QUICK REFERENCE:

If you want to convert the number 101001 from binary to decimal, do the following:

./qbc 2 10
101001=
^^^^^^^
101001=41

Where the underlined text represents input. Here are some sample runs:
(the underline strings are inputs)

./qbc 2 10
10010101011=
^^^^^^^^^^^^
10010101011=1195
11010, 101 +=
^^^^^^^^^^^^^
11010,101+=31

./qbc 10 16
234 =
^^^^^
234=EA
34532, 323 -=
^^^^^^^^^^^^^
34532,323-=85A1

./qbc R U
CONFUSED=
^^^^^^^^^
55F6KI6=2N01RFF

VERY, CONFUSED x=
^^^^^^^^^^^^^^^^^
14F17,55F6KI6x=243463C

./qbc 3 9
2ABC, 23 -= 23A, 34 += ASDF=
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
21000,100-=220
1101,111+=55
210100=710

As you can see from these sample runs, a case ends when the return button is hit, and there's already an '=' sign inputed. White spaces, tabs, and newline characters are ingnored (except for a newline right after the '=' sign, which signals end of input).

The program is terminated when EOF is inputed (ctrl + d).

USER GUIDE:

Accepted bases: 0-9A-Z (case sensitive) Accepted digits: 0-9A-Z

Operations:
+ <-- adding
- <-- substracting
/ <-- division
x <-- multiplication