Introduction OS

Question 1

Multiprocessors systems dominates
the computing market

Answer 1

Advantages of it include:

a. Increased throughput

b. Economy of scale

c. Increased reliability – graceful degradation
or fault-tolerant.

Question 2

There are two kinds of multiprocessing

Answer 2

Asymmetric Multiprocessing and Symmetric multiprocessing

Question 3

Asymmetric Multiprocessing

Answer 3

– Each processor is assigned a specific task:

   \+  A boss processor controls the system.
   \+ The other processors look to the boss 
    for instruction.

Question 4

Symmetric multiprocessing

Answer 4

– Each processor performs all tasks

Question 5

Multicore

Answer 5

The CPU that design is to include multiple
computing cores on a single chip. Or to put it simply: Multicore mean 2 or more than 2 CPU equipped in one chip.

Question 6

Singlecore

Answer 6

Which mean only 1 CPU equipped in one chip.

Question 7

Muliticore can be more efficient than multiple
chips with single cores

Answer 7

Because ON-CHIP communication is faster
than BETWEEN-CHIP communication

Question 8

Interrupts

Answer 8

are signals sent to the CPU by external devices, normally I/O devices. They tell the CPU to stop its current activities and execute the appropriate part of the operating system

Question 9

There are three types of interrupts

Answer 9

1. Hardware Interrupts
2. Software Interrupts
3. Traps

Question 10

Hardware Interrupts

Answer 10

are GENERATED by hardware devices to SIGNAL that they need some attention from the OS

Question 11

Hardware Interrupts

Answer 11

are generated by hardware devices to signal that they need some attention from the OS

Question 12

Software Interrupts

Answer 12

are generated by programs when they want to request a system call to be performed by the operating system

Question 13

Traps

Answer 13

are generated by the CPU itself to INDICATE that some error or condition occurred for which assistance from the OS is needed

Question 14

There are two CPU Execution Mode

Answer 14

1. User mode
2. Kernel or supervisor mode

Question 15

User mode

Answer 15

is restricted in that certain instructions cannot be executed, certain registers cannot be accessed, and I/O devices can not be accessed

• Can only execute a subset of instructions
• Can only reference a subset of memory locations

Question 16

Kernel or supervisor mode

Answer 16

Kernel mode has NONE of the restrictions
- A system call will set the CPU to kernel mode, as will traps and interrupts
- Can execute all machine instructions
- Can reference (?) all memory locations

Question 17

Context switch

Answer 17

switching from running a user level process to the OS kernel and to other user processes before the current process is resumed

Question 18

The CPU performs the following actions in response to an interrupt

Answer 18

1. Using the pointer to the current process control block
   
   • The state and all register values for the process
     are saved for use when the process is later
     restarted
2. The CPU mode bit is switched to supervisory mode
3. Using the pointer to the interrupt handler table and the interrupt vector
   -The location of the kernel code to execute is
   determined
   
   • The interrupt vector is the interrupt request
     (IRQ) for hardware interrupts and an argument to
     the interrupt assembly language instruction for
     software interrupts
4. Processing is switched to the appropriate portion of the kernel

Question 19

There are 4 broad tasks performed by an operating system

Answer 19

Process Management
Memory Management
File System Management
Device Management

Question 20

Process Management

Answer 20

 A process is an executing program
 It consists of code, data, a certain set of resources allocated to it, and one or more threads of
execution through the code
 The OS manages the allocation of resources to these processes, and also provides system calls to
manage these processes

Question 21

Memory Management

Answer 21

 Memory must be shared between the OS and an application program
 The OS must manage the allocation of memory to processes and control the memory management
hardware that determines which memory locations a process may access

Question 22

File System Management

Answer 22

 Computers process information that must be transmitted, processed, and stored
 File systems are an abstract organized collection of file system objects
 The OS provides primitives to manipulate these objects process may access

Question 23

Device Management

Answer 23

 Information is sent through a computer’s input and output devices
 Processes access these devices using the system call interface
 The OS tries to manage devices in a manner that makes them efficiently shared among all processes
requiring them
 A system call is a programming interface to the services provided by the OS, typically written in C/C++

Question 24

Design Goals

Answer 24

 At the highest level, system design is dominated by the choice of hardware and system type
 Beyond this level, the requirements can be divided into two groups:
 User goals: include convenience, reliability, security, and speed
 System goals: include ease of design, implementation, maintenance, flexibility, and efficiency

Question 25

Implementation

Answer 25

o Operating systems were firstly written in assembly, but nowadays C/C++ is the language
commonly used

o Small blocks of assembly code are still needed, especially related to

 * Low level I/O functions in device drivers
 * Turning interrupts on and off
 * The Test and Set Instruction for Synchronization 
  Facilities

o Using higher level languages allows the code to be written faster
* It also makes the OS much easier to port to
different hardware platforms

Question 25

Implementation

Answer 25

o Operating systems were firstly written in assembly, but nowadays C/C++ is the language
commonly used

o Small blocks of assembly code are still needed, especially related to

 * Low level I/O functions in device drivers
 * Turning interrupts on and off
 * The Test and Set Instruction for Synchronization 
  Facilities

o Using higher level languages allows the code to be written faster
* It also makes the OS much easier to port to
different hardware platforms