For these programming exercises, use only those instructions that have been discussed so far in these notes:
add div mflo slt, slti addi divu mult sltu, sltiu addiu j multu sra addu lb nor srl and lbu or sub andi lh ori subu beq lhu sb sw bgez lui sh xor bltz lw sll xori bne mfhi In the Settings menu of SPIM set Bare Machine ON, Allow Pseudo Instructions OFF, Load Trap File OFF, Delayed Branches ON, Delayed Loads ON, Mapped IO OFF, Quiet OFF.
Run the programs by setting the value of the PC to 0x400000 and then single stepping (pushing F10) or by multiple stepping (push F11 and enter a number of steps). Observing the results in the SPIM window.
Write a program that stores the number 0 in the first
four bytes of the .data section,
then stores the number 1 in the next
four bytes,
then stores the number 2 in the
four bytes after that and so on.
Do this for numbers 0 through 24.
Of course you will do this in a counting loop. The address in the data section is contained in a base register. Increment the base register each time a number is stored.
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A perfect number is an integer whose integer divisors sum up to the number. For example, 6 is perfect because 6 is divided by 1, 2, and 3 and 6 = 1 + 2 + 3. Other perfect numbers are 28 and 496.
Write a program that determines if an integer stored in memory is a perfect number. Set a location in memory to 1 if the number is perfect, to 0 if not.
It would be enormously helpful to first do this by hand with a couple of examples. Then draw a flowchart. Check the flowchart by following it with a few examples. Then write the program.
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This exercise continues exercise 2.
Write a program that searches for perfect numbers. It has an outer loop that counts upward from two to some limit. Each number is tested (as above) to see if it is a perfect number. If it is a perfect number it is stored at a memory location. Store perfect numbers at successive full-word memory locations. Look at exercise 1 for a way to do this.
Again, to save time and effort, create a flowchart first.
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