Converting File Data Into Double

I am using files to store some numbers in my program. I am storing a string on one line and then a number on another and it repeats (so i've got a client/number sort of system). I can use getline to get that information out of the file but I can't use the number. I need to be able to perform addition and subtraction on the numer... how can I do this?

Also, is there a way to edit a specific part of a file (ie. alter the number and leave the rest as is?).

I am using Borland C++ Builder 5:

Thanks for any help you can provide -
retretret

Read every other line into a double rather than a string.

//get text
in.getline(text,sizeof(text));
//get double
in >> d;

>Also, is there a way to edit a specific part of a file (ie. alter the number and leave the rest as is?).

You could read the whole file into an array of string/double structs, change the ones you want and then write them all back out to file.