The Architecture of Computer hardware, systems software & networking

The Architecture of Computer hardware, systems software & networking.



An Overview of Computer Systems

Chapter 1: Computers and Systems


Computer Architecture and Hardware operation

Chapter 2: Little Man computer

Chapter 3: CPU and Memory

Chapter 4: CPU and Memory Design Enhancement and Implementation

Chapter 5: Modern Computer systems


Network and Data Communications

Chapter 6: Overview of Network and Data Communications

Chapter 7: Ethernet and TCP/IP networking

Chapter 8: Communication Channel Technology


Software component

Chapter 9: Operating Systems Overview

Chapter 10: The user view of Operating systems

Chapter 11: Internal Operating Systems




An Overview of Computer Systems

Chapter 1: Computers and Systems

1.     Web Browser Application

The user uses the mouse pad to click on the browser URL and a page request message is sent via HTML through the communication channel till it reaches the web server.

2.     Input-Process-Output Model (IPO)

2.1 Input is the use of the keypad, mouse, scanner or punch cards

2.2. Processing is the use of the CPU executing the particular computer program

2.3 Output is via a printer, scanner or fax machine

2.4 Storage is through the hard drive, optical media discs or magnetic tape

3. Computer System Layout

3.1 The Internet consists of the web server, Data base server, Apps server and Web Browser which all goes through a firewall.

3.2 Order Fulfilment which involves warehousing, inventory, purchasing and shipping

3.3 Sales which consist of order entry, services, web design, and support.

3.4 Finance including financial planning, accounts payable, accounts receivable,  accounting and credit.

3.4 Marketing that includes research planning, advertising and sales.

4. Computer System Components

4.1 Hardware which provides input and output, controls input and output storage components and process data by executing instructions

4.2 Software gives the hardware instructions on what to do

4.3 Data is the representation of facts

4.4 Communications shares data and processing between systems


Computer Architecture and Hardware operation

Chapter 2: Little Man Computer

Created by Stuart Madnick, the Little Man Computer (LMC) is programmed in decimal code not binary code. It contains 100 mailboxes (memory) and each mailbox has 3 digit data. There is also an input and output box at the ends for sending and receiving data. Data is loaded into the mailboxes and then signals Little Man to start executing the information.

The execution program is as follows:

1.     Look for the number mailbox that contains the instruction

2.     Collect the instruction

3.     Set the program counter to receive the next instruction

4.     Decode the instruction

5.     Collect data with number found in previous step

6.     Execute the instruction

7.     Store new data in the mailbox from where the data was collected

8.     Stop or repeat the cycle

The Calculator

1.     Decimal keypad

2.     Addition and Subtraction keys

3.     3 digit display

4.     Result indicator

Instruction Codes Table

Copy number from mailbox with number (xy) to calculator
Replace the number in the mailbox at (xy) with current calculator value
Add the value in the mailbox at (xy) to calculator
Subtract the value in the mailbox at (xy) from the number in the calculator
Copy the number in the input basket to the calculator
Copy the value of the calculator to the output basket
Stop processing
Skip the next instruction if number is negative
Skip the next instruction if number is zero
Skip the next instruction if the number is positive
Re-set counter to (xy)


Chapter3: CPU and Memory

CPU (Central processing unit)consists of:

3.1 ALU: (arithmetic/logic unit)

The ALU arithmetic and logical instructions are executed via circuitry. It performs simple mathematical equations addition, subtraction, multiplication and division. The logical operation is usually a comparison that is equal to, less than or greater than concepts.

3.2 CU: control unit

This contains circuitry that uses electric signals that instructs the whole computer to execute messages. It controls the ALU and Memory.

3.3 Interface Unit

This moves data between the CPU and other hardware. The BUS is a bundle of wires that help carry signals between components.

Memory is the short term storage for CPU calculations and data.

Primary Storage, Main Memory, Internal Storage and RAM (random access memory) are other names for memory. Memory works with the CPU but is a separate entity. It only stores information as long as the program is in operation. Memory allows faster access to the required information.

Some examples of memory are:

1.     Ram

2.     Rom

3.     Cache

4.     Dynamic Ram

5.     Static Ram

6.     Flash Memory

7.     Memory sticks

8.     Virtual Memory

9.     Video Memory

10.  BIOS

Chapter 4: CPU and Memory: Design, Implementation, and Enhancement

4.1  CISC and RISC Architectures

CISC (Complex Instructions set computer) allows for complex instructions and requires many clock cycles to execute

RISC (Reduced Instruction set computer) reduces memory access by registers and simplifies instructions

4.2  VLIW and EPIC Architectures

VLIW (very long word instructions) based on 128-bit instructions called Molecule which is divided into 4 32-bit atoms. You cannot write programming in VLIW.

EPIC (Explicitly Parallel Instruction Computer) designed by Intel for IA-64 processors. Sequences are the responsibility of the programmer.

4.3  Memory enhancements.

Cache Memory is not visible to the user and is set between CPU and main Memory. It is high speed memory. Pentium III provides 2 levels of cache.

Memory interleaving is a method of dividing memory into several parts

Wide Path Memory Access provides for bigger bus data and a larger register between CPU and Main Memory.

4.4  Modern CPU processing enhancements

Timingis the process of synchronising the fetch to execute steps to the system clock pulses. The clock controls when the next step will take place. Multiprocessing increases performance

Pipelineimproves CPU performance by allowing overlapping of instructions. There are two types of Pipeline, Scalar processing and Superscalar processing.

Scalarprocessing is a pipeline method where only one command can be executed at a time. It divides the CPU into three main parts, the instruction fetch unit, and the instruction decode unit and the Instruction Execution method.

