Because reading assembly language programs can be difficult, it is very important when writing assembly language programs to provide explanatory comments in your code. Please do so for this assignment.

1. Write a leaf procedure in MIPS assembly language that calculates the sum total of an array of integers. Your procedure will take two arguments: a pointer to the array of integers will be passed in register $a0, and the length of the array will be passed in register $a1. Your procedure will return the sum of all the elements of the array in register $v0.

Your procedure MUST be named problem1 so that it can be tested easily. We have provided some code that you can use to help out with testing your procedure. You should load 3 files into spim or xspim in order to use our test code: "lib.s", "p1main.s", and the file you create that contains your procedure. Our test code implements a procedure called main, which sets up the appropriate arguments and then calls your procedure problem1. When your procedure returns, then main prints out the value returned by your code. The correct result that our test code should print is 53.

2. Write a leaf procedure in MIPS assembly language that converts a character string of decimal ASCII digits into the integer value represented by the string. For example, the input string "2739" should be converted into the integer 2739. Your procedure will take one argument: a pointer to the null terminated string of ASCII digits in register $a0. Your procedure will return in register $v0 the integer value represented by the string. Your procedure does not need to handle negative numbers. If a non-digit character appears in the string, your procedure should return the value -1 in register $v0. There is a table in Chapter 3 of your book that describes the value associated with each ASCII character.

Your procedure MUST be named problem2 so that it can be tested easily. We have provided some code that you can use to help out with testing your procedure. You should load 3 files into spim or xspim in order to use our test code: "lib.s", "p2main.s", and the file you create that contains your procedure. Our test code implements a procedure called main, which sets up the appropriate arguments and then calls your procedure problem2. When your procedure returns, then main prints out the value returned by your code. The correct result that our test code should print is 36107.

3. (extra credit) Write a leaf procedure in MIPS assembly that determines whether the machine is little or big endian. Your procedure will not take any arguments. Your procedure should return in register $v0 the value 0 if the machine is little endian, and the value 1 if the machine is big endian.

The protocol for testing your procedure is the same as for the previous two questions.

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