A computer is an electronic device capable of manipulating amount and symbols, first taking input, processing it, saving and offering result under a control of set in place instructions which is actually a program. A general goal computer requires the following hardware components: memory space, storage space device (hard drive), input device (keyboard, mouse etc. ), productivity device (screen, computer printer etc. ) and central control unit (CPU). Many other components are involved in addition to the outlined components to interact efficiently.

Computers can be classified by size and electricity the following:

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Personal computer: Personal computers are small computer systems predicated on a microprocessor. A personal computer has a keyboard for inputting data, a monitor for output and a storage space device for saving data.

Workstation: workstations are usually powerful than a personal computer. It includes more powerful microprocessor and a higher-quality screen.

Minicomputer: Mini pcs are multi-user computer capable of aiding from 10 to a huge selection of users concurrently.

Mainframe computer: Mainframe personal computers are powerful multi-user computer with the capacity of supporting many hundreds or thousands of users together.

Super computer: Super computers are extremely fast computers that is capable of doing vast sums of instructions per second.



A computer system can be symbolized using the next block diagram:




Timing and


Address Bus






Mouse etc.

Data Bus

Control Bus


The CPU is can be broadened into three main parts: The ALU (Arithmetic and Reasoning Unit), The Bus software Unit, as well as the Control Bus. The clock is an electronic circuit that gives regular pulses to the CPU. Faster clock speeds means more pulses to the CPU and the instructions are stepped through faster. The recollection chip contains an incredible number of separate ram stores and each one of these locations has a distinctive number. That is known as memory address. The CPU stores data at these addresses and fetch the content back when required.

RAM means Random Access Recollection. These potato chips store the instructions for running the operating system and any computer application. This ram also stores all the info that is being worked on. RAM is a volatile storage area meaning it only stores data while the computer remains switched on. When powered down, it loses all the stored data. ROM (Read Only Storage area) on the other side is a chip with program instructions forever burned into it. This content is not lost even if the device is powered down.

The CPU can either fetch data from or write data when the correct recollection location is reached. Such data is transferred from the CPU to the memory space location along the info Bus. The control Bus is a couple of monitors on the computer’s motherboard that run from the CPU to the devices and works under the way of the CPU.


Logic gates perform logical operation using one or more logic inputs and produce a single logic outcome. It processes alerts which stand for true or bogus. It is called Boolean reasoning and is most commonly used in digital circuits. Reasoning gates are discovered by their function: NOT, AND, NAND, OR, NOR, EX-OR and EX-NOR and they’re usually symbolized by capital letters.

Logic Gate Symbols

There are two group of symbols for logic gates: the original symbols that have distinctive patterns making them easy to discover so they are really widely used, and the International Electro complex Commission (IEC) icons that are rectangles with symbolic inside to show the gate function.

Traditional Symbols

Source: http://www. kpsec. freeuk. com/gates. htm


Source: http://www. kpsec. freeuk. com/gates. htm

Inputs and Outputs

All Gates except a NOT gate have several inputs. A NOT gate has only one input and all gates have only 1 output. In the next physique, A and B are inputs and Q is the result.

Source: http://www. kpsec. freeuk. com/gates. htm

Other types of gate used are NOT gate, AND gate, NAND (NOT AND) gate, OR gate and NOR (NOT OR) gate.

Truth tables

A truth desk is an excellent way to show the function of a logic gate. It shows the productivity states for each and every possible blend of input claims. The icons 0 (incorrect) and 1 (true) are usually found in truth tables. The example truth table on the right shows the inputs and output of the AND gate.

Input A

Input B

Output Q













Computer numbering system

Humans speak to each other in a specific language and we use different words and words. Although we type words and letters in the computer, the computer translates those words and characters into numbers. Computers discuss and understand in statistics. Those amount systems are: Decimal, Hexadecimal, and Binary.

The Decimal Number System is the system is most regularly found in arithmetic and in everyday living. The decimal amount system is also called the base 10 quantity system as the positioning in the number presents an incremental amount with a base of 10. Each position only is made up of a number between 0 and 9.

The Hexadecimal amount system can be used to represent storage addresses or shades. It is also known as the base 16 quantity system, because each position in the quantity represents an incremental number with a base of 16. Because the amount system is displayed in 16s, there are just 10 numbers and 5 letters (A to F).

The Binary number system is utilized by most machines and electronic devices to talk. Additionally it is known as the bottom 2 amount system, because each position in the number signifies an incremental number with a base of 2. Because it is represented it 2s, there are only 2 numbers that can be a value in each position 0 or 1.


