The Workflow for FEED Phase

Introduction

This workflow is a good practice guidance to Engineering Managers and supporting personnel for the delivery of technical integrity. It is an ‘aide-memoir’ that highlights the key deliverables and activities throughout the lifecycle of a typical FEED project.

FEED is broken into six phases:

Phase 1: Scope Definition and Engineering Execution Strategy

Phase 2: Commencement of FEED Design

Phase 3: Initial FEED Development and Hazard Identification

Phase 4: Initial Design Review & Audit

Phase 5: FEED Design Approval (AFD)

Phase 6: Final Reviews and Feed Report Compilation

The workflow shown in the follow Road Map illustrates the execution sequence on a generic FEED Project. The vertical columns show activities that can be undertaken concurrently whilst the sequential flow of work is across the Road Map. As the deliverables and activities in each phase are completed, work can transition into the next phase.

Situations will arise when work will need to be be done out of sequence, typically to meet a demanding project schedule. Use of the workflow allows the risks of out-of-sequence working to be identified and the necessary mitigation strategies to be put in place.

HBP’s corporate governance and assurance of Engineering will measure compliance with the workflow and ensure out-of-phase working is being identified and managed. This document contains a copy of the FEED Road Map and includes detailed descriptions of the activities, the key engineering disciplines and supporting documentation.
Phase 1: Scope Definition and Engineering Execution Strategy

Preparation for commencement of detail design. To evaluate FEED deliverables to ensure engineering is sufficiently mature for detail design to progress in a controlled and minimal change environment. To confirm Engineering Execution Plan.

	Activities / Deliverables	Description	Supporting Documentation
1	Engineering Execution Plan & Engineering Organisation Chart	Create Engineering Execution Plan complete with key supporting documents / information.
2	Preparation/Validation of Conceptual Study Report/BoD	Confirm maturity of Conceptual Design report. Identify any areas of concern and ensure these are captured on the Technical Risk Register.
3	Project Baseline Standards	Establish which codes, standards and specifications are to be utilised, e.g.. Corporate, project, client, and confirm procedure. Include in Engineering Execution Plan and/or Discipline Job Design Specifications.	Engineering Baseline Standards, Document No. (DOCUMENT CODE)
4	Engineering Audit Schedule	Create formal schedule to identify when technical integrity audits, design reviews, HAZIDS, HAZOPS, etc are to be carried out. Align to Level 3 Engineering Plan and include in Engineering Execution Plan.	Technical Safety Events Schedule (Lead Technical Safety Engineer)
5	Technical Risk Register	Create formal Technical Risk Register identifying all possible risks associated with the engineering design.
6	Integrated Engineering Systems	Agree engineering design tools to be used and confirm that system hardware, software and support is available. Include issues such as PDMS or PDS, Cats and Specs, survey methods, dimensional control techniques, etc. Document and record in the Engineering Execution Plan and discipline job design specifications.	Engineering Systems Project Start-up Manual, Document No. (DOCUMENT CODE)
7	QRA & FRA Strategy	Establish status of project Quantitative Risk Assessment (QRA), Fire Risk Assessment (FRA) and Emergency Escape & Rescue Assessment (EERA) information and confirm methodology for timely delivery into engineering design process. Agree accountability for delivery, e.g.. Client, 3rd party, HBP, and record in Engineering Execution Plan.	Hazard Management Philosophy, (DOCUMENT CODE): Hazard & Risk Management, (DOCUMENT CODE)
8	Discipline Job Design Specification	Define the key project specific design parameters and operational constraints that are applicable to the appropriate discipline for the detailed design of the project. To identify key individuals , roles and responsibilities, design tools, key codes and standards, etc.
9	Level 3 Engineering Plan	Agree work breakdown structure, develop CTRs and create level 3 integrated engineering plan covering all disciplines. To be included in Engineering Execution Plan.
10	Confirm CE Compliance Strategy	Review and confirm strategy for CE Compliance. Ensure discipline Lead Engineers are aware of their responsibilities and appropriate resources / measures are in place.	Corporate CE Compliance Strategy (DOCUMENT CODE); Project Compliance with Pressure Equipment Regulations (DOCUMENT CODE); Pressure Equipment Regulations Guidelines (DOCUMENT CODE); ATEX Guidelines, (DOCUMENT CODE); Machinery Directive Guidelines, (DOCUMENT CODE); Electromatic Compatibility Regulations Guidelines, (DOCUMENT CODE); MC, The Electrical Equipment (Safety) Regulations Guidelines, (DOCUMENT CODE).
11	Prepare Interface Register	Develop interface register to ensure all interfaces are identified and managed.	The Electrical Equipment (Safety) Regulations Guidelines No: (DOCUMENT CODE)

Phase 2: Commencement of FEED Design

To formally kick off the Engineering Design Process in accordance with the project execution plan and to ensure that key engineering strategies / philosophies are in place.

