I am wondering if all colleges have the same grading system, i.e. A, AB, B, BC, C, etc or different as in high schools. If different, how do graduate schools evaluate applicants?
Grading systems are completely different. I have actually never heard of the one you mentioned.
Most college grading systems us A,B,C,D,F with +/-, but of course some are different. Look at each college you are interested in.
College transcripts usually have an explanation of the grading system for the particular school on the back or second page. There are usually letter grades, and GPAs.
All colleges are different. Heck, even at colleges there isn’t some universal scale (like 100-90 = A or whatever).
Grad schools evaluate you holistically. They don’t (generally) put your GPA & GRE (or whatever) into a machine and whoever has the highest score “wins.” Especially for PhD programs, a lot of it is based on how your research interests fit with faculty.
Most colleges use A/B/C/D/F letter grades and may or may not use +/-. I’ve never heard of a college having weighted GPA like many high schools do.
The conversion of percentages to letter grades depends on the class. In most of my classes, the percentage cutoffs for different letter grades have been determined by the professor at the end of the class. I attended another university where almost all classes required 93 for an A, but my GPA was a lot higher there somehow.
My large public undergrad didn’t use A/B/whatever… It was 4.0/3.5/3.0/etc
Like I said, it depends on the school.