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MEMORY
Memory is a type of component of computer system, which stores of all the data, instructions and programs of the computer system. Now computer systems have large memory space by which computer can store big programs or big amount of data. Memory of a computer is like a checkerboard where each square holds one byte of the data. Each square has it's own address like a post office box and can be manipulated. When data is entered into the memory of the computer, the previous contents in the square are lost. Thus, the present data can be processed and the results can be had on the output devices. In the execution of all programs, data processing take place in the memory. The contents of any byte can be compared, calculated and copied independently. The space of memory is measured in Bits, Bytes, Kilobytes, Megabytes, Gigabytes, which are the units of memory measurement. The memory of computer is more like a predefined working place, where it temporarily, keeps information and data to facilitate it's performance. When the task is perfored, it clears its memory and then memory space is available for the next task to be performed. When the power is switched off, everything stores in the memory gets erased and cannot be recalled, if we did not save it.
Units of Memory
Computer works by electrical impulses. Hence, the information is represented in binary numbers inside a computer. Binary system uses only two digits '0' and '1'. The memory of a computer contains 1 bit of data. The combination of 8 bits form 1 byte. Each byte represents one character. For ex., 'LIFE' , it is a set of bits processed as a unit. 'LIFE' word length is generally in a range of 8 to 64 bits. A word of 16 bits size can also be called as a 2 bytes word.
Generally, Micro computers and Personal computers uses the range of - 8/16/32 bits, Mini computers uses - the range of - 32 bits and Mainframe computers uses - 64 bits. A 16 bit machine is slower than a 32 bit word.
A 16 bit machine is slower than a 32 bit word. Most microprocessors based modern computers are 16 bits or 32 bits word. Bit is the smallest unit for memory measurement. A bit is a place where where one binary digit (0 and 1) can be placed. The storage capacity of a computer memory is expressed in the term of Kilobytes, Megabytes, Gigabytes and Terabytes.There are two types of computer memory :
1. Primary memory ( i.e., RAM & ROM )
2. Secondary memory ( i.e., Hard Disk, Pen drive, CD ROM, Memory card etc. )
The internal memory is the in-built memory where CPU (Central Processing Unit) holds the programs and data being manipulated. It is used for 4 purposes out of which 3 are related to data processing.
1. Data is hold by input storage space while it is being processed.
2. A working storage space holds data while it is being processed and intermediate results of this processing are made.
3. A program storage area holds the processing instructions.
4. An output area holds the finished result of the processing operations until they are ready for release.
The separate area which is used for 4 purpose are not fixed. They vary from application to applications. This memory inside a computer is also Internal memory. The primary memory is divided into two parts :
1. ROM ( Read Only Memory )
2. RAM ( Random Access Memory )
PROM(Programmable Read Only Memory)
Programmable Read Only Memory (PROM) is a programmable chip, which means that user can write programs in a PROM. It's contents are altered by users.
EPROM(Erasable Programmable Read Only Memory)
Erasable Programmable Read Only Memory (EPROM) control chip can be erased by removing it from the CPU (Central Processing Unit) and exposing it to high intensity, shortwave, ultraviolet light for 10 to 20 minutes.
EEPROM(Electrically Erasable Programmable Read Only Memory)
1. Primary memory ( i.e., RAM & ROM )
2. Secondary memory ( i.e., Hard Disk, Pen drive, CD ROM, Memory card etc. )
Primary memory
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1. Data is hold by input storage space while it is being processed.
2. A working storage space holds data while it is being processed and intermediate results of this processing are made.
3. A program storage area holds the processing instructions.
4. An output area holds the finished result of the processing operations until they are ready for release.
The separate area which is used for 4 purpose are not fixed. They vary from application to applications. This memory inside a computer is also Internal memory. The primary memory is divided into two parts :
1. ROM ( Read Only Memory )
2. RAM ( Random Access Memory )
Read Only Memory ( ROM )
Read Only Memory is the non-volatile memory, which means these chips return the stored data even when the power goes off. Information once store remains fixed i.e., it cannot be change. That is why ROM can only be read and used. It contains micro-programs. It also contain a set of start up instructions. The content of ROM are provided by the manufacturers. Thus, the contents cannot be changed. Read Only Memory is also devided into following categories :- PROM
- EPROM
- EEPROM
PROM(Programmable Read Only Memory)
Programmable Read Only Memory (PROM) is a programmable chip, which means that user can write programs in a PROM. It's contents are altered by users.
EPROM(Erasable Programmable Read Only Memory)
Erasable Programmable Read Only Memory (EPROM) control chip can be erased by removing it from the CPU (Central Processing Unit) and exposing it to high intensity, shortwave, ultraviolet light for 10 to 20 minutes.
EEPROM(Electrically Erasable Programmable Read Only Memory)
This type of ROM can be programmed and erased by electrical signals. This is an erasable
and programmable.
1.Dynamic RAM
2.Static RAM
A dynamic RAM loses its stored information in a very short time even through the power supply is on, as it gets removed periodically. While Static RAM can retain information as much as the power supply is on.
The secondary memory is the external memory of the computer. When this temporary information is to be stored permanently or semi-permanently, external memory is used,i.e., it is stored on different storages devices like Hard Disk, CD ROM, Pen Drive etc. When you switch off the computer, the data preserved on the secondary memory is not deleted but it is saved permanently. There are various devices used as the secondary storage devices and they vary depending on their capacity and prices so as per requirement you can choose a secondary mem9ory device for saving your work.
and programmable.
RAM(Random Access Memory)
The primary memory that can be read from as well as written too is called RAM(Random Access Memory). This is a volatile memory of computer and the program can select at random and use any of the storage locations on this chip to directly storage and retrieve data and instructions. It works as a central memory of computers. If the power goes off, the data in the RAM chip get lost. There are two types of RAM (Read Only Memory) :-1.Dynamic RAM
2.Static RAM
A dynamic RAM loses its stored information in a very short time even through the power supply is on, as it gets removed periodically. While Static RAM can retain information as much as the power supply is on.
Secondary Memory
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