CODEWITHSUNDEEP
c++compilationmachine-code
ersbygre1
ersbygre1

Reputation: 181

How does compiling C++ code produce machine code?

I'm studying C++ using the website learncpp.com. Chapter 0.5 states that the purpose of a compiler is to translate human-readable source code to machine-readable machine code, consisting of 1's and 0's.

I've written a short hello-world program and used g++ hello-world.cpp to compile it (I'm using macOS). The result is a.out. It does print "Hello World" just fine, however, when I try to look at a.out in vim/less/Atom/..., I don't see 1's and 0', but rather a lot of this:

H�E�H��X�����H�E�H�}���H��X���H9��

Why are the contents of a.out not just 1's and 0's, as would be expected from machine code?

Upvotes: 3

Views: 1004

Answers (1)

joshmeranda
joshmeranda

Reputation: 3251

They are binary bits (1s and 0s) but whatever piece of software you are using to view the file's contents is trying to read them as human readable characters, not as machine code.

If you think about it, everything that you open in a text editor is comprised of binary bits stored on bare metal. Those 1s and 0s can be interpreted in many many different ways, and most text editors will attempt to read them in as characters. Take the character 'A' for example. It's ASCII code is 65 which is 01000001 in binary. When a text editor reads through the file on your computer it is processing those bits as characters rather than machine instructions, and therefore it reads in 8 bits (byte) in the pattern 01000001 it knows that it has just read an 'A'.

This process results in that jumble of symbols you see in the executable file. While some of the content happens to be in the right pattern to make human readable characters, the majority of them will likely be outside of what either the character encoding considers valid or knows how to print, resulting in the '�' that you see.

I won't go into the intricacies of how character encodings work here, but read Character Encodings for Beginners for a bit more info.

Upvotes: 6

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