Computers – A Gateway to Information(Memory)
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Memory consists of electronic components that store instructions, data, and processing results. It comes in two types - primary and secondary memory. Primary memory (RAM) is directly accessible by the CPU and is volatile, while secondary memory (hard disks, USB drives, etc.) provides non-volatile but slower storage. The memory hierarchy balances speed, space, and cost, with primary memory being faster but more expensive and limited than secondary memory.
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Computers – A Gateway to Information(Memory)
- 1. Memory
- 2. Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data Stores three basic categories of items: introduction to computers. Lec 2 2 The operating system and other system software Application programs Data being processed and the resulting information
- 3. a collection of cells, each with a unique physical/memory address Each cell can hold one byte or 8 bits 101 102 103 201 301 202 203 302 303 With one by we can represent one character in ASCII Code Example: “A” is 65 in ASCII code and 01000001 in binary representation
- 4. Each location in memory has an address Memory size is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB) introduction to computers. Lec 2 4 Page 223 Figure 4-17
- 5. Access time is the amount of time it takes the processor to read from memory ◦ Measured in nanoseconds introduction to computers. Lec 2 5 Page 229 Figures 4-24 – 4-25
- 6. There are two kinds of computer memory: primary and secondary. Primary memory is accessible directly by the processing unit. Mathematics Department 6
- 7. RAM chips usually reside on a memory module and are inserted into memory slots introduction to computers. Lec 2 7
- 8. The amount of RAM necessary in a computer often depends on the types of software you plan to use introduction to computers. Lec 2 8 Page 226 Figure 4-21
- 9. Holds instructions and data needed for programs that are currently running RAM is usually a volatile type of memory Contents of RAM are lost when power is turned off Sli de 1- 9
- 10. RAM: random access memory ◦ SRAM: static RAM No need to be refreshed ◦ DRAM: dynamic RAM Need to be refreshed periodically Main memory ◦ SDRAM (Synchronous DRAM) ◦ EDRAM (Enhanced DRAM) ◦ EDO (Extended Data Out) ◦ FLASH RAM ◦ Ferroelectric RAM
- 11. Primary Memory is referred to as random access memory (RAM) because it is possible to randomly select and use any location of the memory directly store and retrieve data. It takes same time to any address of the memory as the first address. It is also called read/write memory 11
- 12. The storage of data and instructions inside the primary storage is temporary. It disappears from RAM as soon as the power to the computer is switched off. The memories, which loose their content on failure of power supply, are known as volatile memories Mathematics Department 12
- 13. There is another memory in computer, which is called Read Only Memory (ROM). The storage of program and data in the ROM is permanent. The ROM stores some standard processing programs supplied by the manufacturers to operate the computer. The ROM can only be read by the CPU but it cannot be changed. Mathematics Department 13
- 14. The basic input/output program is stored in the ROM that examines and initializes various equipment attached to the PC when the switch is made ON. The memories, which do not loose their content on failure of power supply, are known as non-volatile memories. ROM is non-volatile memory. Mathematics Department 14
- 15. PROM is another type of primary memory in computer, which is called Programmable Read Only Memory (PROM). You know that it is not possible to modify or erase programs stored in ROM, but it is possible for you to store your program in PROM chip. Once the programmes are written it cannot be changed and remain intact even if power is switched off. Programs or instructions written in PROM or ROM cannot be erased or changed. Mathematics Department 15
- 16. EPROM: Erasable Programmable Read Only Memory, which over come the problem of PROM & ROM. EPROM chip can be programmed time and again by erasing the information stored earlier in it. When the EPROM is in use information can only be read. Mathematics Department 16
- 17. The speed of CPU is extremely high compared to the access time of main memory. Therefore the performance of CPU decreases due to the slow speed of main memory. Cache Memory is a small memory chip is attached between CPU and Main memory whose access time is very close to the processing speed of CPU. CACHE memories are accessed much faster than conventional RAM. It is used to store programs or data currently being executed or temporary data Mathematics Department 17
- 18. Memory cache speeds the processes of the computer because it stores frequently used instructions and data 18
- 19. 1-Hard Disk, in computer science, one or more inflexible platters coated with material that allows the magnetic recording of computer data. Hard disks provide faster access to data than floppy disks and are capable of storing much more information. Because platters are rigid, they can be stacked so that one hard-disk drive can access more than one platter. Most hard disks have from two to eight platters. Mathematics Department 19
- 20. Magnetic Tape: Magnetic tapes are used for large computers like mainframe computers where large volume of data is stored for a longer time Floppy Disk: It is similar to magnetic disk discussed above. They are 5.25 inch or 3.5 inch in diameter. They come in single or double density and recorded on one or both surface of the diskette. The capacity of a 5.25- inch floppy is 1.2 mega bytes whereas for 3.5 inch floppy it is 1.44 mega bytes. Mathematics Department 20
- 21. floppy disk * small magnetic data storage disk: a small flexible magnetically coated disk in a rigid plastic case on which data can be stored or retrieved by a computer * a regular floppy disk holds approximately 1.44 megabytes. Mathematics Department 21
- 22. CD-ROM, short for compact disc read-only memory, a rigid plastic disk that stores a large amount of data through the use of laser optics technology. Because they store data optically, CD-ROMs have a much higher memory capacity than computer disks that store data magnetically. However, CD-ROM drives, the devices used to access information on CD-ROMs, can only read information from the disc, not write to it. CD-ROMs can store large amounts of data and so are popular for storing databases and multimedia material. The most common format of CD-ROM holds approximately 630 megabytes . Mathematics Department 22
- 23. A nonvolatile storage medium Contents retained while power is off Hard disk drives are most common ◦ Records data magnetically on a circular disk ◦ Provides fast access to large amounts of data Optical devices store data on CD’s as pits USB flash memory devices ◦ High capacity device plugs into USB port ◦ Portable, reliable, and fits easily in a pocket Sli de 1- 23
- 24. Primary memory is more expensive than secondary memory. The size of primary memory is less than that of secondary memory. Primary memory is faster than secondary memory. Mathematics Department 24
- 25. Memory hierarchy Speed SpaceCost Secondary Memory
- 26. Computer Architecture • Coordination of many levels of abstraction • Under a rapidly changing set of forces • Design, Measurement, and Evaluation I/O systemInstr. Set Proc. Compiler Operating System Application Digital Design Circuit Design Instruction Set Architecture Firmware Datapath & Control Layout