Answer:

The previous branch instructions compare the bit patterns in two registers:

beq  u,v,addr   # Branch if register $u == register $v
                # A branch delay slot follows the instruction.

bne  u,v,addr   # Branch if register $u != register $v
                # A branch delay slot follows the instruction.

Nothing is assumed about what the bit patterns represent. The processor can easily determine if two patterns are the same, or not, no matter how the patterns are being used.

Branch on Less than Zero,
Branch on Greater than Zero

MIPS has several ways to implement relational operators. Here are two more conditional branch instructions. These instructions compare the contents of a register to zero. The register's contents is assumed to be in two's complement representation.

bltz   s,label        #  Branch if the two's comp. integer
                      #  in register s is < 0
                      #  A branch delay slot follows the instruction.

bgez   s,label        #  Branch if the two's comp. integer
                      #  in register s is >= 0
                      #  A branch delay slot follows the instruction.

The first instruction branches if the integer is strictly less than zero. The other branches if the integer is greater than or equal to zero.

Both of these instructions are followed by a branch delay slot. This means that the instruction in that slot will always execute, and the branch (if it happens) will not happen until after that instruction finishes.

QUESTION 2:

Here is a statement in C (or in Java):

if ( !( a < 0 ) ) { ... }

Rewrite it without using the not operator (the !).

if ( a  0  ) { ... }

Answer:

Branch on Less than Zero, Branch on Greater than Zero

QUESTION 2:

Branch on Less than Zero,
Branch on Greater than Zero