	Activities / Deliverables	Description	Supporting Documentation
1	Safety Critical Systems/Elements and Performance Standards	Confirm safety critical systems / elements and set appropriate performance standards. i.e. functionality, reliability and survivability.	Hazard Management Philosophy, (DOCUMENT CODE); Hazard & Risk Management, (DOCUMENT CODE); Design Verification Activities (under DCR), (DOCUMENT CODE); Platform Safety Case.
2	Document Distribution Matrix	Create formal document distribution matrix to ensure all disciplines & departments receive all necessary design information in a timely manner.
3	Structural Integrity Interface	Ensure structural integrity interfaces are identified & visible to Project, e.g. HBP / Client focal points, Technical Authorities, Independent Verification Bodies, etc.
4	Material Selection Report	Report defining the requirements and specifications of necessary material.	HBP Corporate Material Engineering Specifications.
5	Hazard Management Plan	Create Hazard Management Plan identifying all key hazards, technical safety activities and the approach to managing Major Accident Hazards (MAH) in the design.	Hazard & Risk Management, (DOCUMENT CODE); Management of Functional Safety Guideline (DOCUMENT CODE)
6	Piping Specifications	Develop / confirm baseline piping specifications, utilising HBP Corporate specifications where possible.	HBP Corporate Piping Specifications.
7	PDMS Catalogues	Ensure PDMS catalogues are populated & available for all affected disciplines, utilising HBP Corporate data, i.e. CPC, where possible.
8	CMSS Philosophy	The purpose of this task is to define and prepare the assurance activities to be undertaken aligned with the project categorisation.	Develop Control Monitoring and Safety Systems (CMSS) Philosophy covering key instrumentation and control systems e.g. Process Control System (PCS), Emergency Shutdown System (ESD) and Fire and Gas (F&G).

Phase 3: Initial Design Development and Hazard Identification

To develop initial design deliverables to Inter Discipline Review (IDC) stage and identify key hazards.

