CS382 Solution

CS 382 Computer Architecture

1 Task: Calling Convention
In this task you will practice calling convention and creating procedures. Things can be very tricky in this lab so be careful!
You will write two procedures in assembly: _uppercase() and _toupper() :
char _uppercase(char lower); receives a single character in lower case, convert it to upper case, and return this new character;
int _toupper(char* string); receives the address of a string, and convert all characters to upper case by calling _uppercase() , and return the number of characters converted. Note this function will convert the characters in place: it will replace the lower case in the old string with upper case, instead of creating a new string.
Using the data in the starter code, the program should print the following:

You can assume the source string always contains and only contains alphabetic lowercase letters.
Be Careful...
When loading a character, or a byte, into a register, the instruction is LDRB or LDRSB , and the destination
register is Wt not Xt . This is the same when you are storing a character back: the instructions are STRB and STRSB .
Requirements Note your code is a complete assembly program (not just a sequence of instructions). It should be able to
assemble, link, and execute without error and warnings. When executed, the program must finish without problems. If your code cannot assemble, link, and/or execute, you get no credit;
You must create procedures correctly, meaning following the calling convention discussed in the textbook
and class;
You must not use any C library functions other than printf() . When using printf() , you must use outstr defined in the starter code without changing it;
You must not hard code any length-related variables;
You do not need to write comments on every line, but you’re strongly encouraged to do so;
2 Grading
The task can be very easy without procedure calls, but getting familiar with procedures and calling conventions are important and therefore exactly the purpose of this lab. We take the proper creation of procedures as equally important as getting the correct output on screen.
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The lab will be graded based on a total of 10 points. The following lists deductibles, and the lowest score is 0 – no negative scores:
the code does not assemble, or the program terminates abnormally/unsuccessfully; the code is generated by compiler or AI; the code cannot be explained clearly in person; did not call _uppercase() in _toupper() and/or _toupper() in the main procedure; used other external functions other than printf() ;
-5: did not call printf() in the main procedure to print expected result;
-5: the procedure was not created properly and/or didn’t follow calling convention. -5 points for each of the two procedures;
-5: the procedure did not return any value; -5 points for each of the two procedures;
-5: declared/hardcoded any data that represents the length of the string;
-3: the string is incorrectly modified or not modified at all; -2: the return value is wrong; -1: no pledge and/or name.

Attendance: check off at the end of the lab to get attendance credit.

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