Fundamental of computer.pdf

# 1. Fundamentals of Computer ## 1. Computer - An Introduction: The term Computer is used to describe a device consisting of a combination of electromechanical components. The machine which we usually see on a desk or which we imagine when the word computer is spoken is not the real or complete c...

# 1. Fundamentals of Computer ## 1. Computer - An Introduction: The term Computer is used to describe a device consisting of a combination of electromechanical components. The machine which we usually see on a desk or which we imagine when the word computer is spoken is not the real or complete computer. It is just the hardware of computer. A computer is often called a computer system because it is not one device or component. A computer System is the combination of, at least the following six elements: - Hardware: the machine parts of computer. - Software: the processing capability of hardware - People: the operators of computer; they create the software for computer. - Procedures: the set of instructions, which are used to carry out routine task to manage computer and files. - Data: the collection of facts and figures, which are to be processed by the computer. - Information: the result that we get after processing data under the given instructions. ## 2. Computer - Definition: It is difficult to give one clear-cut definition of computer, because different people define computer differently according to their usage of the machine. A general definition of computer can be: A Computer is an automatic electronic device, which can receive data from some input device, process it under the given instructions, and gives out the information through some output device. ## 3. Main Blocks of Computer: A computer consists of 3 main units: - Input Unit - Processing Unit - Output Unit ### Input Unit: It is the unit of a computer system, which provides a mean of communication between computer and outside world. The input unit takes in the data and instructions from a user and translate them into a form that computer can understand. Keyboard is the main input unit of a computer. ### Output Unit: It is the unit of a computer system that is used to show the results of processing (i.e. information) to the user. The results of processing are in the form of machine codes when they come out of the processing unit. The output unit converts these codes into a form, which can be directly understood by users or other peripheral devices. Visual Display Unit (VDU) in the main output unit of a computer. ### Central Processing Unit: Abbreviated as CPU, it is the main unit of a computer. It controls all the functions, actions, and processing done by a computer. The CPU controls and co-ordinates all the peripherals attached to a computer. The CPU has three main parts or sub units: - Control Unit (CU) - Arithmetic Logic Unit (ALU) - Memory Unit #### 6.1. Control Unit: Abbreviated as CU, the control unit controls and coordinates all activities of a computer. It includes: - Controls the Input-Output devices. - Storing and retrieving data from memory. - Storing and retrieving data from storage devices. - Routing of information between memory and ALU. - Controls the direction of arithmetic and logic operations. - Controls the execution of programs. #### 6.2. Arithmetic Logic Unit: Abbreviated as ALU, the Arithmetic and Logic Unit performs all arithmetic operations such as addition, subtraction, multiplication, and division of numeric data (i.e. numbers). This unit also performs the logical operations such as comparing two values to check if one is greater/smaller than the other or not. Similarly it can check a condition for true or false. #### 6.3. Memory Unit: It is the storage area of a computer where data, instruction, and information are stored. According to the usage, it is divided into two parts: - Random Access Memo (RAM) - Read-Only Memory (ROM). ##### 6.3.1. Random Access Memory (RAM): It is also called User's Memory. In RAM data and programs are held temporarily during the processing, which means that after one task is completed, these data and programs are erased and new items are placed in the RAM. Thus RAM is re-useable memory. RAM is also called volatile (i.e. unstable) memory because when the power is switched off, its contents get erased. The data held in RAM is instantly available to the computer. ##### 6.3.2. Read-Only Memory (ROM): It is used to hold programs/instructions that are required to "boot" a computer. These programs/instructions include certain start-up programs such as routine that start disk drives, load operating system into RAM (Bootstrap Program) and transfer of control to the newly loaded operating system. A user can't change the contents of ROM. These programs/instructions are stored on a ROM chip when it is manufactured. ROM is often called "firmware" because "software (programs) are permanently stored on hardware". ROM is also called non-volatile (i.e. stable) memory because its contents can't be destroyed; they remain there even when the power is switched off. ## 7. Block Diagram: The Block Diagram of a computer shows the path of data from Input Unit to Central Processing Unit to Output Unit. As shown in the figure (on the next page), CPU receives inputs (data/instructions) from the Input Unit by the Control Unit. The