	Activities / Deliverables	Description	Key Discipline	Supporting Documentation
1	HAZID	Perform hazard identification studies, as identified on Engineering Audit Schedule / Technical Safety Events Schedule.	Technical Safety	Project Hazard Identification (HAZID) (DOCUMENT CODE); Engineering & Design Reviews, (DOCUMENT CODE).
2	ENVID	Formal assessment of environmental aspects associated with a modification or a change, and to propose prevention or mitigating measures.	Technical Safety	Environmental Impact Identification (ENVID) (DOCUMENT CODE); Engineering & Design Reviews, (DOCUMENT CODE).
3	PFD IDC	Issue Process Flow Diagrams (PFD’s) on formal Inter-Discipline Review (IDC).	Process
4	Shutdown & Blowdown Philosophy	Explains the measures to shutdown safely and control blowdown and how this will be achieved.	Process
5	P&ID’s IDC	Issue Piping & Instrumentation Diagrams (P&ID’s) on formal Inter-Discipline Review (IDC).	Process
6	Plot Plans / Layouts IDC	Issue equipment Plot Plans / Layouts on formal inter-Discipline Review (IDC).	Piping and Layouts
7	HIPPS Review	Initial review to establish requirements for a High Integrity Pressure Protection System.	Instruments	Management of Functional Safety, (DOCUMENT CODE)
8	Dropped Object Study	Identify and assess the potential risks to drilling, production, process equipment, and manned areas from dropped or swinging objects. Where the consequence of a dropped object is considered significant, to propose prevention or mitigating measures.	Technical Safety
9	Mechanical Handling Strategy	Develop Mechanical Handling Strategy including general approach / constraints, platform crane limits, installation philosophy, operation and maintenance, etc.	Mechanical and Structural
10	Particular Materia Appraisals (PMA)	Where required, i.e. where Corporate PMA’s or EAM’s are not suitable, develop new PMA’s and obtain approval from Notified Bodies (NoBo’s.	PED Focal Point
11	C&E IDC	Issue Cause & Effects for formal Inter-Discipline Review (IDC).	Process and Instruments
12	Hazardous Area Layouts IDC	Issue Hazardous Area Layouts for formal Inter-Discipline Review (IDC).	Technical Safety
13	Fire Risk Assessment (FRA)	Determines Fire & Explosion scenarios and identifies requirements for prevention, control and mitigation measures.	Technical Safety
14	Blast Design Philosophy	Develop philosophy that assesses potential explosion hazards and identifies appropriate blast loadings to be applied to the engineering design process, e.g.. Vessels, pipe supports, structural steel, etc.	Technical Safety
15	TR Impairment Study	Assessment of the vulnerability of a Temporary Refuge and demonstration of its capability to sustain life for a specified duration when under attack by fire, explosion and toxic gases.	Technical Safety	Fire Hazards Assessment, Blast Assessment, Dispersion Assessment, Emergency, Escape and Rescue Assessment, Heat Stess Assessment
16	Equipment List & Data Sheets	Create master project equipment list identifying all major items of tagged equipment, e.g. vessels, pumps, motors, generators, hydrocycolnes, chemical injection packages, electrical switchgear, control panels, etc.	Mechanical
17	Emergency Escape & Rescue Assessment (EERA)	To identify requirements for emergency escape & rescue, e.g. lifeboats, escape routes, plant layout, etc.	Technical Safety
18	PFP / AFP Philosophy	Develop philosophy that identifies requirements for Passive Fire Protection (PFP) and/or Active Fire Protection (AFP).	Technical Safety
19	Power System Analysis	Check power system capacities for increase power requirements for new equipment (Brownfield).	Electrical
20	Preliminary Weight Report	Prepare preliminary Weight report.	Structural

Phase 4: Initial Design Review and Audit

To confirm that the initial design development is robust.

	Activities / Deliverables	Description	Key Discipline	Supporting Documentation
1	Hazardous Area Review	Formal Engineering discipline review of hazardous area layouts to confirm requirements for the correct selection and location of equipment.	Technical Safety	Hazard and Risk Management Procedure (DOCUMENT CODE); Engineering & Design reviews, (DOCUMENT CODE)
2	P&ID Review	Formal Engineering discipline review of P&ID’s to confirm design basis.	Process, Piping, Technical Safety, Instruments
3	Plot Plans / Layout / 3-D Model Review	Formal Engineering review of Plot Plans / Layouts. The review shall ensure that the layout design complies with the required technical, safety, operability and maintainability standards. Makes sure the layout is cost effective, ensures the constructability of the work and agrees the layout basis on which the detailed design can proceed.	Piping and Layouts, Structural, Mechanical, Electrical, Technical Safety, Process	Engineering & Design Reviews, (DOCUMENT CODE)
4	C&E Review	Formal review of Cause & Effects diagrams to confirm design basis and alignment with Hazard Management Plan.	Instruments, Process, Technical Safety	Hazard and Risk Management Procedure (DOCUMENT CODE); Engineering & Design reviews, (DOCUMENT CODE); Management of Functional Safety Guideline (DOCUMENT CODE)
5	Technical Audit	Obtain confirmation, by sampling of project documentation, that the engineering of the project is to the required standard and free from errors.	Independent (Corporate Engineering)	Technical Audit Procedure (DOCUMENT CODE)

Phase 5: FEED Design Approval (AFD)

To ‘Freeze’ the Process design, and develop dependent design & procurement activities.

