Download Basic Computer Organization and more Study notes Computer science in PDF only on Docsity!
BASIC COMPUTER ORGANIZATION:
▲ A computer is an information processing machine. It can be viewed as a system, which consists of number of interrelated components that work together with the aim of converting data into information. ▲ To attain information, data is entered through input devices. ▲ This data is processed using the central processing unit and then the processed data is displayed to the users using various output devices. ▲ All these parts (input devices, central processing unit and output devices) are referred to as hardware of the computer. ▲ The block diagram of the computer system have the following three units, each functional unit corresponds to their basic operations performed as described in detail
- Input Unit
- Central Processing Unit
- Output Unit
INPUT DEVICES:
▲ Input devices are electromechanical devices that allow the user to feed information into the computer for analysis, storage and to give commands to the Central Processing Unit. ▲ Data and instructions are entered into the memory of a computer through input devices. ▲ It captures information and translates it into a form that can be processed by the central processing unit. ▲ Computer accepts input in two ways, either manually or directly. ▲ In case of manual data entry, the user enters the data into the computer by hand. For example, by using keyboard and mouse.
▲ It controls and co-ordinates the entire computer system. ▲ The input unit does not know when to receive data and where to put the data in the storage unit after receiving it, control unit gives necessary instructions to the input unit. ▲ Similarly the control unit instructs the input unit where to store the data after receiving it from the user. ▲ In same way it controls the flow of data and instructions from the storage unit to ALU. ▲ It also controls flow of results from ALU to storage unit. ▲ Also controls what should be sent to the output unit.
ARITHMETIC / LOGIC UNIT (ALU):
- The arithmetic / logic unit (ALU) contains the electronic circuitry that executes all arithmetic and logical operations on the data made available to it.
Arithmetic Unit:
- This unit is responsible for performing the actual computing and carrying out the arithmetic calculations such as addition, subtraction, multiplication and division.
- It can perform these operations at a very high speed.
Logic Unit:
- The logic unit enables the CPU to perform logical operations based on the instructions provided to it.
- The unit can compare numbers, letters or special characters and can then take action based on the result of the comparison.
- Logical operations of logic unit can test for three conditions : (1) equal – to condition, (2) less than condition, (3) greater than condition.
MEMORY UNIT:
▲ Computers require memory to process data and store output. Memory refers to the electronic holding place for instructions and data. ▲ We can classify memory into two broad categories:
- Primary memory (to handle the data)
- Secondary memory (to store) Primary Memory: (Volatile Memory) ▲ Primary memory, also known as main memory stores data and instructions for processing.
▲ This is generally used to hold the program being currently executed in the computer, the data being received from the input unit and the intermediate and final results of the program. ▲ The primary memory generally loses its contents when you switch off the computer. Secondary Memory: (Non – Volatile Memory)
▲ It may store several programs, documents, databases, etc ▲ Secondary memory, also known as auxiliary memory or external memory is used for storing instructions and data. ▲ It is the permanent storage. The data or information stored in this storage will not be erased when the power is lost. It is a non – volatile memory.
OUTPUT DEVICES:
▲ Devices used to get the response or result of a process from the computer is called output devices. ▲ Output devices take the machine coded output results from the CPU and convert them into a form that is easily readable(such as characters, graphical, or audio visual) by human beings. ▲ The outputs which can be easily understood and used by human beings are in the form of hard copy and soft copy. ▲ The physical form of output is known as hard copy. ▲ The electronic version of an output, which usually resides in computer memory and disk, is known as soft copy. ▲ Commonly used output devices are: Visual Display Unit (VDU) or Monitor, Printers, Plotters, etc.
COMPUTER GENERATIONS:
The computer generation means step-by step growth in the technology. It is often used in relation to the hardware of computer.
Each phase of computer has been extended to include both hardware and software, together make up an entire computer system.
- Very high in size
- Occupies large space
- High heat production and high power consumption
EXAMPLES:
- EDSAC, EDVAC
- UNIVAC – I
- IBM 70
SECOND GENERATION COMPUTERS:
▲ The second generation computers replaced the basic electronic component vacuum tubes with transistors ▲ Transistor occupies less space and requires almost one – tenth of the power compared to the vacuum tubes. ▲ The second generation computers began with the advent of transistorized circuitry, invention of magnetic core and development of magnetic disk storage devices. They used assembly level programming languages and a better processing than the first generation. ▲ The stored program concept meant that instructions to run a computer for a specific function and could quickly be replaced by a different set of instructions for a different function. ▲ More sophisticated high level languages such as COBOL (Common Business Oriented Language) and FORTRAN (Formula Translator) came into common used during this time. ▲ These languages replaced binary machine code with words, sentences and mathematical formulae, making it much easier to program a computer. ▲ Batch processing ▲ Commercial applications rapidly developed during this period and more than 80% of these computers were used in business and industries in the applications like payroll, inventory control, etc. ADVANTAGES:
- Small in size
- Computational time in micro seconds
- Less heat generated
- Better speed and portability
DISADVANTAGES:
- Frequent maintenance required
- Manual assembly of individual components into a functioning unit was required.
EXAMPLE:
- IBM 1620 Small Scientific
- IBM 1401 Small to Medium Business
- IBM 7094 Large Scientific & Business
- RLA 501 Medium Business
- UNIVAC 1108 Large Scientific & Business
THIRD GENERATION COMPUTERS: ▲ Third generation computers were based on Integrated Circuits (ICs). The IC chips were made of silicon. ▲ (^) The small and medium scale Integrated Circuits replaced the transistors in the hardware, while semi – conductor memory elements replace the magnetic core memory. Magnetic disks fully replace the magnetic tapes as the storage medium. ▲ The ICs provided vast internal storage and increase the operational efficiency. ▲ Another concept developed during this period was an operating system and high level programming languages are used. – Time sharing.
ADVANTAGES:
- Small in size
- Computational time in Nano seconds
- (^) Less heat and less power required.
EXAMPLE:
EXAMPLE:
- Intel – 400 L
- IBM Compatible
- Apple Series I & II
FIFTH GENERATION COMPUTERS:
▲ Computers are machines that perform only when instructed. They may operate at fast speed and perform with unbelievable accuracy. But they are unable to act or think on their own. ▲ Human being is leading towards a stage, when an Artificial Intelligent machine could be developed which will even be in a position to think and decide. ▲ Recent Researchers are aimed at designing the logic for the thinking computers for building expert systems and knowledge base systems. ▲ The knowledge base system has a very large store of knowledge with a set of processors, which access and update it. ▲ The inference mechanism draws reasoned conclusions from the knowledge base, much of its processing will be drawing logical inference of the format :
- If < Condition > then < action> ▲ The intelligent user interface is the point of contact between a fifth generation computer and its user. The intention is to build a user interface which is close to the natural ways of thinking of the user rather than close to the way of working of the computer.
ADVANTAGES:
- More user friendly
- Supports newer and powerful application
- The super computers fall under this generation.
