In linux, these libraries are present in the root folder under usr/include.
You can see them by typing the following in the terminal:
The path for including these files are defined in the gcc itself.
If you use a local header file (for example, create your own) then you have to specify their path if they are in a different folder or just mention their names, if they are in the same folder and you use " " instead of < >
For example, lets say your working directory is foo and it has a local header file foo.h and there is another folder bar inside foo which has a header file bar.h. To include foo.h and bar.h, we write
About the update50, it should be a script in a scripting language like bash or an executable like we generate after the make command, whose path is include in the PATH environment variable of the appliance so that it can be run directly. The script or executable will be having commands which fetch the updates from CS50's server and apply it to the installation.
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