CU sends it to the memory Unit to store it. From there it is taken into the Arithmetic Logic Unit. In ALU data is processed under the given instructions (receives along with the data). The CU takes out the results of these processing and store these back in the Memory unit. The CU then takes out these results and sends them to the Output Unit for the users or other peripheral devices to use them according to their requirements. The memory contained in the CPU is called the Primary Memory (discussed in later chapter). The memory shown out of the block diagram is called Secondary Memory, which constitutes a part of a Computer System, but it is not a part of the CPU so it is drawn outside the CPU boundary. ## 8. Memory Measuring Units: Bit and Byte are the two basic units in which the memory of computer is measured. - A bit is the place required in computer's memory to store 1 binary digit. There are two binary digits; 0 and 1. - A byte is the group of 8 continuous bits that are required to store one character (alphabet) of human language in computer's memory. The bigger units in this series are (using denary values) – Kilo Byte(KB), Mega Byte (MB), Giga Byte (GB), Tera Byte (TB), Peta Byte (PB) and Exa Byte (EB). | Name of memory size | Number of bytes | Equivalent Denary value | |---|---|---| | 1 kilobyte (1 KB) | 10³ | 1 000 bytes | | 1 megabyte (1 MB) | 10⁶ | 1 000 000 bytes | | 1 gigabyte (1 GB) | 10⁹ | 1 000 000 000 bytes | | 1 terabyte (1 TB) | 10¹² | 1 000 000 000 000 bytes | | 1 petabyte (1 PB) | 10¹⁵ | 1 000 000 000 000 000 bytes | | 1 exabyte (1 EB) | 10¹⁸ | 1 000 000 000 000 000 000 bytes | Since memory size is actually measured in terms of powers of 2, another system has been adopted by the IEC (International Electrotechnical Commission) that is based on the binary system. The bigger units in this series are (using binary values) – Kibi Byte (KiB), Mebi Byte (MiB), Gibi Byte (GiB), Tebi Byte (TiB), Pebi Byte (PiB) and Exbi Byte (EiB). | Name of memory size | Number of bytes | Equivalent Denary value | |---|---|---| | 1 kibibyte (1 KiB) | 2¹⁰ | 1 024 bytes | | 1 mebibyte (1 MiB) | 2²⁰ | 1 048 576 bytes | | 1 gibibyte (1 GiB) | 2³⁰ | 1 073 741 824 bytes | | 1 tebibyte (1 TiB) | 2⁴⁰ | 1 099 511 627 776 bytes | | 1 pebibyte (1 PiB) | 2⁵⁰ | 1 125 899 906 842 624 bytes | | 1 exbibyte (1 EiB) | 2⁶⁰ | 1 152 921 504 606 846 976 bytes | They will be explained in a later chapter at an appropriate time. For the time being just remember their names and the relation between them as given in the tables. ## 9. Advantages of Computer: When it comes to the comparison between the manual work and the computerized work, we find that computer scores over man on the following points: - **Speed:** Computer process data at a very fast speed. In fact, it can carry out millions of instructions per second. An ordinary Computer can count upto a million in one second. The speed of Computer is measured in terms of its capability to carry out number of instructions in a second. It is denoted by, Kilo Instructions Per Second (KIPS) and Million Instructions Per Second (MIPS). - **Accuracy:** The design of a Computer is such that it can't commit any mistake by itself. That is, if it is instructed properly, then there is absolutely no chance of any errors. Therefore the results given out by a Computer are 100% accurate and can be taken for granted.. - **Diligence:** Computer can perform repetitive jobs with constant attention and interest i.e., it does its job diligently without getting bored with the repetitive kind of jobs. - **Reliable:** Being a machine, it is capable of operating for long hours without any failure or fatigue. That means that no rest or tea/coffee breaks every now and then. - **Automatic Operations:** Once, necessary instructions and the required data is provided to it, Computer doesn't need any external help to complete its work. That way it is a machine that is capable of doing its job automatically. - **Versatility:** Computer is a versatile machine because of its capability to adapt to any situation. If it is provided with suitable software, it can do any type of work in any field effectively and efficiently. - **Large Storage Capacity:** The capacity of Computer to store data is practically limitless. It can store any volume of data and that too in such a way that it can retrieve any data item almost instantly. - **Intangible Benefits:** With the use of computer, the business can utilize the intangible benefits a Computer has with it. Like the flexibility, ability to accommodate growth, and the psychological factors which gives the business a competitive edge over the competitors. ## 10. Limitations/Disadvantages of Computer: Nothing in this world is perfect. Whatever advantages or facilities one has, there are some negatives or limitations about it also, and Computer is no exception. It has its own limitations. Following is the list of items, which can be considered as the limitations/disadvantages of Computer. - **Inflexibility:** The biggest disadvantage of computer is that it is not at all flexible in carrying out the instructions. They need exact commands and would obey them as it is. For example, if you are told to find the sum of two numbers, or add two numbers, or total the two numbers, you will carry out an addition operation on