	Activities / Deliverables	Description	Key Discipline	Supporting Documentation
1	Final Design review	Demonstartion that all of the design and review activities relevant to achieving design integrity have been performed.	Technical Safety	Final Design Review – (DOCUMENT CODE)
2	PUWER Assessments	Conduct initial PUWER assessment typically by review of PDMS model and/or vendor / equipment supplier information received to date.	Technical Safety, Mechanical	Engineering & Design Reviews, (DOCUMENT CODE)
3	HAZOP	Hazard and Operability Studies, a systematic multi-discipline study based on the applications of guidewords to identify causes of potential hazards and operability constraints in a facility.	Process, Technical Safety	Dependent on Project updated P&ID’s and C&E’s may be prepared from commented IDC’s from Phase 3 Formal HAZOP, (DOCUMENT CODE); Engineering & Design Reviews, (DOCUMENT CODE) – Note: additional HAZOP’s may be required, i.e. earlier or later in the project. PEM to consult with Process & Technical Safety Lead Engineers.
4	BAT Report	The Final report which analyses the major environmental issues that have been considered as part of the process to select the final option from the various alternatives considered. Thus preventing, or eliminating, or where the alternatives are not practicable, to then limit or reduce environmental impacts associated with the selected option.	Technical Safety	Procedure for Selection of Best Available Techniques (BAT) Procedure No: (DOCUMENT CODE)
5	Constructability Review	Conduct formal Constructability Reviews to ensure safe and efficient installation of plant & equipment.	Affected disciplines + Construction / Implementation Group	Engineering & Design Reviews, (DOCUMENT CODE)
6	P&ID AFD	Issue Approved For Design (AFD) Process and Instrumentation Diagrams.	Process
7	C&E AFD	Issue Approved For Design (AFD) Cause & Effects.	Instruments
8	Process Data Sheets AFD	Issue Approved For Design (AFD) Process Data Sheets.	Process
9	HP / LP Interface Listing	Identify all HP / LP interfaces on formal register and ensure that all have been addressed satisfactorily via HAZOP’s and / or individual reviews.	Process
10	Holds Register	Develop register to record & manage post AFD design holds.	Engineering Manager
11	SIL Assessments	Conduct assessment to determine target Safety Integrity Level (SIL). Note: Where the target SIL is 3, then it is likely that a High Integrity Pressure Protection System (HIPPS) will be required. If the value is found to be 1 or 2, then a HIPPS will not be required.	Instruments	Management of Functional Safety, (DOCUMENT CODE)
12	HIPPS Study	Conduct study to formally identify the performance requirements of the High Integrity Pressure Protection System (HIPPS) and demonstrate that it is robust. Should include dynamic study for a range of transient conditions.	Process	Management of Functional Safety, (DOCUMENT CODE)
13	Qualitative Risk Assessment (QRA)	Multi-disciplinary study of hazards, the likeihood of their occurrence and potential consequences in terms of harm to people and the environment.	Technical Safety	Fire Hazards Assessment, Blast Assessment, Dispersion Assessment, Emergency, Escape and Rescue Assessment, Heat Stess Assessment
14	HIPPS Reliability Study	Conduct study to formally demonstrate that the High Integrity Pressure Protection System (HIPPS) complies with the reliability & availability criteria for the Project, e.g. as stipulated in the performance standards.	Instruments	Management of Functional Safety, (DOCUMENT CODE)
15	Flow Assurance	Conduct flow assurance studies to demonstrate the process design under a range of flow conditions, i.e. start-up to 100%.	Process
16	EDAS Stage Gate Reviews	Demonstrate adherence to the EDAS Task Performance Crite-ria appropriate for Project Category.	Engineering Management
17	Technical Peer Review	Demonstrate adherence to the EDAS Task Performance Criteria appropriate for the Project Category and to ensure that engineering personnel are aware of EDAS requirements and adequately explain how those requirements are being fulfilled.	Engineering Management

Phase 6: Final Reviews and FEED Report Compilation

To ensure all final design deliverables are completed and that client and statutory obligations are satisfactorily resolved.

	Activities / Deliverables	Description	Key Discipline	Supporting Documentation
1	FEED Report	Collate all discipline inputs and finalise study report.	Project Management	All Discipline Reports and discipline drawings etc.

在系统托盘中显示

‘建立项目(Project)，创制如图级联菜单，分别命名为mnuMain、mnuWork、mnuExit。

Option Explicit
Private Type NOTIFYICONDATA
cbSize As Long
hWnd As Long
uID As Long
uFlags As Long
uCallbackMessage As Long
hIcon As Long
szTip As String * 64
End Type
Dim tnid As NOTIFYICONDATA
Private Const NIM_ADD = &H0
Private Const NIM_MODIFY = &H1
Private Const NIM_DELETE = &H2
Private Const NIM_MOUSEMOVE = &H200
Private Const NIF_MESSAGE = &H1
Private Const NIF_ICON = &H2
Private Const NIF_TIP = &H4
Private Const DOUBLE_CLICK_LEFT = &H203
Private Const BUTTON_LEFT_DOWN = &H201
Private Const BUTTON_LEFT_UP = &H202
Private Const DOUBLE_CLICK_RIGHT = &H206
Private Const BUTTON_RIGHT_DOWN = &H204
Private Const BUTTON_RIGHT_UP = &H205
Private Declare Function Shell_NotifyIcon Lib “shell32” Alias “Shell_NotifyIconA” (ByVal dwMessage As Long, pnid As NOTIFYICONDATA) As Boolean

