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UNIT – 1
Components of Computer : Processor, Memory, input – output unit, difference between organization and architecture, hardware software interaction, Number system : concept of bit and byte, types and conversion, Complement's : 1's complement, 2's complement, Binary arithmetic : Addition, Overflow, Subtraction. Computer: A computer is a combination of hardware and software resources which integrate together and provides various functionalities to the user. Hardware are the physical components of a computer like the processor, memory devices, monitor, keyboard etc. while software is the set of programs or instructions that are required by the hardware resources to function properly. There are a few basic components that aids the working-cycle of a computer i.e. the Input- Process- Output Cycle and these are called as the functional components of a computer. It needs certain input, processes that input and produces the desired output. The input unit takes the input, the central processing unit does the processing of data and the output unit produces the output. The memory unit holds the data and instructions during the processing. Digital Computer: A digital computer can be defined as a programmable machine which reads the binary data passed as instructions, processes this binary data, and displays a calculated digital output. Therefore, Digital computers are those that work on the digital data. Details of Functional Components of a Digital Computer
A processor or processing unit is a digital circuit which performs operations on some external data source, usually memory or some other data stream. Processor is popualrly referred to as the " BRAIN" of the computer , is responsible for processing the data inside the computer system. It is also responsible for controlling all other components of the system. The main operations of CPU include four phases –
- Fetching instructions from the memory.
- Decoding the instructions to decide what operations to be performed.
- Executing the instructions.
- Storing the results back in the memory. This four phase process is known as the CPU cycle. Parts Of Processor : Input Unit : The input unit consists of input devices that are attached to the computer. These devices take input and convert it into binary language that the computer understands. Some of the common input devices are keyboard, mouse, joystick, scanner etc. Central Processing Unit (CPU) : Once the information is entered into the computer by the input device, the processor processes it. The CPU is called the brain of the computer because it is the control center of the computer. It first fetches instructions from memory and then interprets them so as to know what is to be done. If required, data is fetched from memory or input device. Thereafter CPU executes or performs the required computation and then either stores the output or displays on the output device. The CPU has three main components which are responsible for different functions – Arithmetic Logic Unit (ALU), Control Unit (CU) and Memory registers
Primary Memory Primary Memory is a type of Computer Memory which is directly accessed by the Preprocessor. It is basically used to store data on which computer is currently working. It has lesser storage than Secondary Memory. It is basically of two types:
- Random Access Memory (RAM)
- Read Only Memory (ROM) Types of Primary Memory Random Access Memory (RAM) is a type of computer memory that is used to temporarily store data that the computer is currently using or processing. RAM is volatile memory, which means that the data stored in it is lost when the power is turned off. RAM is typically used to store the operating system, application programs, and data that the computer is currently using. It is also called read-write memory or the main memory or the primary memory. The programs and data that the CPU requires during the execution of a program are stored in this memory. It is a volatile memory as the data is lost when the power is turned off.
Types of Random Access Memory (RAM) Static RAM (SRAM) Dynamic RAM (DRAM)
1. Static RAM: SRAM stands for Static Random Access Memory. It is a type of semiconductor which is widely used in computing devices and microprocessors. 2. Dynamic RAM: DRAM stands for Dynamic Random Access Memory. It is made of Capacitors and has smaller data life span than Static RAM. Advantages of Random Access Memory (RAM) Speed: RAM is much faster than other types of storage, such as a hard drive or solid-state drive, which means that the computer can access the data stored in RAM more quickly. Flexibility: RAM is volatile memory, which means that the data stored in it can be easily modified or deleted. This makes it ideal for storing data that the computer is currently using or processing. Capacity: The capacity of RAM can be easily upgraded, which allows the computer to store more data in memory and thus improve performance. Power Management: RAM consumes less power compared to hard drives, and solid-state drives, which makes it an ideal memory for portable devices.
