Make, install, executing a program

Question

I have been a CS student for a while and it seems like I (or many of my friends) never understood what's happening behind the scene when it terms to make, install etc.

Correct me but is make a way to compile a set of files?

what is it mean by "installing a program to a computer" like on windows because when I am coding in different languages such as java or perl, we dont install what we wrote. we would compile (if not, interpret language) and just run it. So, why are programs such as Skype needs to be "installed"?

Can anyone clarify this? I feel like this is something i need to know as a programmer.

Answer 1

Make is a build system

Make is a build system which is simply a way to script the steps needed to compile a program. Make specifically can be used with anything, but is usually used to compile C or C++ programs. It simplifies and creates a standard way for programmers to script the preparation of their program, so that it can be built and installed with ease

Why a build system

You see, if your program is a simple one source file program, then using make might be an overkill, as compiling the simplest c program is as simple as

gcc simpleprogram.c -o simpleprogram.out

However, as the size of the software grows, the complexity of it grows, and the complexity of how it needs to be built grows. For example, you may want to determine which version of each library is installed in the computer which you are compiling in, you may want to run some tests after compiling your program to determine it is working correctly, or you may want to automatically download some dependencies your program has.

Most software built need a mixture of these tasks eventually. So, instead of reinventing the wheel, they use a build system which allow scripting this. If you are familiar with Java (which you mentioned) a build system comparable to make, but used in the java world is Apache Ant.

Why install

Well, lets assume that you used the "make" command but not "make install". The "make" command is usually used to just to prepare the program for compilation, and the compile it. However, once your program is compiled, all you have is an executable in the directory in which you compiled the program in. The program, its documentation, and it's configuration files haven't been put in the appropriate directories needed for all users to use it. That's what "make install" is for. Make install takes all the files associated with the program you just compiled, and puts said files in the appropriate directories, so that it becomes available to everyone, and so that each component is in the expected directory according to your operating system.

Answer 2

1. make is a bit of software that reduces the amount of code that needs to be compiled - it compares modification times of the source code with the target. If the code has changed a compile is done to construct the target otherwise you can skip that step.

2. Installing software is placing the executables/configuration files into the right places - perhaps constructing some files along the way. E.g. usernames in your skype example