TOPIC 1: COMPUTER SYSTEM
1) HISTORY OF COMPUTING
Definition of a Computer
- Before 1935
a computer was a person who performed
arithmetic calculations
arithmetic calculations
- Between 1935 and 1945
the definition referred to a machine, rather
than a person
than a person
- The modern machine definition is based on von Neumann's concepts: a device that accepts input, processes data, stores data, and produces output.
Computing milestones and machine evolution
Divide into two : 1) Before 1940
2) After 1940
2) After 1940
1) Before 1940
- 14th C. - Abacus - an instrument for performing calculations by sliding counters along rods or in grooves
- 17th C. - Slide rule - a manual device used for calculation that consists in its simple form of a ruler and a movable middle piece which are graduated with similar logarithmic scales
- 1642 - Pascaline--a mechanical calculator built by Blaise Pascal, a 17th century mathematician, for whom the Pascal computer programming language was named
- 1804 - Jacquard loom - a loom programmed with punched cards invented by Joseph Marie Jacquard
- 1850 - Difference Engine -Charles Babbage
2) After 1940
First Generation (1940-1956 )
- used vacuum tubes for circuitry and magnetic drums for memory
- very expensive to operate
- to using a great deal of electricity, generated a lot of heat
- Examples:
- UNIVAC
- ENIAC
- ENIAC
Second Generation (1956-1963 )
- Transistors replaced vacuum tubes
- many high level programming languages were introduced, including FORTRAN (1956), ALGOL (1958), and COBOL (1959)
- commercial machines of this era include the IBM 704 and its successors, the 709 and 7094
Third Generation (1964-1971 )
- Integrated circuits (IC) (semiconductor devices with several transistors built into one physical component) based on technology
Fourth Generation (1972-1984)
- use of large scale integration (LSI - 1000 devices per chip) and very large scale integration (VLSI - 100,000 devices per chip)
- using microprocessors
- the development of the C programming language and the UNIX operating system
Fifth Generation (1985-beyond)
- based on artificial intelligence
- widespread use of computer networks and the increasing use of single-user workstations
BASIC COMPUTER SYSTEM
A computer system is the combination of hardware and software. A typical computer system has memory and set of states that define the relationship between the system's inputs and outputs
WHAT IS A COMPUTER?
A COMPUTER is an electronic device, operating under the control of instructions stored in its own memory, that can accept data, process the data according to specified rules, produce results, and store the results for future use.
BASIC COMPUTER COMPONENTS
1) COMPUTER HARDWARE
is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware.
MAJOR HARDWARE COMPONENTS OF A COMPUTER SYSTEM ARE:
- Main Memory - Secondary memory
a) INPUT DEVICES - An input device is any hardware component that allows you to enter data and instructions into a computer. Example of input devices :
b) CENTRAL PROCESSING UNIT (CPU) - The “BRAIN" of the computer - performsprocessing functions . It is composed of 2 major components: a. the Control Unit and b. the Arithmetic Logic Unit (ALU). - CPU is contained on a single chip called a microprocessor also known as an integrated circuit . - The speed of a microprocessor is determined in clock speed, which is measured in megahertz ( MHz), millions of cycles per second - The higher the faster. ex. 2 GHz Pentium i) Control Unit - charge of the activities of the CPU. It basically directs or tells the computer what to do. - known ascomputer police traffic. ii) Arithmetic Logik Unit (ALU) - the component of the CPU that performs arithmetic and logical operations. - ALU can performs four kinds of arithmetic operations : addition, subtraction, multiplication and division. - A logical operation is usually a comparison a) MEMORY UNIT n also known as main memory, primary memory, or internal storage n There are two types of chips that take care of a computers internal memory: i) ROM ii) RAM i) ROM Chips – Memory - ROM is read only memory - ROM is nonvolatile memory because it does not disappear when the computer is turned off - ROM chips store information permanently in the computer's memory, this information supplies the computer with a list of operating instructions - It contains software that is required to make your computer work with your operating system ii) RAM Chips – Memory - RAM is random access memory - Information on RAM chips can be modified - Users can read, write, and erase its information - RAM is known as volatile memory because it is temporary - When an individual turns off the computer, he loses the information in RAM. RAM, also known as main memory, is the "working memory" of the computer - Its temporary storage - It stores program data while we are working with that program - A program must be loaded into RAM in order to work - Computers typically now come with 16 MB (megabytes) of RAM. The more MB, the better. STORAGE DEVICES n also known as secondary memory or secondary storage n Storage holds data, instruction and information for future use. n Examples of storage media
i) STORAGE DEVICES - Floppy Disks - A floppy disk is a thin magnetic-coated disk contained in a flexible or semi-rigid protective jacket. Data is stored in tracks and sectors. - The floppy disks are usually 3.5" in size. However, older floppy disks may be in use; these would be 5.25" in size. - Double sided high density 3.5" disks can hold 1.44 Mb of data. - Once data is stored on a floppy disk it can be 'write protected' by clicking a tab on the disk. This prevents any new data being stored or any old data being erased. ii) STORAGE DEVICES – Hard Disks - The hard disk is a direct-access storage medium with a rigid magnetic disk. - The data is stored as magnetised spots arranged in concentric circles (tracks) on the disk. - Each track is divided into sectors. The number of tracks and sectors on a disk is known as its 'format'. - The storage capacity of a hard disk can be Gigabytes (Gb), i.e. thousands of Megabytes (1000Mb), of information iii) STORAGE DEVICES - Magnetic Tape - A recording medium consisting of a thin tape with a coating of a fine magnetic material, used for recording analogue or digital data. Data is stored in frames across the width of the tape. The frames are grouped into blocks or records which are separated from other blocks by gaps - Magnetic tape is a serial access medium, similar to an audio cassette, and so data (like the songs on a music tape) cannot be quickly located. - However large amounts of information can be stored within magnetic tape. This characteristic has prompted its use in the regular backing up of hard disks. iv) STORAGE DEVICES - Disks An optical disk is impressed with a series of spiral pits in a flat surface. A master disk is burnt by high-intensity laser beams in - bit-patterns from which subsequent copies are formed which can be read optically by laser. - The optical disk is a random access storage medium; information can be easily read from any point on the disk. A standard CD-ROM can store up to 650Mb of data, with 14,500 tracks per inch (tpi). - CD-ROM stands for Compact Disk - Read Only Memory. It is now possible to have CD-ROMs where extra tracks of information can be written onto them by the user. These are called read/writable CD-ROMs and these are becoming a popular and cheap method for storage. a) OUTPUT DEVICES - An output device is any hardware component that conveys information to one or more people. - An output device is used to send data out of the system. - Example of output devices :
Advantages of Using Computers
 When data, instructions and information flow along electronic circuits, they travel at incredibly fast speeds. Many computers process billions or trillions of operations in a single second.
The electronic components in modern computers are dependable and reliable because they rarely break of fail
Given the same input and processes, a computer will produce the same results – consistently.
Can transfer data quickly from storage to memory, process it, and then store it again for future use.
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