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Processor is mainly called as CPU Central Processing Unit and refers to as the mind of the computer. It is the main part of the computer because it is where all the calculations take place. It reads and executes every program instruction. It is very powerful and the most important component of the computer. It can deal with millions of instructions in per second, that is why most of the processor are dual or quad core processors. All the processors are made up of thin layers of transistors. Transistors are used to block the electricity when it is weak but will allow the electricity to pass through when it is strong enough. [1][2]

There are mainly two manufactures of computer microprocessors that are used in the computers. First is Intel and second is AMD.

Intel processors are made by Intel corporations. There are many types of Intel processor but currently second generation processors are used in all the computers and in most of the mobiles phones. Second generation processor are Intel Core i3, Core i5 and Core i7. Intel processor is widely used in most of the laptops by different companies such as Apple, Dell, Acer, and Samsung. An Intel processor consumes less power when they are running and executing the instructions; this is the biggest strength of the processor. It provides better quality of graphics and multimedia output. It does not get hot quickly, as it can stay cool for longer period of time.[3][4]

AMD (Advanced Micro Devices) processors are made by American multinational semiconductor company. AMD processor comes at second place after the Intel processor. AMD is considered as the only competitor for the Intel. AMD also has different types of processors but their latest processors are by the Phenom series and Fusion APU (Accelerated Processing Units) processors. The APU series processor is currently used in the computers and tends to give high-end graphical capabilities. AMD processor consumes more power than Intel and it is relatively cheaper than Intel processors.[3][4]

Main elements of processor:

CPU (Central processing unit) consists of three main elements and all the elements works together. The three basic elements are Registers, The ALU (Arithmetic Logic Unit) and the CU (Control Unit).

Registers: Registers are also known as temporary storage for the CPU and can be accessed very fast. CPU uses the registers to store the information temporarily. It helps in speeding up the computer because it can store the data temporarily, when the data is sent from RAM to processor for execution and coming back after the processing is done. Registers are located within the processor. [5][6]

ALU: It does all the calculations of the CPU. It can perform basic calculations such as addition, subtraction, multiplication and division. It can also carry out comparison of figures like comparing numbers or letters and then based on the result of the comparison it takes action. The possible result could be less than, greater than or equal to. [5]

Control Unit: Control Unit can also be called as the brain of the CPU because it controls the flow of the information and all the functions through the processor. Control unit does not execute instructions by self; instead it tells other parts of the system to execute it. In order to perform the functions, it must communicate with both arithmetic logic unit and memory. It instructs the ALU on which arithmetic and logical operation is to be performed. [5][6]

Functions of processor:

The main function of this processor is to process the instructions of the program. These instructions tells the computer that what to do. These instructions could be logic operations or calculations. Processor has four main primary functions and they are fetch, decode, execute and store. This process often called as Fetch-execute cycle. [Figure 1] Fetch-execute cycle means it reads each instruction into the CPU from program memory, then it translate into computer language and it performed. [7][8]

Fetch: This is where al l the instructions are read from the memory because each instruction is stored in the memory and has its own address. These addresses allow the CPU to takes the instructions from the Program Counter (PC). Program Counter tells the CPU that what instruction CPU should execute next. [7][9][10]

Decode: Decode is when the instructions are converted into the computer language. The compute language is called binary, which is easily understandable by the CPU. In decode, you have CU (Control Unit). Control Unit helps to decode the instructions and it also helps to execute the instructions by generating all the required signals. [7][9]

Execute: In the execute process one of the three options is executed, based on the instructions. First option is that, it can perform some calculations and ALU is used to execute the calculations. Second, it can store or move the information to memory or one memory to another. Third, if it is required it can jump to different address. [7][10]

Store: This is when the CPU stores the information in the memory after executing the instructions. [7]


Memory is a very vital part of the computer. Memory is used to store the data and the data could be stored as permanent or temporary storage. There are two main types of memory and that is primary and secondary memory [Figure 2]. Both the memories are different from each other, when it comes to their capacity, speed and cost. Computer can have various types of memories that can be installed. It could be either internal or external memory. You can easily access the stored information from the memory. [11][12]

Primary memory: Primary memory is also known as Main memory of the computer. It holds the instructions and data that can be directly retrieved by the CPU. Primary memory is a Volatile-memory, which means it loses the data when the system is turned off. CPU use the address and the memory buses to access the data from the primary memory.[12][13]

The different types of primary memory are:

