Converting binary to Decimal

I need to write a program that converts a 4-Bit Binary number to a decimal and reverse. How can i write a function that converts 4-bit binary to decimal and decimal to binary? What way can i check that the input is actually binary?

Answer 1

[Walter Roberson]

How exactly is the binary number represented?

Answer 2

[Michael Finch]

Right now i have dialog box that ask the user for what conversion method they want. I need to set up a function that checks the number to make sure it is either 4-bit binary or a decimal. I have to verify the input as not exceeding four digits in case of change from binary to decimal, or exceeding two digits in the reverse operation. I have also to verify the input from the user if it is something other than B or D for the operation needed.

[John D'Errico]

So, you know what you need to do. It is time to start writing.

[Michael Finch]

I just don't seem to understand how to change the decimal to binary and binary to decimal. How can i check that the input was actually a 4-bit binary?

[Walter Roberson]

You wrote, "[...] that checks the number [...]"

*What* number? How *exactly* is that number represented?