Types of Read-Only Memory (ROM)
- PROM (Programmable Read-Only Memory)
- EPROM (Erasable Programmable Read Only Memory)
- EEPROM (Electrically Erasable Programmable Read Only Memory)
- MROM (Mask Read Only Memory) 1. PROM (Programmable read-only memory): It can be programmed by the user. Once programmed, the data and instructions in it cannot be changed. 2. EPROM (Erasable Programmable read-only memory): It can be reprogrammed. To erase data from it, expose it to ultraviolet light. To reprogram it, erase all the previous data. 3. EEPROM (Electrically erasable programmable read-only memory): The data can be erased by applying an electric field, with no need for ultraviolet light. We can erase only portions of the chip. 4. MROM(Mask ROM): Mask ROM is a kind of read-only memory, that is masked off at the time of production. Like other types of ROM, mask ROM cannot enable the user to change the data stored in it. If it can, the process would be difficult or slow. Advantages of Read Only Memory (ROM) Non-volatility: ROM is non-volatile memory, which means that the data stored in it is retained even when the power is turned off. This makes it ideal for storing data that does not need to be modified, such as the BIOS or firmware for other hardware devices. Reliability: Because the data stored in ROM is not easily modified, it is less prone to corruption or errors than other types of memory. Power Management: ROM consumes less power compared to other types of memory, which makes it an ideal memory for portable devices. Disadvantages of Read Only Memory (ROM) Limited Flexibility: ROM is read-only memory, which means that the data stored in it cannot be modified. This can be a problem for applications or firmware that need to be updated or modified. Limited Capacity: The capacity of ROM is typically limited, and upgrading it can be difficult or expensive. Cost: ROM can be relatively expensive compared to other types of memory, such as hard drives or solid-state drives, which can make upgrading the memory of a computer or device more costly.
Difference between RAM and ROM Difference Random Access Memory (RAM) Read Only Memory (ROM) Data-Retention RAM is a volatile memory that could store the data as long as the power is supplied. ROM is a non-volatile memory that the could retain the data even when the power is turned off. Read/Write Read and write operations are supported. Only read operations are supported. Use Used to store the data that has to be currently processed by CPU temporarily. It is typically used to store firmware or microcode, which is used to initialize and control hardware components of the computer. Speed It is a high-speed memory. It is much slower than the RAM. CPU Interaction CPU can easily access data stored in RAM. CPU cannot easily access data stored in ROM. Size and Capacity Large size with higher capacity, concerning ROM. Small size with less capacity, concerning RAM. Used as/in CPU Cache, Primary memory. Firmware, Micro-controllers. Accessibility The data stored is easily accessible. The data stored is not as easily accessible as in the concerning RAM. Cost RAM is more costlier than ROM. ROM is cheaper than RAM. Chip Size A RAM chip can store only a few gigabytes (GB) of data. A ROM chip can store multiple megabytes (MB) of data. Function Used for the temporary storage of data currently being processed by the CPU. Used to store firmware, BIOS, and other data that needs to be retained.
Output Devices Output Devices are the devices that show us the result after giving the input to a computer system. Output can be of many different forms like image, graphic audio, video, etc. Display Monitors CRT monitor LCD monitor TFT monitor LED monitor Printers Impact Printers Dot matrix Diasy Wheel Drum Printers Non impact printers Ink jet printers Laser printers Special purpose printers Plotters Drum Plotter Flat bed Plotter Ink jet Plotter Electrostatic Plotter Voice output systems Projectors In computing, input/ output or I/O is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals or data received by the system and the outputs are the signals or data sent from it. The term can also be used as part of an action to " perform I/O" is to perform an input or output operation. I/O devices are the pieces of hardware used by a human( or other system) to communicate with a computer. For instance, a keyboard or computer mouse is an input device for a computer, while monitors and printers are output devices. Devices for communication between computers, such as modem and network cards, typically perform both input and output operations. The designation of a device as either input or output depends on perspective. Mouse and keyboards take physical movements that the human user outputs and convert them into input signals that a computer can understand; the output from these devices is the computer's input. Similarly printers and monitors take signals that a computer outputs as input, and they convert these signals into a representation that human user can understand. From the human user's perspective the process of reading or being these representation is receiving output, this type of interaction between computers and human is studied in the field dof human computer interaction. In computer architecture, the combination of the CPU and main memory, to which the CPU can read or write directly using individual instructions is considered the brain of a computer. Any transfer of information to or from the CPU/ memory combo, for example by reading data from a disk drive, is considered I/O. The CPU and its supporting circuitry may provide memory-mapped I/O that is used in low – level computer programming, such as in the implementation of device drivers or may provide
access to I/O channels. An I/O algorithm is one designed to explicit locatlity and perform efficiently when exchanging data with a secondary storage device, such as disk drive.
