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software engineering first year
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- HISTORY OF COMPUTERS........................................................................................................................................ - GENERATION OF COMPUTERS................................................................................................................................ - Computer generations - CHARACTERISTICS OF COMPUTERS................................................................................................................... - BASIC COMPUTER CONCEPTS............................................................................................................................. - TYPES OF COMPUTERS - SOFTWARE AND HARDWARE - CHAPTER REVIEW QUESTIONS Purpose of the course To provide an in-depth presentation of computer hardware and software with more emphasis on the more technical aspects of computing such as troubleshooting and upgrading computers.
I. Introduction to Computer and its components A. History of computers B. Generations of computers C. Characteristics of computers D. Types of computers E. Software and Hardware
II. Hardware and software A. Hardware: input and output devices, backup storage, central processing unit, memory (ROM, RAM). B. Software: Categories of software, System software, applications software, general purpose software, integrated packages and software suites.
III. Inside the computer A. The processor; Arithmetic and Logic Unit, Control Unit, system clock, registers B. The fetch execute cycle C. The motherboard; form factor, sockets and slots D. Buses; control bus, data bus, Address Bus, SCSI, EISA, MCA
IV. Fault Diagnosis A. Power Supply Troubleshooting B. Video Failure Troubleshooting C. Motherboard and CPU Troubleshooting D. Hard Drive Failure Troubleshooting
V. Input and output devices and interrupts. A. Output devices B. Input Devices C. Interrupts; types of interrupt, interrupt priorities, interrupt handler
Computer architecture or digital computer organization is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit (CPU) performs internally and accesses addresses in memory.
It may also be defined as the science and art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals.
Computer architecture comprises at least three main subcategories:
Instruction set architecture, or ISA, is the abstract image of a computing system that is seen by a machine language (or assembly language) programmer, including the instruction set, word size, memory address modes, processor registers, and address and data formats.
Microarchitecture, also known as Computer organization is a lower level, more concrete and detailed, description of the system that involves how the constituent parts of the system are interconnected and how they interoperate in order to implement the ISA. The size of a computer's cache for instance, is an organizational issue that generally has nothing to do with the ISA.
System Design which includes all of the other hardware components within a computing system such as:
Objectives At the end of the chapter the learner shall be able to; i. Explain the evolution of computing technology and the technological advancement in computer architecture to current technologies ii. Explain the characteristics of computers and how they are different from humans. iii. Explain the different types of computers categorized based on size, price and capabilities iv. Explain the fundamental difference between computer hardware and software
1.1. History of Computers
When the human race started doing some trade, it felt a need for a calculating device. The first calculating device, which was used 2000 years ago was called abacus and the improvements in the calculating device in that age were slow. The next change came after about 1600 years. Following this, the changes were frequent and the mechanical desk calculator was developed around 1800 A.D.
In 1833, Prof. Charles Babbage, the father of the computer, developed a machine called analytical engine which was the vase for the modern digital computer.
1.2 Generation of Computers
1.2.1 Computer generations
First generation computers (1946-1956) They made use of vacuum tubes to store and process information. The tubes consumed a lot of power and generated a lot of heat (overheating). They were huge in size and occupy a room. They used magnetic tape. Storage capacity was very low i.e. 2kb and speed of processing was also very low. First machine in this category was ENIAC (electronic discrete variable automatic computer) and later came UNIVAC (universal automatic computers).these computers were mostly computational machines. Their input /output capabilities were usually limited to the keyboard and or punched card input and printer and or punched cart output. The speed of these machines was described in milliseconds (1/1000 of a second)
Second generation computers (1957-1967) These computers used transistors after invention of transistors. The transistor is smaller cheaper and produced less heat than vacuum tubes and consumed less power. The cost of computers decreased and the speed increased. The second generation saw the introduction of more complex ALU and CPU, the use of high level languages and provision of system software with the computer. Data access time was measured in micro-seconds. Removable disk storage units were
o Number of components in computer per circuit (IC) greatly increased over 500,000 physical elements e.g. transistors, capacities, diodes etc per chip(IC).
1.3 Characteristics of Computers
1.4 Basic Computer Concepts
Definition of a computer
A computer is an electronic device capable of executing instructions, developed based on algorithms stored in its memory, to process data fed to it and produce the required results faster than human beings.
