Looking at the task manager, Pelles C only uses 20MB to 25MB of my computer's memory. What a lightweight IDE and that's even with a basic program compiled for debugging. That's tiny for an era where modern desktops have anywhere from 8GB to 64GB of RAM.
PellesC IDE is coded using directly windows API, so there is no bloating code due to glue logic in large runtime libraries (C#, C++, etc.).
Most part of GUI and other functionalities are inside system DLL's (i.e. kernel32.lib, advapi32.lib, user32.lib, etc.) that are already loaded and shared with all programs (even those in C++ or C#, or any other HLL which always depends on the base API). They are simply linked with your C code.