#Calculator using reverse polish notation

##Accepted input:

• number literals
• +/-*
• =
• quit

##Sample calculation in UPN

• In well-known infix: (2 + 3) * 4
• In UPN: 2 3 + 4 *

##Compilation

• gcc upn_calc.c int_stack.c -o upn_calc

##Sample session:

• ./upn_calc
• Input: 2 [return] 3 [return] + [return] 4 [return] * [return] = [return] quit [return]
• Output: 20