Difference between Organisation and Architecture :
What is Computer Architecture? Computer Architecture is a blueprint for design and implementation of a computer system. It refers to the overall design of a computer system, including the hardware and software components that make up the system and how they interact with each other. Computer architecture provides the functional details and behavior of a computer system. It involves the design of the instruction set, the microarchitecture, and the memory hierarchy, as well as the design of the hardware and software components that make up the system. Computer Architecture mainly deals with the functional behavior of a computer system and covers the "What to do?" part. It gives the functional description of requirements, design, and implementation of the different parts of a computer system. In the designing process of a computer system, the computer architecture is to be defined before the computer organization. What is Computer Organization? Computer Organization refers to the way in which the hardware components of a computer system are arranged and interconnected. It implements the provided computer architecture and covers the "How to do?" part. Computer Organization is to be defined after the decision of the computer architecture. It just provides information that how operational attributes of a computer system are linked together and help in realizing the architectural specification of the computer. It involves the design of the interconnections between the various hardware components, as well as the design of the memory and I/O systems. Differences between Computer Architecture and Computer Organization The following table highlights how Computer Architecture is different from Computer Organization – Key Computer Architecture Computer Organization Purpose Computer architecture explains what a computer should do. Computer organization explains how a computer works. Target Computer architecture provides functional behavior of computer system. Computer organization provides structural relationships between parts of computer system. Design Computer architecture deals with high level design. Computer organization deals with low level design. Role Computer architecture assists in understanding the functionality of the computer. Computer organization helps to understand the exact arrangement of component of a computer.
switch is open the bulb isn't supplied with the required voltage and hence it doesn't work. This is how voltage levels control the LED bulb. The physical act of turning ON and OFF by opening and closing the LED bulb can be substituted by any other mechanism. This works fine until this mechanism actually is able to operate as per your requirement. In case of computers, the entire hardware is supplied varying voltages due to which different components get activated at the same or different time instances and achieve a particular task. Finally all the binary data in a computer is nothing but the voltage level information, for which a particular task is assigned to be executed. The entire sequence of events that occur for hardware and software interaction is under the control of Operating system. All the driver software help the Operating system to actually communicate with the hardware, so as to execute the application software.
