3.2

Question 1

3.2.1 operating system (user management)

Answer 1

• provides a user interface to enable users to interact with the computer.

access control: the OS uses log in name and passwords and or some form of biometric identification to authenticate users and control who can log in.

file permissions: control who can do what with each file
(read, write, execute, delete)

Question 2

3.2.1 Main tasks

Answer 2

process management: overseeing the execution of programs by the CPU and allocating each of them a share of main memory and CPU time.

File management: organising and keeping track of the contents of secondary storage, managing files and folders and using permissions to control user access to programs and files.

user management: providing a user interface to enable users to interact with the computer

peripheral management: communicating with device drivers to control peripheral devices

Question 3

3.2.2 Data compression

purpose and how it works

Answer 3

purpose
to reduce the size of a file so that it takes up less space in secondary storage and is quicker to transfer across networks

how it works
it repackages (lossless) or removes (lossy) some of the files data to reduce its size.

Question 4

3.2.3 audit trail

Answer 4

what is it:

• helps improve accountability
• by keeping track of who made what changes and when during the development process.
• if a problem is discovered, it can be tracked back to its source and the code rolled back to a version before the flow was introduced.

version control software

• -> often used alongside audit trails, especially when a team of programmers is working on a large program.
• it uses a database to keep track of every modification to the code.
• if a mistake is made, programmers can revert to an earlier version

Question 5

3.2.3 three things programmer can do to make their programs robust?

Answer 5

adhere to good programming practises

carry out regular code reviews

keep an audit trail

Question 6

3.2.3 bad programming practises:

Answer 6

1) poor planning that does not take account of potential security issues
2) using a quick fix rather than taking time to solve a problem properly
3) poorly structured code that does not here to agreed standards.
4) insufficient testing

Question 7

3.2.3 four things to look for in a code review?

Answer 7

errors in code

code inefficiencies

bad programming practises

requirements are fully implemented

Question 8

3.2.3 code reviews

how it works:

Answer 8

• -> carried out by other programmers or by specialised software.
• -> that checks the code to make sure it meets a pre-defined set of rules
• -> detect bugs and security issues
• -> may suggest ways to fix them

Question 9

3.2.3 code reviews : purpose

Answer 9

purpose to a code review is:

• to check that software adheres to agrees standards.
• to find any instances of insufficient code
• to identify potential vulnerabilities