UMBC CMSC 313, Computer Organization & Assembly Language, Fall 2003

Project 4: C Functions

Due:

Objective

Assignment

1. Convert the program into one that follows the C function call convention, so it may be called from a C program. Your program should work with the following function prototype: void report (void *, unsigned int) ; The intention here is that the first parameter is a pointer to the records array and the second parameter has the number of items in that array.

2. Modify your program so it uses the strncmp() function from the C library to compare the nicknames of two records. The function prototype of strncmp()is: int strncmp(const char *s1, const char *s2, size_t n) ; The function returns an integer less than, equal to, or greater than zero if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match, or be greater than s2.

3. Modify your program so that it prints out the entire record (not just the realname field) of the record with the least number of points and the record with the alphabetically first nickname. You must use the printf()function from the C library to produce this output. The output of your program would look something like: Lowest Points: James Pressman (jamieboy) Alignment: Lawful Neutral Role: Fighter Points: 57 Level: 1 First Nickname: Dan Gannett (danmeister) Alignment: True Neutral Role: Ranger Points: 7502 Level: 3

Implementation Notes

• Documentation for the printf() and strncmp() functions are available on the Unix system by typing man -S 3 printf and man -S 3 strncmp.
• Note that the strncmp() function takes 3 parameters, not 2. It is good programming practice to use strncmp() instead of strcmp() since this prevents runaway loops if the strings are not properly null terminated. The third argument should be 16, the length of the nickname field.
• As in Project 3, you must also make your own test cases. The example in records2.c does not fully exercise your program. As before, your program will be graded based upon other test cases. If you have good examples in Project 3, you can just reuse those.
• Use gcc to link and load your assembly language program with the C program. This way, gcc will call ld with the appropriate options: nasm -f elf report2.asm gcc records2.c report2.o
• Notes on the C function call conventions are available on the web: http://userpages.cs.umbc.edu/chang/cs313.f03/stack.shtml Your program should be reasonably robust and report errors encountered (e.g., empty array) rather than crashing.

Turning in your program

Use the UNIX submit command on the GL system to turn in your project. You should submit at least 4 files: your assembly language program, at least 2 of your own test cases and a typescript file of sample runs of your program. The class name for submit is cs313_0101, cs313_0102 or cs313_0103 for respectively sections 0101 (Chang), 0201 (Patel & Bourner) or 0301 (Macneil). The name of the assignment name is proj4. The UNIX command to do this should look something like: