debug code . ## Footnote *PyCharm, Eclipse, IDLE and Microsoft Visual Studio.*

Question 34

# What's... 5 common IDE features?

Answer 34

1. Stepping 2. Variable watch 3. Breakpoint 4. Source code editor 5. Debugging tools

Question 35

# What's... Stepping? | IDE features (1/5)

Answer 35

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

Question 36

# What's... Variable watch? | IDE features (2/5)

Answer 36

Sometimes used to pinpoint errors, this is a useful feature to observe how the contents of a variable change in real-time through the execution of a program.

Question 37

# What's... Breakpoint? | IDE features (3/5)

Answer 37

IDEs allow users to set a point in the program at which the program will stop. This can either be based on a condition or set to occur at a specific line. This can help to pinpoint where an error is occurring.

Question 38

# What's... Source code editor? | IDE features (4/5)

Answer 38

The editor aims to make the coding process easier by providing features such as autocompletion of words, indentation , syntax highlighting and automatic bracket completion.

Question 39

# What's... Debugging tools? | IDE features (5/5)

Answer 39

Some IDEs also provide run-time detection of error s with a guide as to where in the code they are likely to have occurred through line numbers and highlighting.

Question 40

# What's... A class? | Object-oriented programming

Answer 40

a template for an object and defines the state and behaviour of an object .

Question 41

# What's... An attribute? | Object-oriented programming

Answer 41

give an object’s properties .

Question 42

# What's... A Method? | Object-oriented programming

Answer 42

Actions the class can perform.

Question 43

# What's.. An Object?

Answer 43

a particular instance of a class

Question 44

# What's... Instantiation?

Answer 44

a process where classes can be used to create objects

Question 45

# What's... Encapsulation?

Answer 45

attributes are declared as private so can only be altered by public methods. used throughout programming to implement the principle of information hiding.

Question 46

# What's.. Information hiding?

Answer 46

programs are made less complex by protecting data from being accidentally edited by other parts of the program. | Top-down design use encapsulation, as each module is self-contained.