Lecture 5

Lecture 5, Thu 07/11

Makefiles, Data Representation

Code from lecture

Made by Jacqui Mai, Professor K, and me.

Positional encoding: binary, hex, decimal
Internal vs. external representation
Conversion between different representations
Key ideas: bits can represent ANYTHING. With n bits we can represent at most 2^N things
Apply above rule to represent characters (ASCII), unicode, colors ….
The data type of a variable determines its representation in memory AND the number of bits used to store each variable

Write test code and actual code side by side- so your implementation is always tested
Start with function stubs
Write the simplest test case and make your code pass that case
Write another test case, expect your code to fail, see it fail, then add code to pass that test case (and the previous one).
With every new test case, we have to make sure that all our previous tests still pass - this is a great way to make sure that things that were working before are not broken by new code!
If we tried to compile any one file (independent of the others), we are likely to get compiler errors and linker errors. You should be able to distinguish between these two types of errors and why they occur. To understand this distinction we need to peek under the hood of the compilation process and the intermediate steps that g++ takes to create an executable (see slides for more information). You will be introduced to object files - a very important concept for later lessons.
We will first try to compile each file separately on the command line using the g++ option -c. For example

g++ -c shapes.cpp

The above command creates the object file shapes.o

We will then look at how to link all the object files into an executable using the -o option as shown below

g++ file1.o file2.o file3.o -o finalexecuatble