Private Sub Form_Load()
tnid.cbSize = Len(tnid)
tnid.hWnd = Me.hWnd
tnid.uID = 1&
tnid.uFlags = NIF_ICON Or NIF_TIP Or NIF_MESSAGE
tnid.uCallbackMessage = NIM_MOUSEMOVE
tnid.hIcon = Me.Icon
tnid.szTip = “系统托盘样例” & Chr$(0)
Shell_NotifyIcon NIM_ADD, tnid
Me.Hide
App.TaskVisible = False
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
‘为相应事件添加对应代码
Dim MSG As Long
MSG = X / Screen.TwipsPerPixelX ‘512
Select Case MSG
Case DOUBLE_CLICK_LEFT ‘515

Case BUTTON_LEFT_DOWN ‘513
OpenForm Me
Case BUTTON_LEFT_UP ‘514

Case DOUBLE_CLICK_RIGHT ‘518

Case BUTTON_RIGHT_DOWN ‘516

Case BUTTON_RIGHT_UP ‘517
PopupMenu mnuMain, , , , mnuWork
End Select
End Sub

Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
EndApp
End Sub

Private Sub Form_Resize()
If Me.WindowState = 1 Then
Me.Hide
App.TaskVisible = False
End If
End Sub

Private Sub mnuExit_Click()
EndApp
End Sub

Private Sub EndApp()
Unload Me
tnid.cbSize = Len(tnid)
tnid.hWnd = Me.hWnd
tnid.uID = 1&
Shell_NotifyIcon NIM_DELETE, tnid
End
End Sub

Private Sub OpenForm(ByVal frmShow As Form)
frmShow.Show
App.TaskVisible = True
End Sub

二十四史简介——隋书

《隋书》共八十五卷，其中帝纪五卷，列传五十卷，志三十卷。本书由多人共同编撰，分为两阶段成书，从草创到全部修完共历时三十五年。
唐武德四年（公元621年），令狐德提出修梁、陈、北齐、北周、隋等五朝史的建议。次年，唐朝廷命史臣编修，但数年过后，仍未成书。贞观三年（公元629年），重修五朝史，由魏征“总知其务”，并主编《隋书》。
《隋书》的作者都是饱学之士，具有很高的修史水平。
《隋书》是现存最早的隋史专著，也是《二十五史》中修史水平较高的史籍之一。
首先，它有明确的指导思想。下令修隋史的唐太宗亲历了灭隋的战争，在执政之后，他经常谈论隋朝灭亡的教训，明确提出“以古为镜，可以见兴替“的看法。
汲取历史教训，以史为鉴就成了修隋史的指导思想。其次，《隋书》弘扬秉笔直书的优良史学传统，品评人物较少阿附隐讳。主编魏征刚正不阿，他主持编写的纪传，较少曲笔，不为尊者讳。如隋文帝之“刻薄”专断，“不悦诗书”，“暗于大道”，隋炀帝矫情饰貌，杀父淫母，“锄诛骨肉，屠剿忠良”等情况，都照实写来，了无隐讳。
再次，《隋书》保存了大量政治、经济以及科技文化资料。其中十志记载梁、陈、北齐、北周和隋五朝的典章制度，有些部分甚至追溯到汉魏。

AutoCAD 的文件 DXF 组码

DXF的基本惯例

DXF格式是特定版本AutoCAD图形文件中所包含的全部信息的标记数据的一种表示方法。

标记数据的意思是指在每个数据元素前都带一个称为组码的整数。组码的值表明了其后数据元素的类型，也指出了数据元素对于给定对象（或记录）类型的含意。实际上，图形文件中所有用户指定的信息都能够以DXF文件格式表示。在AutoLISP和ARX应用程序中使用的DXF格式与上述格式基本相同，只是在某些数据组上存在着细微的差别。

