Computer Memory

                                          

     MemoryMemory is a place where we can store data, instructions and results temporarily or permanently.
Memory can be classified into two: Primary memory and Secondary memory.Ö       Primary memory holds data, intermediate results and results of ongoing jobs temporarily.
Ö       Secondary memory on the other hand holds data and information permanently.
Work to do:-1) different memory measuring unitsPrimary storage Or Primary MemoryPrimary memory is a semiconductor memory that is accessed directly by the CPU. It iscapable of sending and receiving data at high speed. There are mainly 3 types of Primary Memoryi)RAM  ii)ROM   iii) Cache Memory.1.RAM :- Random Access MemoryRAM refers to the main memory that microprocessor can read from and write to. Data can be stored andretrieved at random from anywhere within the RAM, no matter where the data is. Data or instructions to beprocessed by the CPU must be placed in the RAM. , RAM is a volatile memory because the  contents of RAM are lost when power is switched off. Eg:-1 GB RAM,2 GB RAM etc.. The speed of a RAM refers to how fast the data in memory is accessed. It is measured in Mega Hertz (MHz). When a computer is in use, its RAM contains the following:1. The operating system software.2. The application software currently being used.3. Any data that is being processed2. Read Only Memory (ROM)•        ROM is a permanent memory that can perform only read operations and its contents cannot be easily altered. ROM is non-volatile; the contents are retained even after the power is switched off. ROM is used in most computers to hold a small, special piece of 'boot up' program known as Basic Input Output System (BIOS).This software runs when the computer is switched on or 'boots up'. It checks the computer's hardware and then loads the operating system. It is slower than RAM.
 There are some modified types of ROM that include:1. PROM - Programmable ROM which can be programmed only once. PROMs are programmed at the time  of manufacture.2. EPROM - Erasable Programmable ROM that can be erased using ultra violetradiation and can be programmed using special electronic circuits.
3. EEPROM - Electrically Erasable Programmable ROM which can be erased andrewritten electrically       Work to do :- 2). Comparison between RAM and ROM3.

Cache memoryCache memory is a small and fast memory between the processor and RAM (main memory). Frequently accessed data, instructions, intermediate results, etc. are stored in cache memory for quick access. When the processor needs to read from or write to a location in RAM, it first checks whether a copy of that data is in the cache. If so, the processor immediately reads the cache, which is much faster than reading from RAM. Cache is more expensive than RAM, but it is worth using it in order to maximise system performance. Commonly used cache memories and their capacities are Level 1 Cache (128 KB), Level 2 Cache (1 MB), Level 3 Cache (8 MB) and Level 4 Cache (128 MB)