The 3 L's

Question 1

What are libraries?

Answer 1

They are ready-compiled and tested programs that can be run when needed.

Question 2

Advantages of Libraries

Answer 2

Any 2 of:

1. Quick and easy to use and hook into your own code
2. Pre-tested, so you can be relatively sure they are already free from errors
3. Pre-compiled, so they are typically optimised to run quickly

Question 3

Disadvantages of libraries

Answer 3

Any 2 of:

1. Adding functionality or making specific tweaks can be difficult
2. Sometimes you are “black-boxed” from the actual implementation
3. You have to trust that the developers will continue to maintain the library

Question 4

What are linkers?

Answer 4

Linkers pull in libraries when needed in a process. There are 2 ways to link libraries into code. Static and Dynamic

Question 5

What is static linking?

Answer 5

All required code from libraries is directly included in the finished machine code

Question 5

What is dynamic linking?

Answer 5

• Compiled versions of libraries are stored on host computer
• Operating system links the required code from the library as the program is running
• While this cuts down the size of compiled machine code, if dynamic libraries ever change, the program may stop; it will be called in the wrong way

Question 6

What is a loader?

Answer 6

A part of the operating system that loads the executable program file (machine code) into memory, ready to run