如不作特殊说明，本节中所出现的组码都可以应用于DXF文件、AutoLISP应用程序和ARX应用程序。当组码说明对于应用程序和DXF文件有所不同时（或只适用于其中之一），在组码的说明前有如下提示符：

APP只用于应用程序的说明

DXF只用于DXF文件的说明

如果组码说明对DXF文件和应用程序都适用，那么没有提示符；否则将显示适当的提示符。

组码范围

组码将与组码关联的值（组值）定义为整型、浮点数型或字符串型。具体说明如下表：

组码范围组码范围组值类型

0-9 字符串（最多255个字符，对于UNICODE字符串则更少）

10-59 双精度三维点

60-79 16位整数值

90-99 32位整数值

100 字符串（最多255个字符，对于UNICODE字符串则更少）

102 字符串（最多255个字符，对于UNICODE字符串则更少）

105 表示十六进制句柄值的字符串

140-147 双精度标量浮点值

170-175 16位整数值

280-289 8位整数值

300-309 任意文字字符串

310-319 表示二进制数据组的十六进制值的字符串

320-329 表示十六进制句柄值的字符串

330-369 表示十六进制对象标识符的字符串

999 注释（字符串）

1000-1009 字符串（最多255个字符；对于UNICODE字符串则更少）

1010-1059 浮点值

1060-1070 16位整数值

1071 32位整数值

按数字次序排列的组码

下表给出了组码（或组码范围）及其说明。在表中，“固定”表示该组码的用途固定不变，非固定组码的用途将随上下文变化。

按数字次序排列的图元组码

组码说明

-5APP：persistentreactor链表

-4APP：条件运算符（仅用于ssget）

-3APP：扩展数据(XDATA)标记（固定）

-2APP：图元名引用（固定）

-1APP：图元名。每次打开图形时它都改变，且不被保存。（固定）

0 表示图元类型的文字字符串（固定）

1 图元的主要文字值

2 名称（属性标记、块名称等）

3-4 其他的文字值或名称值

5 图元句柄。最多16位十六进制数字的文字字符串（固定）

6 线型名（固定）

7 文字样式名（固定）

8 图层名（固定）

9 DXF：变量名标识符（仅用于DXF文件的HEADER区域）。

10 主要点。此点为直线或文字图元的起点，圆的圆心等等。

DXF：主要点的X值（其后为Y和Z值的组码20和30）

APP：三维点（三个实数构成的表）

11-18 其他点。

DXF：其他点的X值（其后为Y和Z值的组码21-28和31-38）

APP：三维点（三个实数构成的表）

20,30 DXF：主要点的Y和Z值

21-28,

31-37 DXF：其他点的Y和Z值

38 DXF：如果非零，则为图元的标高。只在R11以前的AutoCAD输出的DXF文件中存在

39 如果非零，则为图元的厚度（固定）

40-48 浮点值（文字高度、比例因子等）

48 线型比例。浮点标量值。缺省值适用于所有图元类型。

49 可重复的浮点值。一个图元中的可变长度表（例如LTYPE表中的虚线长度）中可出现多个组码49。组码7x总是在第一个组码49前出现，用于指定表的长度。

50-58 角度（在DXF文件中单位为度，在AutoLISP和ARX应用程序中单位为弧度）。

60 表示图元可见性的整数值。不赋值或值为0时表示可见；为1时表示不可见。

62 颜色代码（固定）

66 “图元跟随”标志（固定）

67 空间，即模型空间或图纸空间（固定）

68 APP：表示视口打开但不可见、未激活或者关闭。

69 APP：视口标识数字。

70-78 整数值，如重复部分的计数器、标志位或模式等。

90-99 32位整数值

100 子类数据标记（把继承下来的类名当作字符串）。由具体类继承下来的所有对象和图元类都必须有此项。此标记用于分离某个对象中由不同的类定义的数据。它也满足从ARX继承下来的每个独立的具体类的DXF命名需要（请参见子类标记!AL(`XREF_11832_al_u05_c’,1)）。

102 控制字符串，其后为“{<任意名称>”或”}”。除了字符串必须以”{“开始外，它与外部数据组码1002类似。其后可跟任意字符串，且此字符串的解释取决于应用程序。另一个可用的控制字符串为”}”，它标识组的结束。如上所述，除了在执行图形核查操作期间外AutoCAD一般不解释这些字符串；它们仅用于应用程序。