Number system :
The technique to represent and work with numbers is called number system. The number system is a representation for a given number. BIT : A bit is a binary digit, the smallest increment of data on a computer. A bit can hold only one of two values: 0 or 1, corresponding to the electrical values of OFF or ON, respectively. Because bits are so small, we rarely work with information one bit at a time. Bits are usually assembled into a group of eight to form a byte. The number system are of two types – 1)Non – positional number system 2)Positional number system. Non – Positional number system – Non-positional number system is also known as non-weighted number system. Digit value is independent of its position. Non-positional number system is used for shift position encodes and error detecting purpose. Few examples of non-weighted number system are gray code, roman code, excess-3 code, etc. Positional number system – In positional number system, each symbol represents different, value depending on the position they occupy in a number. In positional number system, each system has a value that relates to the number directly next to it. The total value of a positional number is the total of the resultant value of all position. e.g. 12 can be 110 + 21 = 10 + 2 = 12 Types of positional number system – Based on the base value and the number of allowed digits, number systems are of many types. The four common types of Number System are: Binary Number System Octal Number System
Decimal Number System Hexadecimal Number System Binary Number System : The binary number system uses only two digits: 0 and 1. The numbers in this system have a base of 2. Digits 0 and 1 are called bits and 8 bits together make a byte. The data in computers is stored in terms of bits and bytes. The binary number system does not deal with other numbers such as 2,3,4,5 and so on. For example: 10001 2 , 111101 2 , 1010101 2 are some examples of numbers in the binary number system. Octal Number System The octal number system uses eight digits: 0,1,2,3,4,5,6 and 7 with the base of 8. The advantage of this system is that it has lesser digits when compared to several other systems, hence, there would be fewer computational errors. Digits like 8 and 9 are not included in the octal number system. Just like the binary, the octal number system is used in minicomputers but with digits from 0 to 7. For example, 35 8 , 238 , and 141 8 are some examples of numbers in the octal number system.
Conversion of Number Systems A number can be converted from one number system to another number system using number system formulas. Like binary numbers can be converted to octal numbers and vice versa, octal numbers can be converted to decimal numbers and vice versa, and so on. Let us see the steps required in converting number systems. Steps for Conversion of Binary to Decimal Number System To convert a number from the binary to the decimal system, we use the following steps. Step 1: Multiply each digit of the given number, starting from the rightmost digit, with the exponents of the base. Step 2: The exponents should start with 0 and increase by 1 every time we move from right to left. Step 3: Simplify each of the above products and add them. Let us understand the steps with the help of the following example in which we need to convert a number from binary to decimal number system. Example: Convert (100111) 2 into the decimal system. Solution: Step 1: Identify the base of the given number. Here, the base of 100111 2 is 2. Step 2: Multiply each digit of the given number, starting from the rightmost digit, with the exponents of the base. The exponents should start with 0 and increase by 1 every time as we move from right to left. Since the base is 2 here, we multiply the digits of the given number by 2^0 , 2^1 , 2^2 , and so on from right to left. 1 0 0 1 1 1 1 * 2^0 1 * 2^1 1 * 2^2 0 * 2^3 0 * 2^4 1 * 2^5 Step 3: We just simplify each of the above products and add them. 1 0 0 1 1 1 1 * 2^0 = 1 * 1 = 1 1 * 2^1 = 1 * 2 = 2 1 * 2^2 = 1 * 4 = 4 0 * 2^3 = 0 * 8 = 0 0 * 2^4 = 0 * 16 = 0 1 * 2^5 = 1 * 32 = 32
SUM 39 Here, the sum is the equivalent number in the decimal number system of the given number. Or, we can use the following steps to make this process simplified.
100111 = (1 × 2^5 ) + (0 × 2^4 ) + (0 × 2^3 ) + (1 × 2^2 ) + (1 × 2^1 ) + (1 × 2^0 )
= (1 × 32) + (0 × 16) + (0 × 8) + (1 × 4) + (1 × 2) + (1 × 1)
Thus, (100111) 2 = (39) 10. Example: Convert (110000100) 2 into the octal system. Solution: Step 1: We convert binary to octal by grouping 3 bits from the right most side. 1 1 0 0 0 0 1 0 0 = 6 0 4 Step 2 : Now we combine all the read parts in octal number Thus, (110000100) 2 = (604) 8. Example: Convert (110000100) 2 into the hexadecimal system. Solution: 1st^ way Step 1: We convert binary to hexadecimal by grouping 4 bits from the right most side. 1 1 0 0 0 0 1 0 0 = 1 8 4 Step 2 : Now we combine all the read parts in hexadecimal number. Thus, (110000100) 2 = (184) 16. Example: Convert 1010111100 2 to the hexadecimal system. Solution: 2nd^ way Step 1: Convert this number to the decimal number system as explained in the above process. 1 0 1 0 1 1 1 1 0 0 0 * 2^0 = 0 * 1 = 0 0 * 2^1 = 0 * 2 = 0 1 * 2^2 = 1 * 4 = 4 1 * 2^3 = 1 * 8 = 8 1 * 2^4 = 1 * 16 = 16 1 * 2^5 = 1 * 32 = 32 0 * 2^6 = 0 * 64 = 0 1 * 2^7 = 1 * 128= 0 * 2^8 = 0 * 256= 0 1 * 2^9 = 1 * 512= 512
SUM - 700 Thus, (1010111100) 2 = (700) 10 Step 2: Convert the above number (which is in the decimal system), into the required number system (hexadecimal).