the two numbers. But if a computer is instructed to "add" two numbers and then you are supplying the numbers with the command to "sum" up these numbers, computer will not be able to do so. - **Requirement of Details:** Computer doesn't take any thing as "obvious" however simple or obvious something looks to you; it has to be given in details to the computer. For example if you want me to sip tea you will ask me to "sip it", but for computer you have to tell it "lift the cup from the table", and then "take it to the mouth", and then "sip it". - **Machine Dependency:** Since the computer does not store data/information in a direct-human-readable form, therefore you need computer to read stored data/information. In case of system breakdown or power failure your work would come to a standstill till the system is restored or some alternate arrangements are made. This way your entire work depends upon the proper functioning of computer. - **Specialist Users:** Because of technical requirements, not everybody can operate computers effectively. So you need specially trained personals to operate computer for the desired usage. This means an additional cost in terms of salary to hire such proficient personals. - **Loss of Data:** This is another area where the use of computer is feared most. Data is kept in electronic/magnetic form in computers. Both these forms are not permanent or secure. This data can easily get corrupted which, at times, is impossible to recover. - **Expensive:** The computer system and peripherals require a lot of investment because these are expensive equipments to buy and maintain. - **Security and Control:** Computers can be used for some malicious reasons by technically sound people to cause financial as well as other losses to you. In this way, you have to take additional security measures to protect your computer from such malicious users. ## 11. Use of RAM: RAM is used to store : - Operating System (Windows, DOS, UNIX, etc) as long as the computer is switched-on. - Application Software (Word, Excel, etc) while it is in use. - Input data i.e. the data required for processing during the processing. - Output data i.e. the information you get after the application software has processed the input data. - Temporary or Intermediate data i.e. the data which is required to complete the processing without the need of storing it permanently. ## 12. Use of ROM: ROM is basically used to permanently store: - Boot Strap Programs. Boot strap programs are the set of instruction which are required by the computer to make it operational when it is switched on. - Instructions to transfer the control to the operating system once it is loaded in the RAM of the switched-on computer. ## 13. Terms You Should Know: Every field, every subject has its own terminology. These terms have their specific meanings when used in that environment. Following is a list of such terms, which are used in Computer science environment. - **Data:** Data is the collection of facts and figures on which some processing is to be carried out. So the set of facts and figures, which are given to the computer for some processing, is called data. Data is the plural form of the Latin word "Datum", which means the "base". Since all the processing of computer is "based" upon it, therefore it is called data. Usually "Input" is called data. Following paragraph can be considered as an example of data. In the first term examination, Jafer Ahmed's Maths marks 25, Physics marks 35, Chemistry marks 20, and Computer marks 30. Masood Hasan's Maths marks 35, Physics marks 39, Chemistry marks 28, and Computer marks 39. Ali Ahmed's Maths marks 42, Physics marks 43, Chemistry marks 39, and Computer marks 40. - **Information:** The result of some processing, which is given out by computer is called information. The meaningful or the processed data is termed as information. Usually "output" is called information. Following paragraph can be considered as an example of information. | Name | Maths | Physics | Chemistry | Computer | Total | Percentage | |---|---|---|---|---|---|---| | Ali Ahmed | 42 | 43 | 39 | 40 | 164 | 82% | | Jafer Ahmed | 25 | 35 | 20 | 30 | 110 | 55% | | Masood Hasan | 35 | 39 | 28 | 39 | 141 | 71% | - **Instruction:** It is a command that is given to Computer to carry out a task. It is written in a form, which can be understood by a Computer. For example "Shut Down", "Open", "Close", "Save", "Save As". - **Program:** Program (or Computer program) is an ordered group of instructions, which are written in any of the computer language and given to the Computer to do one type of task completely. For example there can be a program, which can find and display the sum of two given numbers. - **Software:** Software is a concise set of Computer programs, which are combined and linked together for some defined needs. For example, Microsoft Word is software, which is designed to do word-processing. - **Hardware:** The machine components of computer are called hardware. Keyboard, keys, wires, and other components are the examples of hardware. - **Liveware:** The people involved in the study, design, improvements, and programming of Computer are known as liveware. - **Firmware:** ROM of a computer is called as firmware because it has software, which is "firmly" (permanently) held in it.