Superscalarprocessing is a pipeline method where more than one command can be executed at the same time; containing several execution units it can complicate the CPU.

Out of Order processing where a later instruction may depend on the result of an earlier instruction. Hazard and dependency is therefore corrected.

Branch Processing processes ahead of subsequent instructions.

Conflict Resources occur when instructions are executed in parallel and are using the same set of registers.

4.5   CPU implementation

CPU are implemented in 2 ways, Conventional Hardware implementation and Micro-programmed implementations. Conventional Hardware implementation executes virtually every instruction. Fast instructions are executed. However a disadvantage is that is a complex CPU hardware design.


Chapter 5: Modern Computer Systems

In 1937 the MARK 1 is built, it used electric relays. ABC was then built in 1939 and was the first electric computer using vacuum tubes. In1943-1946 the ENIAC was the first general purpose digital computer. In 1945 the Von Neumann architecture proposed was created and is still the standard for modern day computers. The transistor was created in 1947. In 1952 the EDVAC and IAS was made. Early computers were controlled by using switches for each bit but had no operating systems. Operating systems were first built in 1954 by General Motors Research Laboratory for their IBM 701 computer. Other early operating systems were FMS (Fortran monitor system), IBSYS and SOS (shared operating system)

UNIX then came on to the scene and used assembly language and developed a hierarchical file system, the shell system, document formatting and tools for processing.

GUI ‘s changed modern computer systems further when Doug Englebart, of the Stanford Research institute invented windows and a mouse interface in the 1960’s ,in the 1970’s Xerox PARC creates a windowing system for the Dynobook project.  Then Steve Jobs made history in the 1980’s by developing Apple and Macintosh.


In 1982 the first stand alone personal computer was created using disk operating system MS –DOS, and PC-DOS, then later new versions of DOS were added with hierarchical file storage and file redirection.




Network and Data communications

Chapter 6: Overview of Network and Data Communications.

Data Communication refers to the sending and receiving of data between 2 computers and communication between a computer network and a data network. This connection is achieved via cable or wireless devices. The internet is a computer network. A system of different networks all connected to or to each other or to network peripherals such as a printer. This facilitates sharing of information. 


Chapter 7: Ethernet/IP Networking

Ethernet is an industrial Ethernet Network that mixes Ethernet technology with different (CIP) Common Industrial Protocols. It transfers I/O via UDP (User Datagram Protocol). Messaging, uploading and downloading via TCP. Change of state monitoring via UPD. It uses unicast, multicast and broadcast settings and making use of PORT numbers for messaging.

In Network Architecture there can be one or more systems acting as Server. The client then makes a request from the Server. The Servers take and process request. The systems work at the same level called peers and work in a point to point connection.  There can also be a mis which involves using both types.


Chapter 8: Communication Channel Technology

The communication channel is characterised by signal method, bandwidth which is the amount of data transmitted, direction in which the signal can flow, noise characteristics, and medium used.

Signalling transmission is divided into analogue and digital. Analogue uses waveforms to carry data and digital uses electrical volts, currents or on/off switches.

Point to point transmission via simplex, half-duplex of full-duplex. Simplex passes data through one channel, half-duplex transmits in one direction at a time and full-duplex transmits in both directions at the same time. Multipoint transmissions message to all connected receivers. Multiplexing carries many messages at once. Wireless networks, telephones, microwave communications, radio and sound are analogue signals.


Software component

Chapter 9: Operating Systems Overview

The operating system is the software that manages the computer hardware. Its purpose is to provide and provide a efficient way for the user to execute programs. The hardware must be compatible with the appropriate software. It controls the execution on an application. The operating system is a set of programs that run the computer. It performs tasks such as recognise input from the keyboard and keeping track of files. It controls the use of the system resources between user and task. An interface between the programmer and the hardware that enables easy coding

In 1962 MIT Project Mac creating a time sharing Operating System called CTSS and shortly after that Multics was developed. In1963 Burroughs developed the MCP (Master Control Program) that included many of the operating system features used today. In 1964 OS/360 was developed by IBM and it included batch processing of programmes.

Chapter 10: The user view of Operating systems

This is the external view of the Operating System and is the layer of software on top of the hardware. The user view varies by the interface being used. The operating system is designed for ease of use and free resource use. Most users make use of a monitor, keyboard, mouse and a system unit. Users sit at a main frame or Personal computer.

Chapter 11: Internal Operating Systems

Internal Operating systems modify programs and data files and provide access to the user for translating the program and provide a program to move the code to the computer’s memory. It also provides the platform to handle the I/O programming details. The resource manager that controls and managed the CPU, Memory and i/o devices.


The I/O traffic controller keeps track of the devices. Each I/O device has a different handler. The I/O subsystem consists of buffering and cache in the memory component and and device driver interface.

11.1 The Assembler

The Assembler input provides an assembly language program while the output provides an object program for executing commands and contains the information the programmer needs to perform the task.

11.2 The Compiler

The Compiler processes high level languages such as COBOL, ALGOL, PL/I and FORTRAN. A compiler is a source code that produces a corresponding object. An interpreter is the program that appears to change the source code.

11.3 The Loader

A loader prepares an object program for execution with a load. There are a number of loading schemes; absolute, direct linking and relocating. The loader will load, then relocate and then link the object program. It puts programs into memory to get them ready for execution. The assembler outputs the machine language translation of a program to another device in a simple loading system and a loader is placed in the centre. The loader puts the machine language of the users’ program into memory and gives it the control. The loader program is much smaller than the assembler and thus provides more available space for the users program