Solution: Step 1: Identify the base of the required number. Since we have to convert the given number into the octal system, the base of the required number is 8. Step 2: Divide the given number by the base of the required number and note down the quotient and the remainder in the quotient-remainder form. Repeat this process (dividing the quotient again by the base) until we get the quotient less than the base. 8 4320 8 540 0 8 67 4 8 8 3 1 0 Step 3: The given number in the octal number system is obtained just by reading all the remainders and the last quotient from bottom to top. Therefore, (4320) 10 = (10340) 8 Example: Convert (4285) 10 into the hexadecimal system. Solution: Step 1: Identify the base of the required number. Since we have to convert the given number into the hexadecimal system, the base of the required number is 16. Step 2: Divide the given number by the base of the required number and note down the quotient and the remainder in the quotient-remainder form. Repeat this process (dividing the quotient again by the base) until we get the quotient less than the base. (which is D in hexadecimal) (which is B in hexadecimal) Step 3: The given number in the hexadecimal number system is obtained just by reading all the remainders and the last quotient from bottom to top. Therefore, (4285) 10 = (10BD) 16 Example: Convert (144) 8 into the decimal system. Solution: The base of 144 8 is 8. We will convert this number into the decimal system as follows: 1 4 4 4 * 8^0 = 4 * 1 = 4 4 * 8^1 = 4 * 8 = 32 4 * 8^2 = 4 * 64 = 64
SUM = 100 Thus, (144) 8 = (100) 10
Example : Convert (5BC) 16 into the decimal system. Solution: 5BC 16 is in the hexadecimal system. We know that B = 11 and C = 12 in the hexadecimal system. So we get the equivalent number in the decimal system using the following process: 5 B C = 5 11 12 12 * 16^0 = 12 * 1 = 12 11 * 16^1 = 12 * 16 = 176 5 * 16^2 = 12 * 256 = 1280
SUM - 1468 Thus, (5BC) 16 = (1468) 10 Conversion of floating numbers into binary : Example : 4. Where 4 is an integral part and 0.25 is a fractional part. Step 1 : Integral part (4)
- To convert an integral part into binary, just follow the usual method. 2 4 2 2 0 1 0 Step 2 : Fractional part (0.25)
- to convert the fractional part to binary, multiply fractional part with 2 and take the one bit which appears before the decimal point.
- Follow the same procedure with after the decimal point (.) part until it becomes 1. So, 0.25 * 2 = 0.50 // take 0 and move .50 to next 0.50 * 2 = 1.00 // take 1 and stop the process Therefore 0.25 = (01) 2 Step 3 : Combine both integral and fractional part (4.25) 10 = (100.01) 2 Example : 10. Integral part 10 = (1010) 2 Fractional part (0.75) 0.75 * 2 = 1.50 // take 1 and move .50 to next step. 0.50 * 2 = 1.00 // take 1 and stop the process as there is no remainder. Ans = (10.75) 10 = (1010.11) 2 Note : Some fractional part numbers will not end up with 1.0 with the above method. In floating storage, the computer will allocate 23 bits for the fractional part. So its enough to do the above method at max 23 times.