The definition from the Merriam-Webster Dictionary :
"one that computes; specifically : a programmable electronic device that can store, retrieve, and process data"
1.5 Types of Computers
What different types of computers are there? This categories are based on size, price and capabilities
Super computers
They are very large in size and use multiple processors and superior technology. Super computers are biggest in size, the most expensive in price than any other is classified and known as super computer. It can process trillions of instructions in seconds. This computer is not used as a PC in a home neither by a student in a college. Governments specially use this type of computer for their different calculations and heavy jobs. Different industries also use this huge computer for designing their products.
In most of the Hollywood’s movies it is used for animation purposes. This kind of computer is also helpful for forecasting weather reports worldwide. They are known for von Newman’s design i.e. multiple processor system with parallel processing. In such a system a task is broken down and shared among processes for faster execution. They are used for complex tasks requiring a lot of computational power.
Mainframe computers A mainframe is another giant computer after the super computer and can also process millions of instruction per second and capable of accessing billions of data .They are physically very large in size with very high capacity of main memory. This computer is commonly used in big hospitals, air line reservations companies, and many other huge companies prefer mainframe because of its capability of retrieving data on a huge basis. They can be linked to smaller computers and handle hundreds of users they are also used in space exploitation. The term mainframe was mainly used for earliest computers as they were big in size though today the term is used to refer to large computers. A large number of peripherals can be attached to them. They are expensive to install.
Minicomputers They are smaller than the main frame but bigger than minicomputers. They support concurrent users. They can be used as servers in companies. They are slower and less costly compared to mainframe computers but more powerful, reliable and expensive than micro computers.
Micro computers They are of advanced technology i.e. the micro era based on large scale integration that confines several physical components per small elements thumb size IC, hence the size reduced. It is the smallest of the three computers. They are usually called personal computers since they are designed to be used by individuals. The micro chip technology has enabled reduction of size of
Computer software A set of programs associated with the operation of a computer
The two components (hardware, software) will be discussed later in other chapters.
1.7 Chapter Review Questions
Suggested Readings
At the end of the chapter the learner shall be able to; Explain the different hardware units of a computer system such as input, output, Central processing unit (CPU), main memory and secondary storage Explain how the different units of a computer interact witch each other to give the user output Explain how information is stored in a computer Explain the different storage units of a computer such as byte, Kilobyte, megabyte, Gigabyte and Terabyte
Hardware units (Devices) of a computer can be categorized into five units; I. Input unit II. Output III. Central processing unit (CPU) or processor IV. Main Memory V. Secondary storage/Backing Storage
2.1 Input Devices
An input device lets you communicate with a computer. They are used to enter information and issue commands to the computer. Commands tell the computer to do something, like save the file. A keyboard, mouse, scanner, digital camera, touch pads and joystick are examples of input devices. o Keyboard Used to type data into the computer. It has special keys for giving the computer commands called command or function keys o Pointing Devices Pointing devices move some object on the screen and can do some action Mouse is a common pointing device o Scanner allows you to scan documents, pictures, or graphics and view them on the computer. You can also use software to edit the items you scan. Used to put printed pictures and text into a computer. It Converts an image into dots that the computer can understand .To scan text, optical character recognition (OCR) software is needed o Digital Camera Used to take electronic pictures of an object. The pictures taken by a digital camera can be used directly by a computer o Microphone Used to put sound into a computer. Need sound recording software o Video Capture Card Usually place inside the computer's case. Use to put video into a computer. Need a video source, either a video camera or video recorder o Voice input device- A computer I/O device in which vocal commands may be entered into a computer system.
o Speakers Used to output sound o LCD Projectors Similar to monitors but projects an image on to a screen. They are mainly used for presentations.
2.3 Central Processing Unit (CPU)/Processor:
It is the main part of a computer system like the brain of a human being. It interprets the instructions in the program and executes one by one. The CPU of a microcomputer is called a microprocessor. Central Processing Unit is implemented in a single piece of silicon device known as a computer chip.
The processor and main memory of a PC are commonly held on a single board called a mother board. The processor has the following functions:
It controls the transmission of data from input devices to memory;
It processes the data held in main memory;
It controls the transmission of information from main memory to output devices.
The processor contains the control unit and the arithmetic/logic unit(ALU).
