OS Weekly Review 1

tags: Operating System

1. Definitions and Short Answers - week 1 (9/9 lectures)

   1. What is batch processing ? What are its advantages? Disadvantages?

      批次處理程式。 Advantage: 多使用者共用一台機器、可以指定執行時間。 Disadvantage: CPU 經常閒置(因I/O較慢)、一次一件工作、程式之間沒有交流。

   2. What is multiprogramming ? What disadvantage of batch processing does it address?

      一次處理多件工作。程式A 處理 I/O 時，用 CPU 去跑別的程式B，解決了batch processing 的 CPU 閒置問題。

   3. Compare multiprogramming and multitasking in terms of number of users, number of jobs running, and need for support features.

      	multiprogramming	multitasking
      number of users	multiple users	multiple users
      number of jobs	multiple jobs	multiple jobs
      support features	CPU scheduling I/O system memory management	file system virtual memory synchronization

   4. What is an instruction set architecture (ISA)? How is it different from a CPU or a processor?

      opcode, operand, register, addressing modes, assembly language, machine code,

      ISA: 用來控制 CPU 的基本指令。根據 CPU 的設計適用不同的ISA。

   5. What are reasons for the trend from single processor to multiprocessor architectures?

      增加 Thoughput
      Energy efficiency: same performance but much lower power!

   6. What makes tightly coupled multiprocessors difficult to scale to a large number of processors?

      因為太多CPU在同一個裝置，會造成太大的耗能，就算採用NUMA形式能解決耗能過大的問題，但是NUMA的access memory time會變長，所以 difficult to scale to a large number of processors

   7. What are examples of real-time systems? How do they differ from high-performance systems?

      multimedia system, industrial control, flight or auto control, anti-lock brake

      不見得會很快，但是一定會在時限內完成工作

   8. What are examples of hard real-time vs soft real-time systems?

      soft real-time: multimedia streaming

      hard real-time: nuclear power plant controller

2. EdSim51 and 8051 - week 1 (9/11 lecture)

   1. What is an assembler?

      將 assembly code 組譯成 object code.

   2. Given the sample assembly program:

      ​​​​​​ORG 0000H
      ​​​​​​MOV 90H, #24H
      ​​​​​​END
      

      a. What is a directive in this assembly program, and how is it different from an instruction?

      ORG and END are directive, 跟 instruction 不同的是, directive並不會被組譯成 object program.

      b. What is an instruction ? What does the assembler do to an instruction?

      MOV 90H, #24H is an instruction, assembler 會將 instruction 組譯成 object code.

      c. What is an opcode in the above example? An operand ?

      MOV is an opcode in the above example.
      90H and #24H are operand.

   3. What does 90H refer to? What does #24H refer to? Why is there a # in front of 24H but not in front of 90H ?

      90H 代表 IDATA address 為 90(hex).
      #24H 代表 constant value 為 24(hex).
      #24H 前面有 # 的符號，代表的是純數值(constant value)。

   4. What is a NOP ? and how do you pronounce it?

      means "do nothing", pronounce "no operation".

   5. Why is 8051 called a Harvard architecture ? How is it different from a von Neumann architecture?

      Harvard architecture 是一種將 instruction 跟 data 分開儲存的計算機結構，因此 8051 是一種 Harvard architecture。
      von Neumann architecture 是一種將 instruction 跟 data 合併儲存的計算機結構。

   6. What is a PC in a processor? What are the ways PC value can change?

      PC(program counter) 指出 CPU 正在執行 program 的哪一個部分。
      PC 在 processor 抓取 instruction 後會增加，也可以使用 control transfer instruction 給予 PC 新的 value 。

   7. How many bytes is 8051’s code memory ? How many bits are needed to represent the code address?

      64KB.
      16bits.

   8. What is DPTR in 8051? How is it related to DPL and DPH ?

      DPTR(Data Pointer)，是 16 bits 的 register ，作為存取 data 的 pointer 使用。
      DPTR可一分為二，作為兩個 8 bits 的一般 register 使用，分別為 DPL 和 DPH。

   9. How big is the IDATA memory in 8051?

      256 Bytes

   10. What is a special-function register (SFR)?

       Can not be directly writable by normal instructions.

       Can be accessed by its name or by its address.

       Tied to some special function or status of the processor

   11. What is the meaning of simplex , half-duplex , and full-duplex communication? Which one is the UART (serial port)?

       simplex : A simplex communication channel only sends information in one direction.

       half-duplex : data can be transmitted in both directions on a signal carrier except not at the same time

       full-duplex : able to transmit data in both directions on a signal carrier at the same time

       full-duplex is UART(通用非同步收發傳輸器（Universal Asynchronous Receiver/Transmitter)

   12. if #24H refers to hex 24 integer value (“immediate”) in Intel assembly, why #FFH does not refer to hex FF integer value? Name two ways to express 0xFF in Intel assembly syntax.

       because first integer is F(since F is not in 0..9) therefore is not an immediate

       use #0FFH

   13. What is the meaning of MOV A, 17 in 8051 assembly, and how is it different from MOV A, #17 ? What about MOV A, 17H ? MOV A, #17H ?

       MOV A, 17: direct mode at decimal 17 (instead of hex)

       MOV A, #17: immediate mode which present in decimal

       MOV A, 17H: direct mode (IDATA address 0x17)

       MOV A, #17H: immediate mode which present in Hex

   14. What is a general-purpose input/output (GPIO) port? What are they called on 8051?

       通用型之輸入輸出的簡稱
       功能類似8051的P0—P3

   15. Why do you have to write a 0 bit to turn on an LED segment? Why write a 1 bit to turn off ?

       0的話會接地通電，製造大電位差，所以0是turn on

   16. What is an “immediate” operand?

       example: MOV A #17H
       上方的 #17H 就是 immediate operand.

   17. What is a "direct" operand?

       example: MOV A 17H
       代表 A = data in address 0x17 in IDATA
       上方的 17H 就是 "direct" operand

   18. How do you pronounce “UART”? What is another more descriptive term for UART?

       UART = Universal Asynchronous Receiver/Transmitter
       通用非同步收發傳輸器