Compilation process
All information inside a system is represented as a bunch of bits [bunch may be underestimating its power].
The very process by which a compiler compiles the code and displays output for languages like C, Java, etc. deals with converting to and from bytes.
Compiler
Now, a compiler is a tool to translate our source code to a sequence of low-level instructions, written in binary. We pass instructions to our computer by translating our program using this tool.
Languages like C, Java, C++, etc. use a compiler. Languages like Python and JavaScript, on the other hand, use an interpreter.
Its finished product is called an executable object program [or simply, file] and is stored as a binary disk file.
To translate a program and execute it, a compiler undergoes the following phases [we use C as an example here] :
Preprocessing phase
In this phase, the program is modified according to the directives issues by a pre-processor, a program that produces output from certain input to be used as input for another program.
Directives are statements that tell the pre-processor to perform an action.
For example, #include <stdio.h> is a directive in C telling the pre-processor to use functions from the header file [a library] called Standard Input / Output.
A library [or in this case, a header file] is a file containing pre-defined functions.
Compilation phase
Now the compiler translates the source file into a text file that contains its Assembly translation. This phase is where most compile-time errors occur.
Assembly phase
After the translation’s done, the assembler [a program that converts Assembly language into binary] translates the text file into an actual binary file and packs it neatly into a relocatable object program [an object file that contains code which can be linked with other files to create an executable object file].
This program is stored as an object file. It contains the binary output, but isn’t executable yet.
Linking phase
Now, the final phase of compilation involves another program called linker merging the necessary files [such as code for library functions used in the program] with the object file.
This creates an executable object file [just executable, please], which is loaded into memory and executed by your system.
This phase is also famous for linker errors that happen when it’s unable to combine the files properly.
Why do we need to understand this?
“Why can’t I just…code? I’ll understand this better!”
If you understand how different statements are dealt by the compiler, and how binary works, you can make your program efficient to handle.
Instead of grouping 4-5 if-else ladders, you’d use a single switch statement.
Instead of using a while(true) loop, you’d switch to a do-while loop.
Overhead [extra time or memory used to achieve a goal] wouldn’t be too much.