Assignment 1, due Jan 28

Part of the homework for 22C:169, Spring 2011
by Douglas W. Jones
THE UNIVERSITY OF IOWA Department of Computer Science

Always, on every assignment, please write your name legibly as it appears on your University ID and on the class list! All assignments will be due at the start of class on the day indicated (usually a Friday), and unless there is what insurance companies call "an act of God" - something outside your control; the only exceptions to this rule will be by advance arrangement.

  1. Find a C compiler, any C or C++ compiler on any computer system. Veryfy that you can actually compile programs under it and that it produces an executable object file that you can find in some file system. Name that compiler and identify the computer system on which it works. (1 point)

  2. Compile and run the C Hello World program from lecture 2. Change the program so that it contains a comment giving your name and so that it outputs your name instead of the string Hello World (see the C style guidelines cited in lecture 2 for a suggested commenting convention). Turn in a legible printed copy of this modified program; it should be much shorter than a page. Note to C++ programmers: Please avoid using C++ comment conventions. (1 point)

  3. Modify the program so that it outputs, in hexadecimal, the address of your string instead of outputting the text of the string. To output the pointer p in hex using C, assuming that pointers are 24 bits (they aren't on any of our machines), use printf("%6x",p) (the 6 is the number of digits per pointer). Again, turn in a legible printed copy of this short program (it ought to fit on the same page as the first one). (1 point)

  4. Figure out how to modify the a.out object file! For example, replace all instances of your name in the object file with a nonsense string of the same length. The worst case solution to this problem would involve writing a little program that reads, modifies and writes the object file, but any of several common UNIX editors can be made to do this. Report on your methodology, giving details of how you did it. (1 point)

  5. Write a C or C++ function that prints out the address of the first local variable in its activation record, in hex, with a main program that demonstrates it. (1 point)