105 DIMVAR符号表条目对象句柄。

210 拉伸方向（固定）。

DXF：拉伸方向的X值

APP：三维拉伸方向矢量

220,230 DXF：拉伸方向的Y和Z值

280-289 8位整数值

300-309 任意的文字字符串

310-319 任意二进制数据组，与组码1004具有相同表示法和限制：最长为254个字符的十六进制字符串表示最长为127个字节的数据数据组。

320-329 任意对象句柄。句柄值保留原样，在执行INSERT和XREF操作时它们不被转化。

330-339 软键指针句柄。任意指向同一DXF文件或图形中的其他对象的软键指针，在执行INSERT和XREF操作时被转化。

340-349 硬键指针句柄。任意指向同一DXF文件或图形中的其他对象的硬键指针，在执行INSERT和XREF操作时被转化。

350-359 软键从属句柄。链接到同一DXF文件或图形中其他对象的任意软键从属链接，在执行INSERT和XREF操作时被转化。

360-369 硬键从属句柄。链接到同一DXF文件或图形中其他对象的任意硬键从属链接，在执行INSERT和XREF操作时被转化。

999 DXF：999组码表示其后为注释字符串行。DXFOUT不在DXF输出文件中包括此组；DXFIN能识别词组码，但忽略其后的注释。通过999组码，用户可以在所编辑的DXF文件中包括注释。

1000 扩展数据中的ASCII字符串（最长255个字节）。

1001 扩展数据的已注册应用程序名（ASCII字符串，最长31个字节）。

1002 扩展数据控制字符串（”{“或”}”）。

1003 扩展数据图层名。

1004 扩展数据中的字节数据组（最长127字节）。

1005 扩展数据中的图元句柄。文字字符串，最多16位十六进制数字。

1010 扩展数据中的点

DXF：X值（其后跟组码1020和1030）

APP：三维点

1020,1030 DXF：点的Y和Z值

1011 扩展数据中的三维世界空间位置：X值（其后跟组码1021和1031）：三维点

1021,1031 DXF：世界空间位置的Y和Z值。

1012 扩展数据中的三维世界空间位移：X值（其后跟组码1022和1032）：三维矢量

1022,1032 DXF：世界空间位移的Y和Z值

1013 扩展数据中的三维世界空间方向

DXF：X值（其后跟组码1022和1032）

APP：三维矢量

1023,1033 DXF：世界空间方向的Y和Z值

1040 扩展数据浮点值。

1041 扩展数据距离值。

1042 扩展数据比例因子。

1070 扩展数据16位符号整数。

1071 扩展数据32位符号整数。

对象和图元的组码

在DXF格式中，对象的定义与图元的定义不同：图元有图形表示，而对象则没有图形表示。例如，词典是对象而不是图元。对象通常作为非图形对象来使用，图元则作为图形对象来使用。

在DXF文件中，图元可以出现在BLOCK和ENTITIESE区域中。两个区域中图元的用法一样。某些定义图元的组码始终会出现，而其他的组码仅在它们的值与缺省值不同时才出现。

读取DXF文件的程序不应该假定说明图元的组码是按照给定次序出现的。与说明图元的组码相连的0组码表示此图元已结束。0组码将开始新图元或表示此区域已结束。注意如果用户以表驱动方式（即忽略未定义的组码，且对图元中的组码次序不做任何假定）编写DXF处理程序，那么该程序将比较容易针对AutoCAD的后续版本做调整。因为AutoCAD的性能将不断得到增强，所以图元中将添加一些新的组码以提供更多的功能。

二十四史简介——北史

《北史》一百卷，其中本纪十二卷，列传八十八卷。记述北朝从公元386年到618年，魏、齐（包括东魏）、周（包括西魏）、隋四个封建政权共二百三十三年的历史。作者李延寿，唐初相州（今河南安阳）人，曾任史官，参与修撰《隋书》、《晋书》，并另外著有《南史》。
《北史》主要在魏、齐、周、隋四书基础上删订改编而成，但也参考了当时所见各种杂史，增补了不少材料。
总的来看，《北史》虽有内容偶呈芜杂之弊，但毕竟体例完整、材料充实、文字简炼，在后代颇受重视，以致魏、齐、周三书唐以后皆残缺不完，后人又多取《北史》加以补足。作为研究北朝历史的资料，《北史》与魏、齐、周、隋四书有互相补充的作用，不可偏废。