Using fread to store data into a char buffer

I am working on a project where I need to read data from a binary file. I am trying to store the data into a char buffer. Suppose the binary file consisted of a character, an int and a double what size would the char buffer need to be ? And how would I convert back into int's and doubles ?

I am reading the data into a char buffer because it would improve the speed of my program.

Thanks!

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