SLR 23 - PROGRAMMING TECHNIQUES

Question 1

What are the 3 programming constructs?

Answer 1

• sequence
• selection
• iteration

Question 2

Give an example of each programming construct

Answer 2

• sequence:
  a = 5
  b = 6
  c = a x b
  print(c x 2)
• selection:
  a = 5
  b = 6
  if a > 0:
  print(a x b)
  else:
  print(“a = 0”)
• iteration:
  a = 5
  while a > 0:
  a = a -1

Question 3

What is recursion?

Answer 3

a programming subroutine where a section of code calls itself until a base case is met

Question 4

What are the 3 conditions for a recursive statement?

Answer 4

• contains a stopping condition (base case)
• for any input value other than the stopping condition, the subroutine should call itself (recursion)
• the stopping condition should be reachable within a finite number of times

Question 5

Which is more efficient in terms of memory usage (recursion/iteration) and why?

Answer 5

• iteration
• recursion is not very memory-efficient. Every time a recursive function calls itself, the processor needs to remember where it was before it jumps to the new copy so it knows where to return later​
• the processor also needs to remember the values of all the previous variables, as they are local to those copies of the recursive function – this is done using stacks, which takes up space in memory

Question 6

What is a global variable?

Answer 6

a variable that is:
- “typically” declared at at the top of a program outside of any subroutine
- accessible throughout the program
- created when the program starts
- destroyed when the program ends

Question 7

What is a local variable?

Answer 7

a variable that is:
- declared inside a subroutine
- only accessible by that subroutine
- created when the subroutine is called
- destroyed when the subroutine ends

Question 8

Why is use of global variables generally considered poor programming practice?

Answer 8

excessive, unnecessary use of global variables can make programs hard to test, debug and maintain

Question 9

What is modularity?

Answer 9

• the concept of breaking down a large program/problem down into smaller chunks
• the goal is to design a program in such a way that each module carries out a single, specific task
• modules may be referred to by different names:​
  
  • subroutines​
  • procedures​
  • functions​
  • methods​

Question 10

What is a procedure?

Answer 10

a subroutine that takes in zero, one or more parameters and performs a set task

Question 11

What is a function?

Answer 11

a subroutine that takes in zero, one or more parameters and performs a set task and returns a value

Question 12

What are the 2 methods of passing data into a subroutine?

Answer 12

• passing by value (byVal)
• passing by reference (byRef)

Question 13

What does passing a parameter by reference mean?

Answer 13

passing the address or pointer of the required value into a procedure

Question 14

What does passing a parameter by value mean?

Answer 14

creating a temporary local copy of the actual value of a variable and passing it into the procedure