برمجة النظم

رابعة حاسب محاضرة (١)

دآتور/ أحمد الحربي

- This course has two major objectives: to teach procedures for the

design of software systems and to provide a basis for judgment in

the design of software.

- Machine structure and the basic tasks of an operating system can be

given by the following diagram:

People Application programming

Macro ProcessorsAssemblersCompilers Loaders Text editors Debugging aids Searching and sorting

I/O programs

File systems

Scheduler Libraries Memory management

Device management

Figure 1.1 Foundations of system programming

Machine Structure

Figure 1.2 shows the general hardware organization of a computer

system.

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- Memory is the device where information is stored.

- Processors are the devices that operate on this information.

يسمى 0 أو 1وآل من )ones & zeros( تحفظ في شكل informationوآما تعرفون أن

binary digit ويحفظ في وحدة تسمى bit وهذه bits تجمع في unitsتسمى :

Words, characters, or bytes.

,byte( يحدد للـ address وآل addressـ تحدد بMemory Locationsحيث أن

word, character.(

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- The contents of a word may be interpreted as data (values to be

operated on) or instructions (operations to be performed).

- A processor is a device that performs a sequence of operations

specified by instructions memory.

- Information in memory is coded into groups of bits that may be

interpreted as characters, instructions, or numbers.

- A code is a set of rules for interpreting groups of bits, e.g., codes

for representation of decimal digits (BCD), for characters

(EBCDIC, or ASCII), or for instructions (specific processor

operation codes).

- The I/O processors are concerned with the transfer of data between

memory and peripheral such as disks, drams, CD-ROMs, printers,

and typewriters.

- The CPUs are concerned with manipulations of data stored in

memory.

: سوف نقوم بدراسة آل منcourseخالل هذا

Assemblers, Macros, Loaders, and Compilers

. لهمapplicationsبالتفصيل وآذلك عمل

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.programming system األساسية للـ componentsآل ذلك هو عبارة عن

• Assemblers:

They are programs aim to translate assembly language into machine

language.

Machine Language Translation or (Object Program)

Assembler

Assembly Program Or (Source Program)

• Loaders:

فان هذا البرنامج يوضع في الذاآرة وينفذ object program ينتج assemblerبمجرد أن

أيضًا المبرمج يجب أن يحول برنامجه آما سبق مع آل . في الذاآرةassemblerمع ترك

.قتًا طويًالمرة تنفيذ، وهذا يأخذ و

آخرى تسمى componentولحل مشكلة إطالة الوقت، فان مبرمجي النظم طورو

Loader.

- A loader is a program that places programs into memory and

prepares them for execution.

: هماSubroutinesيوجد نوعين من

Closed and open Subroutines.

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- An open subroutine or “macro definition” is one whose code is

inserted into the main program (flow continuous).

تم مناداته أربع مرات فإنه يجب أن يظهر في أربع ) open Subroutine(لو نفس لذلك

مختلفة في البرنامج الرئيسي،أماآن

- closed subroutineيوجد مع هذا النوع من ، يمكن أن يخزن خارج البرنامج الرئيسي

:البرامج الفراعية مطلبين هما

البرنامج الرئيسي يجب أن ينفذ، -

closedحيث أن ) control and transfer of data(والثاني يجب نقل للـ -

subroutineيجب أن بحمل بالذاآرة في عنوان خاص .

• Relocating loaders perform four functions:

1- Allocate space in memory for the programs (allocation).

2- Resolve symbolic references between object decks (linking).

3- Adjust all address-dependent locations, such as address constants

with the allocated space (relocation).

4- Physically place the machine instructions and data into memory

(loading).

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Macros

The macro processor treats the identical parts of the program

defined by the abbreviation as a macro definition and saves the

definition.

After that, the macro processor substitutes the definition for all

occurrences of the abbreviation (macro call) in the program.

Compilers

A compiler is a program that accepts a program written in a high

level language and produces an object program.

An interpreter is a program that appears to execute a source

program as if it was machine language.

Machine Structure

- The CPU consists of an instruction interpreter, a location counter,

an instruction register and various working registers and general

registers.

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- The instruction interpreter is a group of electrical circuits (H.W.)

that perform the intent of instruction fetched from memory.

- The Location Counter (LC), also called Program Counter (PC) or

Instruction Counter (IC), is a hardware memory device which

denotes the location of the current instruction being executed.

- A copy of the current instruction is stored in the instruction register

(IR).

- The Memory Address Register (MAR) contains the address of the

memory location that is to be read from or stored into.

- The Memory Buffer Register (MBR) contains a copy of the

designated memory location specified by the MAR after a “read”

or the new contents of the memory location prior to a “write”.

- The memory controller is hardware that transfers data between the

MBR and the core memory location the address of which is in the

MAR.

- The I/O channels may be thought of as separate computers which

interpret special instructions for inputting and outputting

information from the memory.

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.تعمل) machine structure(لشرح آيف أن هذه المكونات للـ

عامة وهم بالنظام registersيملك أربعة ) SC-6251(على سبيل المثال الكمبيوتر نوع

بالشكل ) basic instruction(، حيث تكون )and 11 ,10 ,01 ,00(الثنائي آما يلي

:التالي

Memory Location

Register Number

Operation Code

(op) (reg) (addr)

For example, the instruction:

ADD 2, 178

Memory Location ( 178( المحفوظة في Dataإضافة

).general register 2(إلى محتوى

).Register 2(ونتيجة الجمع سوف تحفظ آقيمة جديدة للـ

Figure 2.1 يوضح )General machine structure (لمكاينة نوعها

(IBM system 1360).

- I/O channel تستخدم إلدخال المعلومات أو طبعها من memory.

- Memory controller هو الذي يقوم بنقل المعلومة بين MAR, MBR.

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- MAR تحتوي على العنوان للـ memory locationلتقرأ منه أو يخزن إليه .

- MBR تأخذ نسخة MAR بعد القراءة أو المحتويات الجديدة للـ ML عشان تجهيزهم

.لكتابة

- LC يكون وحدة من Mالتي تشير إلى مكان معلومة .

- IRيخزن به نسخة من المعلومة العامة .

- Instruction interpreter عبارة عن مجموعة من الدوائر الكهربية )H.W..(

Figure 2.2 يشرح الخطوات للـ )hardware operations ( المكونة داخل)the

instruction interpreter ( لتنفيذan instruction.

• MAR<= IC: - instruction counter يحدد location للـ current instruction

.MARفي

• IR<= MAR:- يضع instruction من MAR في IR.

.الباقي واضح •

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