The CPU is the intellect of the device but it requires a pre-written program to build, use and modify the data. If the computer must compare two amounts, or add two amounts, this is completed inside the CPU and the numbers have to be fetched into the CPU from the computer’s memory space chip. The three main components of CPU are: Arithmetic reasoning Unit (ALU), Bus Software product, and the Control Bus.

Arithmetic Logic Unit (ALU) holds out all the computations and decision making responsibilities. The ALU uses devices called gates that get a number of inputs and established up what function they are designed to perform, outputs a result. The basic businesses of any ALU include adding and subtracting binary ideals as well as executing logical operations such as AND, NOT, OR AND XOR.

The Bus Software Unit takes the data to and from the CPU which is kept inside inner registers (small memory space stores) across the exterior Data Bus to read and write recollection and devices. THE INFO Bus bears information in both directions. The Bus Interface Unit also places the mandatory location addresses on the Address Bus, so the required devices can be seen for reading or writing.

The Control Bus is the physical interconnection that bears control information between the CPU and other devices within the computer. It decodes all program instructions and dictates all the CPU’s control and timing mechanisms. It sends out the read and write indicators on the Control Bus.


The computer has to temporarily store this program and data in an area where it could be utilized by the computer’s processor chip to work. This area is known as the computer’s memory. It consists of computer potato chips that can handle stocking information. These information could be: the operating system (e. g. DOS, windows etc. ), the instructions of this program to perform (e. g. a databases or a drawing program), or the data that is utilized or created (e. g. letters from word-processing or information from a database). There are different types of storage area used in a pc system. They may be: Cache memory space, Random Access Storage (RAM), Read Only Recollection (ROM), and Virtual Storage.

Cache memory is extremely fast recollection that is made into a computer’s CPU (L1 cache) or sometimes located next to it on another chip (L2 cache). L1 cache is faster than L2 cache as it is made in to the CPU. Nowadays, newer computer come with L3 cache which is faster than Ram memory but slower than L1 and l2 cache. Cache recollection can be used to store instructions that are repeatedly required to run programs and really helps to improve overall system quickness. The reason why it is so fast would be that the CPU doesn’t have to make use of the motherboard’s system bus for data copy.

Random Access Memory (RAM) is the memory chip that includes a large volume of cells, each cell having a fixed capacity for stocking data and unique address. Ram memory is a volatile storage which means all the programs and data in the ram is lost when the machined is powered down. There are different types of Ram memory modules available such as SODIMM, SDRAM, DDR, DDR2 and DDR3. SODIMM are being used for notebooks whereas the others are used for desktop pcs.

Read Only Memory (ROM) is a memory space chip where the program instructions are permanently burned into. It is non-volatile this means its content is not lost even though the machined is switched off. It is utilized to store some of the system programs that keep the computer running smoothly. For instance computer BIOS (basic type out system) is stored on the ROM. There will vary types of ROM available such as Programmable ROM (PROM), Erasable Programmable ROM (EPROM), and Electrically Erasable Programmable ROM (EEPROM).

Virtual Memory is an integral part of most operating-system. It is employed when the quantity of RAM is not enough to perform all the programs. When the operating system, a contact program, a web browser, a word cpu, a Photoshop program are loaded in to the RAM simultaneously, the RAM will never be able to deal with all applications and so the computer talks about Ram memory for areas which may have not been used recently and copies them onto the hard drive. This frees up space in RAM to fill new application. But because the read/write rate of a difficult drive is a lot slower than that of RAM, the performance is not acceptable. It is not recommended to use virtual memory as it is gradual. The solution to this problem is always to upgrade the storage.


A computer system is not complete without system software. To get a computer to execute any responsibilities, both software and hardware are similarly important. System software offers life to hardware. System softwares are the documents and programs that make up a computer’s operating-system. It offers libraries of functions, system services, driver for hardwares, system personal preferences, and other settings files. System software comprises of Assembler, Debugger, Compilers, Operating System, File management tools etc. The machine software is installed using the pc when the operating system is installed. It can even be updated by jogging programs such as “windows update”.

The system software is also called “low-level” software as it operates at the most basic degree of the computer. It generates the user software and allows the operating-system to connect to the hardware; however system software is not designed to be run by the end user like application programs. Request programs such as browser, or Microsoft word is often employed by the end customer whereas the end user does not use an assembler program unless he/she is some type of computer programmer. The system software runs in the background and thus an individual does not have to worry about what the machine software is doing.


In the article, the basic composition of any computer system was identified with diagram. Different components such as CPU, recollection, BUS, suggestions/output devices that form your computer system were determined and explained. General ideas about Logic gates were given and different number systems used by computers to stand for data were also defined. As the CPU is the main part of your computer system, it was further looked into and Arithmetic Logic Device, Control Bus and Bus software Unit were mentioned. Different types of ram and their uses were explained and the importance of the machine software was talked about finally.