MIPS Items

Question 1

CPU Instruction

Answer 1

binary pattern of 0’s and 1’s.

Question 2

Instruction Set (ISA)

Answer 2

the vocabulary of commands understood by a given architecture

Question 3

CPU arch

Answer 3

collection of general specifications that CPU follows

Question 4

Specification about CPU Architecture

Answer 4

instruction set, number and size of registers, word size, address size and etc.

Question 5

Assembly Language

Answer 5

a symbolic representation of machine instruction
Requires programmer to write one line for every instruction that the computer will follow

Question 6

What are the main properties of assembly languages?

Answer 6

1. closely represent CPU instructions
2. Assembly languages are architecture specific

Question 7

List ex of Assembly Lang

Answer 7

MIPS for some old classic CPUs
x86 for Intel-style CPUs
ARM 8 for smartphone CPUs

Question 8

What are pseudo-instructions

Answer 8

structions do not directly correspond to a single machine instruction in the MIPS instruction set

Question 9

How many general-purpose registers do MIPS CPU have

Answer 9

32 general purpose register
each register is 4 bytes (word)

Question 10

Can a register store nothing at all? Can some bits in a register store nothing at all?

Answer 10

NO a register cannot hold nothing even a pattern of all zero’s is still storing something

Question 11

Name some MIPS general purpose registers.

Answer 11

$s0 - $s7, $t0 - $t7, $zero

Question 12

What is stored in the register $zero? Are we allowed to change it’s content?

Answer 12

Constant value - and you are NOT allowed to change it

Question 13

Immediate value in ADDI

Answer 13

Constant

Question 14

Where is a variable stored?

Answer 14

IN RAM

Question 15

What is loading the register?

Answer 15

Copying word of data from RAM to CPU register

Question 16

SW

Answer 16

Copies the data from a register to memory.

Question 17

Endianess. Big-endian and little-endian.

Answer 17

Computers either use the address of the leftmost or “big end” byte as the word address and those that use the rightmost or “little end” byte. MIPS uses big-endian.

Question 18

What should we do to use the value of a variable?

Answer 18

load it from RAM to register

Question 19

2’s complement representation of signed integers.

Answer 19

PRACTICE

Question 20

Unsigned integer representation.

Answer 20

Practice

Question 21

Know how to determine numeric limits for both 2’s complement and unsigned representations when given the number of bits.

Answer 21

General Range for n-bit Unsigned Integer:
0 - (2^n)-1
ex: 8 bits
0 - 255

2’s Complement:
Minimum value: -2^(n-1)
Maximum Value: 2^(n-1)-1
ex: 8 bits
-128 - 127

Question 22

How do we specify memory address in loading and storing instructions?

Answer 22

offset($baseRegister)

Question 23

What is the difference between lh and lhu, between lb and lbu?

Answer 23

Sign-extends

Question 24

Why we don’t need separate signed and unsigned versions for storing instructions.

Answer 24

copying the bit pattern from a register to a memory location.

Question 25

Converting 2’s Complement to Decimal

Answer 25

1.) Invert the bits
1111 1111 1111 1111 1111 1111 1111 0011
0000 0000 0000 0000 0000 0000 0000 1100
2.) ADD +1
0000 0000 0000 0000 0000 0000 0000 1100
0000 0000 0000 0000 0000 0000 0000 1101
3.) Convert to Decimal
-13

Question 26

Does label exist as a separate item in the compiled program code?

Answer 26

No

Question 27

j instruction. Label

Answer 27

label marks an instruction in the program code

Question 28

What does label turn into in the compiled program code?

Answer 28

it turns to an address of the labeled instruction in RAM

Question 29

Instructions beq and bne

Answer 29

beq register1, register2, L1 if ==
bne register1, register2, L1 if !=

Question 30

What unconditional jumps do you know

Answer 30

J label

Question 31

Instructions slt, slti, sltu, sltiu.

Answer 31

slt $t0, $s3, $s4 $t0 = 1 if $s3 < $s4

slti $t0, $s2, 10 $t0 = 1 if $s2 < 10

sltu (set on less than unsigned)

sltiu (set on less than immediate unsigned)

Question 32

Be able to give an example of two parameters in form of bit patterns that produce different results in slt and sltu.

Answer 32

$t0 = 0xFFFFFFF3 is interpreted as -13
$t1 = 0x00000005 is interpreted as 5
slt $t2, $t0, $t1 # $t2 = 1 (SIGNED comparison -13<5)
versus unisgned
sltu $t2, $t0, $t1 # $t2 = 0 (huge number !<5 )

Question 33

Be ready to implement common C++ statements like for, while, do-while, if-else, switch in MIPS. You should be able to preserve C++ behavior of those statements completely.

Answer 33

PRACTICE

Question 35

Negative to binary

Answer 35

Ex: -53

52:
110100

Subtract from
1111 1111
00 11 0100

To get
1100 1011