RAM (Random Access Memory):- RAM is used as a primary storage in the computer system. This is where the data, applications and operating system is stored temporarily when they are currently in used by the user. These programs are directly accessed by the processor. The RAM loss all its data when the system is turned off. It is a Volatile memory. [12][14]

ROM (Read-Only Memory): ROM acts as a type of permanent memory. The data that is stored in the ROM cannot be changed. It can only be read but cannot be used as to write new data. The main advantage of ROM is that the program is always available in the main memory and it does not need any secondary storage device to load the data. It is used for certain functions in the system, mainly for two different reasons. The first is Permanence (data is always there whether the system is on or off) and the second is security (as it cannot be easily modified). It is a Non-Volatile memory. [15][16]

Cache: Cache is a high speed memory and is available inside the CPU. It helps the CPU to access the data quickly and the information is stored in the RAM memory. It also helps to run the platform faster. The advantage of Cache memory is that the more you use this memory, the more you can store additional information.[17][18]

Registers: Registers is the small memory that is available in the CPU. It is one of the fastest memories in the CPU because it speeds up the operations of the CPU. It allows the CPU to quickly access the data or instructions that is currently stored in the registers. It is refers to as temporarily memory because the data stays in the memory until the system is on or it is currently in use by the system. [19][20]

The different types of registers are:

PC (Program Counter)- It fetches the next instruction by using its address , IR (Instruction register) â€" It holds the last fetched instruction, MAR (Memory address register)- In memory, it got the address of a location, and MBR (Memory buffer register)-It stores the data that is going or coming from the memory. [21]

Secondary Memory: Secondary Memory is used as permanent storage for the data. It can hold large amount of data in it and it does not get deleted. This means, if the system is turned off it does not lose the data from the memory. Secondary memory is not directly accessed by the CPU; instead the data is firstly loaded in the main memory before accessing. Secondary memory often called as Non-volatile storage. [11][22]

The different types of secondary memory are:

Hard drive: Hard drive is mainly integrated inside all the computer case and in all the laptops. It is the man part of the computer because it stores all the important data of the computer such as programs, images, videos etc. External hard drives can also be used to store the information. The information can be retrieved faster from the hard disk. [23][24]

Optical devices (CD/DVD’s): CD or DVD drives are mainly used in all the computer systems. It is used to store the information and it can hold large amount of data. CD or DVD acts as a read only memory because you can only read the information from it unless it is writeable. This means on writeable CD or DVD, it allows to write the file on it. CD drives are used to read and write the information from the CD. It used laser to get the data from the CD or DVD. [23][24]

Flash drives: Flash drives also known as USB (Universal serial bus). It is a portable device and can be plugged into any computer. It is also used to store the files such as images, program setups, songs etc. These files can easily be moved from one place to another. Flash drives can easily be carried to any place. They are compact is design and available in different storage sizes from 64MB to 64GB. [24][25]

Input and output element

Input and Output elements are very important part of the system. Without these elements the system will not be able to work and will not produce any data. These devices communicate with each other on user’s input and gives out the result in different formats such as on screen or as a hard copy. Output results can be used to tell other machines that what to do or what not to do for different operations. [26]

To/From the user:

The different types of Input elements are:

Keyboard: Keyboard is the main part of the computer as it is use to input the information into the system. It automatically converts the input key into computer code, when user presses any key from the keyboard. Each character is used by different computer code by the computer. All computers use the same binary code called ASCII (American Standard Code for Information technology. Keyboard can be wired or wireless. [27][28]

Mouse: It is an input device and used as a pointing device on the computer screen. The user can use the mouse on flat surface. It has mainly two buttons on it and a roller in the middle of the buttons. Buttons allow the user to select, erase, or draw on the screen. Mouse only works when user click the button. In modern mouse they use laser instead of ball to detect the signal. [27]

Scanner: Scanners are used to scan the hard copy documents into the system as an electronic file. Each scanner has different specifications like different image resolution, different speed. The different types of scanners are Flatbed, Sheet-fed and Drum scanners. These three printers have different specifications from each other. [29]

Joystick: Joystick is mainly used for playing games on the computer. Most of the joysticks have two buttons and it is called as triggers. Joystick only works when user does any physical movement and which then show the result on the screen. [28][30]


To/From the network:

The different types of Output elements are:

NIC (Network Interface Card):

Graphics Card:


Support Elements






Power supply:



Pic for fetch cycle, input output stuff and memory pic