Primary Memory

Primary memory:

                It is also called main memory or internal memory. It is more expensive than secondary memory. The primary memory of the computer are Read Only Memory and CACHE MEMORY .

RAM: RAM is a volatile memory It is also known as the temporary memory. It is volatile memory because information inside the RAM is erased when the power supply is switched off. It is the working memory of the computer system. It is also called Read Write Memory because data can be written and read from it. All the programs and data must be loaded into Ram before they are executed or processed.The two types of RAM are Static Ram and Dynamic Ram.

SRAM: It is static RAM . It is made up of transistors so doesn’t need periodic refresh to preserve the information.  It is much faster than DRAM.

It need s a periodic refresh to preserve the information. Synchronous Dynamic RAM is a kind of DRAM.

By increasing the amount of RAM , the performance of computer of computer increases because more programs and data can be loaded in it at a time. But we should be clear that only memory is not the deciding factor for the performance of the computer.

Secondary Memory

Secondary memory:

                The secondary memory is the permanent memory where information are stored for future use. The stored information can be system instruction , programs, user documents etc. Secondary memory is also called mass storage. It is very inexpensive as compares to primary memory . But it is slower than primary memory. Secondary memory are: Hard disk, floppy disk, Magnetic tape,  Zip disk, Super disk, Flash disk, CD, DVD etc.

On the basis of storage temporary secondary memory  mediums are categorized into two types.

                1. Magnetic Storage Media

                2. Optical Storage Media

                Magnetic Storage Media:

                                It uses magnetically sensitive material such as iron oxide to store data on it. The most common magnetic storage media are hard disk, floppy disk, tape disk and zip disk. The read/write head of the magnetic storage device consists of an electromagnet which reads data from and write data to the magnetic storage media.

Some magnetic storage media are Magnetic Tapes, Floppy disk, Zip disk, Super disk, Hard disk.

Optical Storage media:

        They provide a huge storage capacity. Optical storage device uses light technology to read data from and write data to the optical medium. In optical disks, data are stored in the form of lands and pit. Land is a surface which reflects light, representing data bit 1 but pit is a rough surface which scatters light, repepresenting data bit 1 but pit is a rough surface which scatters light, representing data bit 0.
The most popular optical disks are CD-ROM, CD-RW and DVD-ROM

ROM

ROM:

ROM is a permanent  memory it is also known as a volatile memory  because ROM retain the information  in  it even the computer is switched off ROM stores the computer configuration information which the computer needs all the time. We can not  write anything inside ROM so, it is called Read Only Memory.

There are three types of ROM

PROM

EPROM

EEPROM

PROM stands for the programmable Read Only Memory . It can be modified only once. PROM allows to write microcode programs using a special device called PROM.

EPROM  stands for Erasable Programmable Read Only Memory. It can be erased and programmed  multiple times.

EEPROM: EEPROM stands for electrically Earasable Programmable Read Only Memory. It can be erased  and programmed repeatedly with the help of electrical pulses.

Hardware

Computer hardware

Computer hardware are the physical components which can see , touch and feel in the computer system. It includes input devices, output devices, storage devices, central processing unit etc . All the individual components inside system unit such as power supply, motherboard, BIOS, expansion slots, Rom and chips, ethernet card, video card, sound card, hard diskdrive, floppy disk drive etc are also computer hardware.

The basic building blocks of hardware existing in all computer system are central processing unit, memory unit, input unit and output unit. The person who is involvedin the design and maintenance of computer hardware is known as haredware engineer.

Motherboard:

Motherboard is the core of the comuter. It is the main circuit board in which many internal devces such as video card, sound card, newmory, CPU and other devices are attached.

Motherboard is a fiberglass with a printed circuit board (PCB ) on its surface the pkrinted. Motherboard is also  a part of the processing unit. The most common components of the motherboard are Buses, ROM BIOS, RAM Chip, System Clock, CMOS BAttery, Central Processing Unit ( CPU),Ethernet Card, TV Card, Display Card, Sound Card, Expansion Slots

Memory unit

Memory Unit:

This part of CPU consists of the tiny space CPU-registers. These registers are used to input intermediated data during processing.

Output unit

                The output unit performs work just the reverse of the input unit. It intakes the information resulted from the processing unit, and present it to the user in human readable form. Output  devices such as monitor, printer, speaker etc forms the output unit. The output produced by the monitor is soft copy output because the output cannot be touched but can be seen. Whereas, the output produced by printer and plotter is hardcopy output because output because output comes in a paper form which can be touched.

                Storage Unit

                The storage unit performs the task of storing the data and instruction. There are basically two classes of storage unit. they are primary storage also called primary memory and the secondary storage also called secondary memory.

Primary Memory

                This unit is a temporary storage in the computer. It holds currently running programs, data and instructions. RAM ( Random Access Memory) ROM (Read Only Memory )are the primary memory of computer. In many cases primary memory is considered as the part of processing unit.

Secondary Memory

                This class of storage unit stores the data and instructions permanently that they are easily accessible in the future. It is also used to record the processed results. Several secondary storage media such as hard disk, floppy disk, zip disk etc form a storage unit.

computer system

Computer  System

Computer system is a combination of number of physical parts which are arranged is such a way that they achieve a common objective. Computer system can be divided into number of sub system which can work individually.

The common sub-system in a computer system are input unit, processing unit, processing unit, output unit, and storage unit. These components are called sub - systems because several other smaller components are involved in building up each of these units.

Computer system is a combination of input unit, processing unit, output unit and storage unit which work in and storage unit, which work in co-ordination with each order so as to form the single functional computer.

The basic operation f a computer are input, processing, output and storage which are performed by respective units of a computer system.

Input unit:

Input unit reads the data a and instructions form the user converts them into computer understandable from and transmit it to the processing unit of computer. It act s as a communication channel between user and the computer. Many input devices such as keyboard, mouse, joystick, light pen etc. forms an input unit. They read different form of input and converts those input into binary codes which is understood by computer.

Processing unit

Processing unit is commonly known as central processing unit.

CPU is the main processing unit which perform s ll the calculation and directs  and controls all the units of the computer system.

ALU: This units performs all the arithmetic operations such as addition, subtraction, multiplication and division.

CU: Known as control unit It manages all the computer system.