6.5: Exercises

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Why do "la label" instructions always need to be translated into 2 lines of pseudo code? What about "lw label" instructions? Explain the similarities and differences in how they are implemented in MARS.

The following table has memory addresses in each row, and columns which represent each of the MIPS boundary types, byte, half word, word, and double word. Put a check mark in the column if the address for that row falls on the boundary type for the column.

Address	Boundary Type
Address	Byte	Half	Word	Double
0x10010011
0x10010100
0x10050108
0x1005010c
0x1005010d
0x1005010e
0x1005010f
0x10070104

The following program fails to load the value 8 into $t0. In fact it creates an exception. Why?

.text
    lui $t0, 1001
    lw $a0, 0($t0)
    li $v0, 1
    syscall
    li $v0, 10
    syscall
.data
    .word 8

Translate the following pseudo code into MIPS assembly to show each of the addressing modes covered in this chapter. Note that variables x and y are static and volatile, so should be stored in data memory. When using register direct access, you do not need to store the variables in memory.
```
main() {
    static volatile int miles = prompt("Enter the number of miles driven: ");
    static volatile int gallons = prompt("Enter the number of gallons used: ");
    static volatile int mpg = miles / gallons;
    output("Your mpg = " + mpg);
}
```