The control unit coordinates and controls all the operations carried out by the computer. The control unit operates by repeating three operations which are:
Fetch – cause the next instruction to be fetched from memory; Decode – translate the program instruction into commands that the computer can process Execute – cause the instruction to be executed
The arithmetic/logic unit(ALU) plays two roles.
Arithmetic operations – these operations are addition, subtraction, multiplication and division.. Logical operations – it compares two data items to determine whether the first one is smaller than, equal to or greater than the second item.
2.4 Main Memory:
The cycle (input - processing - output) would not be possible without a holding place for the instructions and data that the processors (CPU) can easily reach. This holding place is known as memory also called main storage and is internal to the computer consisting of RAM and possibly ROM.
Random Access Memory ( RAM)
Is the basic kind of internal memory that holds data and instructions while the computer is in use. It can be read from and written to. It is called random access because the processor or computer can access any location in memory in any order as contrasted with sequential access devices which must be accessed in order. RAM is volatile; losing the stored information in an event of power loss, and quite expensive.
There are two basic types of RAM. Static RAM does not need to be refreshed, which makes it faster; but it is also more expensive than dynamic RAM. Dynamic RAM needs to be refreshed thousands of times per second. Both types of RAM are volatile, meaning that they lose their contents when the power is turned off.
Over the years, newer computers have been introduced that contain faster microprocessors. To accommodate the increased speed, chip manufacturers have designed and built faster RAM chips. SDRAM (Synchronous DRAM) divides RAM into two separate memory banks to increase the processing of the memory requests. To overcome the performance limitations of SDRAM, two competing technologies have been developed. RDRAM (Rambus DRAM) involves a new memory design that achieves a higher data transfer speeds but it is expensive to manufacture. DDR SDRAM (Double Data Rate SDRAM) can transfer data twice as fast as SDRAM because it reads data twice during each clock cycle. Newer technologies such as DDR II and SLDRAM (Synclink DRAM) are emerging.
ROM (Read only memory) Is also random access but only for reads, once data has been written onto a ROM chip, it cannot be removed and can only be read. It refers to special memory used to store programs that boot the computer and perform diagnostics. Most personal computers have a small amount of ROM (a few thousand bytes). Retains its contents even when the computer is turned off and is therefore referred to as being nonvolatile.
Cache Memory
Processor
Main Memory
compared to real read-write memory (RAM) where rewriting is done often many times per second!
Cache memory After Random Access Memory ( RAM) Cache memory is a type of very fast memory that is used to improve the speed of a computer doubling it in some cases. It acts as an intermediate store between the CPU and the maim memory, and works by storing the most frequently or recently used instructions and data so that it will be very fast to retrieve them again.
2.5 Secondary storage
These are devices which are used to store huge information for future use. This is
mostly hard drives and removable media such as floppy disks, optical media
(CD ROM) etc.
Hard Drive: Floppy Disk: Floppy disks allow information to be transported easily from one computer to another they have limited storage capacity, generally 1.44 MB. Saving and retrieving information from a floppy disk is slower than on a hard drive. They are more susceptible to physical damage and viruses than the hard drive. The size of a hard drive is usually expressed in terms of megabytes and gigabytes.
Processor
Main Memory
Output Devices
Input Devices
Secondary/Backing Storage
Compact Disk Read Only Memory (CD ROM): CD ROMs are read only storage medium. Typically, a CD ROM holds up to 650 MB of information. While information retrieval is faster than from a floppy disk, it is still not as fast as from the hard drive.
Compact Disk-Writable (CD-R): A CD-R is highly effective for storing a large amount of data. Can hold up to 700MB of information. A CD-R is a one time recordable compact disc. Compact Disk-Re-Writable (CD-RW): A CD-RW allows you to read, write, erase and write again. Writing takes place in a single pass of the focused laser beam. This is sometimes referred to as direct overwriting and can be repeated several thousand times per disc.
2.6 Computer units interaction diagram
The diagram above shows how the units interact with each other in the processing of data. Input devices enter information to be processed by the processor. The processor can read and write into the secondary storage devices.
The processor also stores the instructions being currently executed into the main memory. So can be able to read and write into the main memory (RAM). Once the data has been processed by the processor, the data can be displayed by the output devices. Please note the direction of the arrows as it depicts the flow of the data and instructions.