CS 60, Fall 2009
Assignment 1

Due: Friday, October 9, 9:00 pm
Worth: 100 homework points

1. Write and test a program called intbase.c to get and display integer values in various bases.
   • Input bases are decimal, octal, and hexadecimal. Output bases are decimal, octal, hexadecimal, and binary.
   • Start with a copy of ~cs60/hw1/intbase.c-skeleton (at CSIL), and mind the comments/instructions in that file.
   • A function to show a menu and get the user's choice, enum choice menu(void), is already provided. Use it, and do not change it.
   • You must implement main, and the five other functions described below, so your program behaves and produces results that exactly match the behavior and results produced by our executable solution (~cs60/hw1/intbase), including all messages. Note that you may not copy the executable solution, but you can run it from its current location - just type its full name to do so, or cd into its directory to run it as usual.
     1. Write the function, int getInteger(void), to get an integer value from the user, and print the value along with a label that indicates the base that was entered (use exactly the same labels printed by our solution). Allow this integer to be entered as a positive or negative decimal, octal (begins with '0'), or hexadecimal (begins with "0x" or "0X") constant. Skip leading white space, then read to the end of the integer. Return 0 if the user enters invalid text.
        Restrictions: you may not use scanf, sscanf, fscanf, atoi, atof, strtol, or any other library function to process the input. Use getchar to get one character at a time.
        Hints:You may use the character functions of <ctype.h>, and you may model your solution after the simpler atoi implementation given in the K&R text on page 61.
     2. Write four functions to print the current value in different bases (as messages that match the ones produced by our solution):
        1. void putDecimal(int value) - to display in base 10.
        2. void putOctal(int value) - to display in base 8.
        3. void putHex(int value) - to display in base 16.
        4. void putBinary(int value) - to display in base 2.
        Restrictions: you may not use printf (or related library functions) to print the value. Use putchar to print the value one character at a time.
        Hints: see itoa and exercise 3-5 on K&R page 64. Our solution includes the itob function described in the exercise (plus reverse from page 62), and we used this function to easily implement all four of these required display functions.
        Note: show negative values with a minus sign in front of the absolute value (i.e., not the "twos complement" values, even for the binary display).
     3. Write main to present the menu and respond to the users choices until the user chooses to quit. Let the initial value be 0, in case the user chooses to display a value before entering one.
     We encourage you to add utility functions as appropriate to simplify your solution, but you must adhere to the restrictions about library functions.
   • Compile and test with gcc at CSIL before turning in. Use the -Wall option, and make sure that not even warning messages are issued:
     
     gcc -Wall -o intbase intbase.c
2. Turn in intbase.c from your CSIL account as follows:
   
   turnin hw1@cs60 intbase.c
   Late projects may not be accepted.

Updated 9/28/09 by C. Michael Costanzo