C Calculator - Reading and Writing from file

Hi,
I am trying to make a calculator that reads an input file like the example below and then outputs to another file like the example. I am trying not to use any string operations like strlen and things like that. Can someone please assist me on how to spilt up the string into it's separates operators and operands.

Input File Example

Quote:

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5*5

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Output File Example

Quote:

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5*5 = 25

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Thanks

Sounds good. Do it!

Can you please assist me on how to spilt up the string into it's separates operators and operands.

I'd start by being clear on the input file format. Are you allowing for multiple digits in a number? Negative numbers? Can there be spaces between operands? What operators are permitted? Can multiple operators be used to create a more complex expression?