Programming Techniques

Question 1

Explain the term procedure.

Answer 1

• A block of code/ set of instructions
• Performs a task
• Receives parameter values
• Uses local variables
• May return values

Question 2

Explain how parameters are used.

Answer 2

• Supplied to a procedure or function
• They are used to pass values between functions/procedures
• They are passed by reference or by value
• Uses as a local variable

Question 3

State benefits of using procedures.

Answer 3

• procedures tested separately
• easier to maintain program
• main program is simpler/code is clearly structured
• use of library routines to save time
• code is reusable
• program produced faster/to a higher standard…
• …as procedures may be shared between
  programmers

Question 4

Describe stepwise refinement.

Answer 4

• problem broken into sections…
• which become progressively smaller
• until each section can be written as a single
  procedure/represents one step in the algorithm

Question 5

Explain the term global variable.

Answer 5

• a variable defined at the start of a program
• exists throughout program…
• including functions & procedures
• allows data to be shared by modules
• overridden by local variables with same name

Question 6

Explain the term local variable.

Answer 6

• a variable defined within one module…
• & only accessible in that module
• data is lost when module is completed
• same variable name may be used in different
  modules

Question 7

Discuss the use of functions in developing programs.

Answer 7

• block of code…
• …which performs a single task/calculation…
• returns a single value
• uses local variables

Question 8

Discuss the use of procedures in developing programs.

Answer 8

• block of code…
• …which performs a task
• …which may or may not produce a single value
• uses local variables

Question 9

Discuss the use of stepwise refinement in developing programs.

Answer 9

• breaks a problem into sections…
• …which become progressively smaller…
• …until each module can be written as a single procedure/function
• each module can be tested separately
• library routines can be used

Question 10

What data structure is used to handle procedure calling and parameter passing?

Answer 10

Stack

Question 11

Explain the term parameter.

Answer 11

• (information about) an item of data…
• …supplied to a procedure or function
• may be passed by reference or by value
• used as a local variable

Question 12

State the purpose of of syntax diagrams.

Answer 12

to unambiguously define terms for a computer language

Question 13

What other notation can be used other than syntax diagrams?

Answer 13

Backus-Naur Form

Question 14

State advantages of using reverse polish notation compared with infix algebraic notation.

Answer 14

-any expression can be processed in order (left to right)
- no rules of precedence are needed/no brackets are
needed/unambiguous

Question 15

What tree traversal should be used for reverse polish notation?

Answer 15

post order