2.1.2 thinking ahead

Question 1

what is the purpose of thinking ahead?

Answer 1

to make programs easy and intuitive for users to use.

Question 2

define inputs

Answer 2

any data that is required to solve a problem, usually entered into the system by the user

Question 3

define outputs

Answer 3

the results that are passed back once the inputs have been processed and the problem solved

Question 4

what 3 considerations do programmers need to make regarding inputs and outputs when thinking ahead?

Answer 4

method of input/output, data structures used, data types used, order of data

Question 5

what are preconditions?

Answer 5

requirements which must be met before a program can be executed

Question 6

where can preconditions be defined?

Answer 6

within the code or within documentation

Question 7

give an example where preconditions are required

Answer 7

stack functions and factorial functions

Question 8

state 2 advantages of including preconditions within the documentation accompanying a subroutine

Answer 8

reduces the length of the program, reduces the complexity of the program, saves time needed to debug and maintain a longer program, makes subroutine more reusable

Question 9

define caching

Answer 9

the process of storing instructions or values in cache memory after they have been used, as they may be used again

Question 10

how is caching used in storing web pages

Answer 10

web pages that a user frequently accesses are cached, so the next time one of these pages in accessed, content can be loaded without any delay

Question 11

what are the advantages of caching web pages?

Answer 11

content can be loaded without delay, images and text do not have to be downloaded again multiple times, frees bandwidth for other tasks on a network, less time is spend waiting

Question 12

what is the name given to the technique in which instructions are fetched based on algorithms which predict which instructions are likely to soon be used?

Answer 12

prefetching

Question 13

give a limitation of caching

Answer 13

accuracy of the algorithms used, effectiveness of algorithm in managing the cache, size of the cache

Question 14

give 3 advantages of suing reusable program components

Answer 14

more reliable than new components as they have already been tested, as developing from scratch is not required this saves time money and resources

Question 15

give 2 examples of reusable program components

Answer 15

abstract data structures, classes, subroutines