Lecture 1: Machine Organization

Question 1

operating system

Answer 1

operating system

a program that acts as an intermediary between user of a computer and the computer hardware.

Question 2

computer system structure

Answer 2

1. hardware
2. operating system
3. application programs
4. users

Question 3

Machine Organization

Answer 3

1. CPU: a processor for interpreting and executing programs
2. Memory: for storing data and programs
3. Controller: mechanism for transferring data from/to outside world (devices). It transfers the data on the bus, through the bus
   Bus: sets of wires (zeros and ones), each “on” or “off”: move data and instructions within units of the machine. All data is interpreted as zeroes and ones (binary).

Question 4

Bus

Answer 4

The bus is divided into 2 sets:
data(what), address(where)

Primary movement of the bus:
Data is moved from:
1. From CPU to Memory
(and from Memory to CPU)
2. From CPU to the device controllers (disk)
3. From memory to device controllers (sometimes)

Question 5

CPU

Answer 5

Central Processing Unit
=ALU + Control Unit

CPU os responsible for fetching, decoding and executing instructions on the correct data.

Question 6

ALU

Answer 6

Arithmetic Logical Unit
= registers + function unit
-It stores and performs operations on data

Registers: storage units (for addresses, program counters, data)

Function Unit: arithmetic and logic Units

Question 7

Control Unit

Answer 7

• Interprets program instructions

- Makes sure the correct data is where it needs to be.

Question 8

Registers

Answer 8

• Fast Expensive Memory on the Processor
• 32-64 registers in ALU
• Each holds a “word”
• word is data size used in computation
• word is data transferrable over data bus at a time

Types: General Purpose Registers (GPR) and Status Registers

Question 9

Function Unit

Answer 9

• performs logical and arithmetic computations with data in registers
  e. g. ADD R1, R2 –> R1: =R1+R2
• Operations in FU may affect bits in status registers (e.g. overflow, zero flag)
• knows which operations to perform because it is controlled by signals from the Control Unit of the CPU

Question 10

General Purpose Register (GPR)

Answer 10

• All data used in computation is stored in General Purpose Registers.
• Set directly by software (assembly language instruction)

Question 11

Mem to CPU Operations (Assembly Language )

Answer 11

LOAD: Mem->Reg
STORE: Reg ->Mem

Question 12

Mem to Disk (System Calls)

Answer 12

• Request OS to perform service
• Causes it to cede control of CPU (trap)

READ R1: : Disk -> Reg

WRITE R1: : Reg -> Disk

Question 13

Status Register

Answer 13

• convey info about previous and current operation
  e. g. CPM R1, R2
• Set as “side effect” of software

Question 14

Program Counter (PC)

Answer 14

• register of the CPU that stores where the program where the program is stored in emory
• The register containing the address of the instruction in the program being executed.

Question 15

Instruction Register (IR)

Answer 15

register of a CPU’s control unit that holds the instruction currently being executed or decoded

Question 16

Control Circuitry (CC)

Answer 16

digital circuitry within the processor that coordinates data movements into, out of, and between a processor’s many sub-units.

Question 17

2 Roles of the OS

Answer 17

1. resource abstraction for applications: abstract from functionality of hardware (ease of use for programs, makes our programs, in a way, device independent)
2. resource sharing: protects, manages resources (CPU’s, memory, I/O devices)

Question 18

What is a resource?

Answer 18

Most are hardware: CPU, Memory, I/O devices

Question 19

Boostrap Loader

Answer 19

small program stored in ROM that runs part of OS

Question 20

BIOS

Answer 20

(no-volatile firmware on flash memory of motherboards) initialized hardware and runs the bootstrap loader - BIOS is part of hardware

Question 21

Control Unit Components

Answer 21

Fetch-Decode-Execute (FDE) Unit + PC + IR